Electrical
Black & Decker Advanced Home Wiring
Source: Black & Decker Advanced Home Wiring.pdf
Source file: Black & Decker Advanced Home Wiring.pdf
AdvAnced
Home Wiring
Updated 4th Edition
DC Circuits • Transfer Switches
Panel Upgrades • Circuit Maps • More
MINNEAPOLIS, MINNESOtA41940 - Advanced Home Wiring_001-063.indd 1 10/10/14 Job: 41940 Title: CSP - Advanced Home Wiring-4th 9:07 AM 9:06 Edition Text Page: 1
First published in 2015 by Cool Springs Press, acquisitions Editor: Mark Johanson
an imprint of Quarto Publishing Group USa Inc., Design Manager: Brad Springer
400 First avenue North, Suite 400, Minneapolis, MN 55401 layout: Danielle Smith-Boldt
Edition Editor: Bruce Barker
© 2015 Quarto Publishing Group USa Inc. Photography: rau + Barber
Photo assistance: adam Esco
all rights reserved. With the exception of quoting brief passages for the pur-
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The information in this book is true and complete to the best of our knowl-
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Cool Springs Press titles are also available at discounts in bulk quantity for
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library of Congress Cataloging-in-Publication Data
ISBN: 978-1-58923-906-1
Digital edition published in 2015
Digital ISBN: 978-1-62788-563-8
Advanced Home Wiring
Created by: The Editors of Creative Publishing international, Inc., in cooperation with BlaCk+DECkEr.
BlaCk+DECkEr and the BlaCk+DECkEr logo are trademarks of The Black & Decker Corporation and are used under license. all rights reserved.
NOTICE TO READERS
For safety, use caution, care, and good judgment when following the procedures described in this book. The publisher
and BlaCk+DECkEr cannot assume responsibility for any damage to property or injury to persons as a result of misuse
of the information provided.
The techniques shown in this book are general techniques for various applications. In some instances, additional
techniques not shown in this book may be required. always follow manufacturers’ instructions included with products,
since deviating from the directions may void warranties. The projects in this book vary widely as to skill levels required:
some may not be appropriate for all do-it-yourselfers, and some may require professional help.
Consult your local building department for information on building permits, codes, and other laws as they apply to
your project.
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Contents
6 30
Advanced Home Wiring
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Wiring Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 68
Planning Your Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Highlights of the National Electrical Code . . . . . . . . . . . . . . . . . 12
Wiring a Room Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Wiring a Kitchen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Circuit Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
86
Common Household Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
GFCI & AFCI Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Replacing a Service Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Grounding & Bonding a Wiring System . . . . . . . . . . . . . . . . . . . 58
Installing a Subpanel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Baseboard Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
94
Wall Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Backup Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Installing a Transfer Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Outbuildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Standalone Solar Lighting System . . . . . . . . . . . . . . . . . . . . . . . 94
Troubleshooting & Repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 101 105
Types of Wall Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Specialty Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Ground-fault (GFCI) & Arc-fault (AFCI) Protection . . . . . . . . . . 120
Junction Boxes, Device Boxes & Enclosures . . . . . . . . . . . . . . 122
113 119
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
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Introduction
E xperienced home electricians understand the need to keep up with changes in the world of wiring. Wiring
projects, and more advanced projects in particular, almost always require a permit from your municipality and
typically an on-site inspection or two as well. If you aren’t up-to-date with wiring codes, there is a likelihood that
your project will not pass inspection. But beyond the practicality of passing inspections, the codes that govern
wiring practices are updated for good reason: they improve safety. And when you’re talking about your own home
and family, that’s worth paying attention to.
This newest edition of BLACK+DECKER Advanced Home Wiring has been reviewed and revised to reflect
the many changes to wiring code published in the 2014 edition of the National Electrical Code (NEC), which is
updated every three years. And this time around there were an unusually high number of changes. They include
the requirement that an available neutral wire be present in every switch box, expansion of the types of circuits
that require AFCI protection, a new prohibition on tying into a garage receptacle, and more. Several of these
changes are reflected in the updated information you’ll find here.
Almost all of the advanced wiring projects featured in this book involve new circuitry, panel upgrades, or
troubleshooting with diagnostic equipment. Among the high-level projects: making a direct-current, solar-electric
circuit; upgrading the grounding and bonding on your new 200-amp or larger home circuit; installing an
automatic transfer switch for your backup power supply; wiring a room addition; and using a multimeter to
precisely locate an open neutral in a home circuit.
Because the projects found in this book are advanced in nature, do not attempt any of them unless you are
confident in your abilities. Consult a professional electrician if you have any concerns—in many cases your best
solution might be to do some of the work yourself, such as pulling new sheathed cable through walls, and to have
the electrical contractor do the other work, such as making the connections. But do keep in mind that home
wiring can be a fun and fascinating pursuit, and successfully accomplishing a major project is personally gratifying
and can also save you substantial amounts of money.
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Wiring Safety
S afety should be the primary concern of anyone
working with electricity. Although most household
electrical repairs are simple and straightforward,
the circuit breaker that controls the circuit you are
servicing. Then check to make sure the power is off by
testing for power with a voltage tester. Tip: Test a live
always use caution and good judgment when working circuit with the voltage tester to verify that it is working
with electrical wiring or devices. Common sense can before you rely on it. Restore power only when the
prevent accidents. repair or replacement project is complete.
The basic rule of electrical safety is: Always turn Follow the safety tips shown on these pages.
off power to the area or device you are working on. At Never attempt an electrical project beyond your skill
the main service panel, remove the fuse or shut off or confidence level.
Shut power OFF at the main service panel or the main Create a circuit index and affix it to the inside of the door to
fuse box before beginning any work. your main service panel. Update it as needed.
Confirm power is OFF by testing at the outlet, switch, or Use only UL-approved electrical parts or devices . These
fixture with a voltage tester. devices have been tested for safety by Underwriters laboratories.
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Wear rubber-soled shoes while working on electrical Use fiberglass or wood ladders when making routine
projects. On damp floors, stand on a rubber mat or dry household repairs near the service mast.
wooden boards.
Extension cords are for temporary use only. Cords must be Breakers and fuses must be compatible with the panel
rated for the intended usage. manufacturer and match the circuit capacity.
Never alter the prongs of a plug to fit a receptacle. If Do not penetrate walls or ceilings without first shutting off
possible, install a new grounded receptacle. electrical power to the circuits that may be hidden.
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Planning Your Project
C areful planning of a wiring project ensures you
will have plenty of power for present and future
needs. Whether you are adding circuits in a room
A large wiring project adds a considerable load
to your main electrical service. In about 25 percent
of all homes, some type of service upgrade is needed
addition, wiring a remodeled kitchen, or adding an before new wiring can be installed. For example, many
outdoor circuit, consider all possible ways the space homeowners will need to replace an older 60-amp
might be used, and plan for enough electrical service electrical service with a new service rated for 100
to meet peak needs. amps or more. This is a job for a licensed electrician
For example, when wiring a room addition, but is well worth the investment. In other cases, the
remember that the way a room is used can change. existing main service provides adequate power, but
In a room used as a spare bedroom, a single 15-amp the main circuit breaker panel is too full to hold any
circuit provides plenty of power, but if you ever choose new circuit breakers. In this case it is necessary to
to convert the same room to a family recreation space, install a circuit breaker subpanel to provide room for
you will need additional circuits. hooking up added circuits. Installing a subpanel is a
When wiring a remodeled kitchen, it is a good idea job most homeowners can do themselves (see pages
to install circuits for an electric oven and countertop 65 to 67).
range, even if you do not have these electric appliances. This chapter gives an easy five-step method
Installing these circuits now makes it easy to convert for determining your electrical needs and planning
from gas to electric appliances at a later date. new circuits.
■ Five Steps for Planning a Wiring Project
1 2
Examine your main service panel (see page 10). The Learn about codes (see pages 11 to 13). The National
amp rating of the electrical service and the size of the circuit Electrical Code (NEC), and local electrical codes and building
breaker panel will help you determine if a service upgrade codes, provide guidelines for determining how much power
is needed. and how many circuits your home needs. Your local electrical
inspector can tell you which regulations apply to your job.
8 ■ ADvANCED
AdvAnced HomE
Home WIRINg
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3 4
Prepare for inspections (see pages 14 to 15). remem- Evaluate electrical loads (see pages 16 to 19). New circuits
ber that your work must be reviewed by your local electrical put an added load on your electrical service. Make sure that
inspector. When planning your wiring project, always follow the the total load of the existing wiring and the planned new
inspector’s guidelines for quality workmanship. circuits does not exceed the service capacity or the capacity of
the panel.
5
Draw a wiring diagram and get a permit (see pages 20 to 21). This wiring plan will help you organize your work.
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■ Examine Your Main Service Panel
The first step in planning a new wiring project is to the main service helps you determine if you need a
look in your main circuit breaker panel and find the service upgrade.
size of the service by reading the amperage rating on Also look for open circuit breaker slots in the
the main circuit breaker. As you plan new circuits panel. The number of open slots will determine if you
and evaluate electrical loads, knowing the size of need to add a circuit breaker subpanel.
Main
circuit
breaker
Find the service size by opening the main service panel and Older service panels use fuses instead of circuit breakers.
reading the amp rating printed on the main circuit breaker. Have an electrician replace this type of panel with a circuit
In most cases, 100-amp service provides enough power to breaker panel that provides enough power and enough open
handle the added loads of projects such as the ones shown breaker slots for the new circuits you are planning.
in this book. a service rated for 60 amps or less should
be upgraded. Note: In some homes the main circuit breaker is
located in a separate box.
Expandable
Not expandable
Look for open circuit breaker slots in the main circuit breaker panel or in a circuit breaker subpanel, if your home already has
one. You will need one open slot for each 120-volt circuit you plan to install and two slots for each 240-volt circuit. If your main
circuit breaker panel has no open breaker slots, install a subpanel (see pages 65 to 67) to provide room for connecting new circuits.
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■ Learn About Codes
To ensure public safety, your community requires that will expect you to understand the local guidelines as
you get a permit to install new wiring and have the well as a few basic NEC requirements.
work reviewed by an inspector. Electrical inspectors The NEC is a set of standards that provides
use the National Electrical Code (NEC) as the primary minimum safety requirements for wiring installations.
authority for evaluating wiring, but they also follow the It is revised every three years. The national code
local building code and electrical code standards. requirements for the projects shown in this book are
most communities use a version of the NEC thoroughly explained on the following pages. For more
that is not the most current version. Also, many information, you can find copies of the current NEC,
communities make amendments to the NEC, and as well as a number of excellent handbooks based on
these amendments may affect your work. the NEC, at libraries and bookstores.
As you begin planning new circuits, call or visit In addition to being the final authority of code
your local electrical inspector and discuss the project requirements, inspectors are electrical professionals
with him or her. The inspector can tell you which of with years of experience. Although they have busy
the national and local code requirements apply to schedules, most inspectors are happy to answer
your job and may give you a packet of information questions and help you design well-planned circuits.
summarizing these regulations. Later, when you
apply to the inspector for a work permit, he or she
■ Basic Electrical Code Requirements
Switch-controlled light fixture
More
than 24"
Dedicated appliance circuit
12 ft. maximum
Electrical code requirements for living areas: living areas need at least one 15-amp or 20-amp basic lighting/receptacle
circuit for each 600 sq. ft. of living space and should have a dedicated circuit for each type of permanent appliance, such as an air
conditioner, or a group of baseboard heaters. receptacles on basic lighting/receptacle circuits should be spaced no more than 12
ft. apart. Many electricians and electrical inspectors recommend even closer spacing. any wall more than 24" wide also needs a
receptacle. Every room should have a wall switch at the point of entry to control either a ceiling or wall-mounted light or plug-in
lamp. kitchens and bathrooms must have a ceiling or wall-mounted light fixture.
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Highlights of the National Electrical Code ▸
BY MATERIAL Switches
Panels • Use a switch‑controlled receptacle in rooms without a
• Maintain a minimum 30" wide by 36" deep of built-in light fixture operated by a wall switch.
clearance in front of the panel. • Use three‑way switches at the top and bottom on
• Match the amperage rating of the circuit when stairways with six risers or more.
replacing fuses. • Use switches with grounding screws with plastic
• Use handle ties on all 240‑volt breakers and on 120‑ electrical boxes.
volt breakers protecting multi-wire branch circuits. • Locate all wall switches within easy reach of the room
• Close all unused panel openings. entrance and not behind the door.
• Label each fuse and breaker clearly on the panel. • Install a neutral wire in switch boxes.
• Use black or red wires to supply power to switched
Electrical Boxes devices.
• Use boxes that are large enough to accommodate the
number of wires and devices in the box. Receptacles
• Install all junction boxes so they remain accessible. • Install receptacles on all walls 24" wide or greater.
• Leave no gaps greater than 1⁄8" between wallboard and • Install receptacles so a 6‑ft. cord can be plugged in
the front of electrical boxes. from any point along a wall or every 12 ft. along a wall.
• Place receptacle boxes flush with • Include receptacles in any hallway that is 10 ft. long
combustible surfaces. or longer.
• Leave a minimum of 3" of usable cable or wire • Use three‑slot, grounded receptacles for all 15‑ or
extending past the front of the electrical box. 20-amp, 120-volt branch circuits.
• Include a switch‑controlled receptacle in rooms
Wires & Cables without a built-in light fixture operated by a wall switch.
• Use wires that are large enough for the amperage • Install GFCI‑protected circuits in bathrooms, kitchens,
rating of the circuit. garages, crawl spaces, unfinished basements, and
• Drill holes at least 2" from the edges of joists. Do not outdoor receptacle locations.
attach cables to the bottom edge of joists.
• Do not run cables diagonally between Light Fixtures
framing members. • Use mounting straps that are anchored to the
• Use nail plates to protect cable that is run through electrical boxes to mount ceiling fixtures.
holes drilled or cut into studs less than 11⁄4" from the • Keep non‑IC‑rated recessed light fixtures 3" from
front edge of a stud. insulation and 1⁄2" from combustibles.
• Do not crimp cables sharply. • Include at least one switch‑operated lighting outlet in
• Contain spliced wires or connections entirely in a every room.
plastic or metal electrical box.
• Use wire connectors to join wires. Grounding
• Use staples to fasten cables within 8" of an electrical • Ground receptacles by connecting receptacle
box and every 54" along its run. grounding screws to the circuit grounding wires.
• Leave a minimum 1⁄4" (maximum 1") of sheathing • Use switches with grounding screws whenever
where cables enter an electrical box. possible. always ground switches installed in
• Clamp cables and wires to electrical boxes with plastic electrical boxes and all switches in kitchens,
approved clamps. No clamp is necessary for one-gang bathrooms, and basements.
plastic boxes if cables are stapled within 8".
• Connect only a single wire to a single screw
terminal. Use pigtails to join more than one wire to a
screw terminal.
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BY ROOM Living, Entertainment, Bedrooms
Kitchens/Dining Rooms • Install at least one 15‑ or 20‑amp lighting/receptacle
• Install at least two 20‑amp small appliance receptacle circuit for each 600 sq. ft. of living space.
circuits. • Install a dedicated circuit for each permanent
• Install dedicated 15‑amp, 120‑volt circuits for dish‑ appliance, such as an air conditioner or group of
washers and food disposals (required by many local electric baseboard heaters.
codes). • Use electrical boxes listed and labeled to support
• Install GFCI protection for all countertop receptacles; ceiling fans.
receptacles behind fixed appliances do not need to be • Include receptacles on walls 24" wide or more.
GFCI protected. • Space receptacles on walls in living and sleeping
• Position receptacles for appliances that will be rooms a maximum of 12 ft. apart.
installed within cabinets, such as microwaves or • Check with your local electrical inspector about
food disposals, according to the manufacturer’s requirements for installing smoke and carbon
instructions. monoxide alarms during remodeling.
• Include receptacles on all counters wider than 12".
• Space receptacles a maximum of 48" apart above Outdoors
countertops and closer together in areas where many • Check for underground utilities before digging.
appliances will be used. • Use UF cable or other wiring approved for wet
• Locate receptacles on the wall above the countertop locations for outdoor wiring.
not more than 20" above the countertop. • Run cable and wires in schedule 80 PVC plastic and
• Install at least one receptacle not more than 12" below other approved conduit, as required by local code.
the countertop on islands and peninsulas that are 12" • Install in‑use rated weatherproof receptacle covers.
× 24" or greater. • Bury cables and wires run in conduit at least 18" deep;
• Do not connect lights to the small appliance receptacle cable not in conduit must be buried at least 24" deep.
circuits. • Use weatherproof electrical boxes with
• Install at least one wall or ceiling‑mounted light fixture. watertight covers.
• Install GFCI‑protected circuits for receptacles.
Bathrooms • Support boxes that are not attached to a building and
• Install a separate 20‑amp GFCI‑protected circuit only that contain switches or receptacles using at least two
for bathroom receptacles. pieces of conduit. Secure the conduit not more than
• Ground switches in bathrooms. 18 feet from the box. locate the box at least 12" above
• Install at least one receptacle not more than 36" from the ground.
each sink.
• Install at least one ceiling‑ or wall‑mounted light fixture. Stairs/Hallways
• Use three‑way switches at the top and bottom on
Utility/Laundry Rooms stairways with six risers or more.
• Install a separate 20‑amp circuit for a • Include receptacles in any hallway that is 10 ft. long or
washing machine. longer.
• Install approved conduit for wiring in unfinished rooms. • Position stairway lights so each step and landing is
• Use GFCI‑protected circuits for 120‑volt receptacles illuminated.
within 6 feet from a sink (including the washing
machine receptacle).
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■ Prepare for Inspections
Electrical inspectors who issue the work permit At the final inspection, inspectors check random
for your wiring project will also visit your home to boxes to make sure the wire connections are correct.
review the work. make sure to allow time for these If they see good workmanship at the selected boxes,
inspections as you plan the project. For most projects, the inspection will be over quickly. However, if they
inspectors make two visits. spot a problem, inspectors may choose to inspect
The first inspection, called the rough-in, is done every connection.
after the cables are run between the boxes but before Inspectors have busy schedules, so it is a
the insulation, wallboard, switches, and fixtures are good idea to arrange for an inspection several days
installed. The second inspection, called the final, is in advance. In addition to basic compliance with
done after the walls and ceilings are finished and all code, inspectors expect your work to meet their
electrical connections are made. own standards for quality. When you apply for a
When preparing for the rough-in inspection, make work permit, make sure you understand what the
sure the area is neat. Sweep up sawdust and clean up inspectors will look for during inspections.
any pieces of scrap wire or cable insulation. Before You cannot put new circuits into use legally until
inspecting the boxes and cables, inspectors will check an inspector approves them at the final inspection. If
to make sure all plumbing and other mechanical work you have planned carefully and done your work well,
is completed. Some electrical inspectors will ask to electrical inspections are routine visits that give you
see your building and plumbing permits. confidence in your own skills.
Inspectors may measure to see that
electrical boxes are mounted at consistent
heights. Height may not be dictated by
code, but consistency is a sign of good
Cable workmanship. Measured from the center
8" maximum staple of the boxes, receptacles in living areas
typically are located 12" above the
finished floor and switches at 48". For
special circumstances, inspectors allow
you to alter these measurements. For
example, you can install switches at 36"
41/2 ft.
above the floor in a child’s bedroom,
or set receptacles at 24" to make them
more convenient for someone using
a wheelchair.
48" Cable
staple Inspectors will check cables to see
that they are anchored by cable staples
driven within 8" of each box and every
41⁄2 ft. thereafter when they run along
studs. When bending cables, form the wire
in a smooth curve. Do not crimp cables
Smooth sharply or install them diagonally between
curve framing members. Some inspectors
About 20" specify that cables running between
12" receptacle boxes should be about 20"
above the floor.
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■ What Inspectors Look for
¼" sheathing, minimum
6" to end of wire
1/2" wallboard
Wall surface
Electrical box faces should extend past the front of framing members so the boxes will be flush with finished walls (left).
Inspectors will check to see that all boxes are large enough for the wires they contain. Cables should be cut and stripped back so
that at least 3" of usable length extends past the front of the box and so that at least 1⁄4" of sheathing reaches into the box (right).
label all cables to show which circuits they serve: inspectors recognize this as a mark of careful work. The labels also simplify the
final hookups after the wallboard is installed.
Is your Receptacle Spacing Correct? ▸
3 ft.sliding 3 ft. fixed 2 ft. 4 ft.
6 ft. door door
6 ft.
2 ft. 6 ft. 1 ft.
6 ft. 4 ft.
1 ft.
3 ft.
Refrigerator
1 ft.
6 ft. 1 ft.
3 ft.
5 ft. 6 ft. Island
1 ft. 6 ft. 2 ft.
Illo 299
CG_Codes
Example of receptacle spacing requirements in a
06-15-2009
typical room. Measure receptacle spacing distance along
the wall line. Install receptacles along partial height walls 4 ft.
and along balcony guards in lofts and similar areas. 1 ft. 4 ft.
Illo 302 spacing in a
Example of countertop receptacle
2 ft. 2 ft. 2.5 ft.
typical kitchen (right). CG_Codes
06-15-2009
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■ Evaluate Electrical Loads
Before drawing a plan and applying for a work permit,
make sure your home’s electrical service provides
enough power to handle the added load of the new
circuits. In a safe wiring system, the current drawn
by fixtures and appliances never exceeds the main
service capacity.
To evaluate electrical loads, use whatever
evaluation method is recommended by your electrical
inspector. Include the load for all existing wiring as
well as that for proposed new wiring when making
your evaluation.
most of the light fixtures and plug-in appliances
in your home are evaluated as part of general
allowances for basic lighting/receptacle circuits and
small-appliance circuits. However, appliances that
are permanently installed require their own dedicated
circuits. The electrical loads for these appliances are
added in separately when evaluating wiring.
If your evaluation shows that the load exceeds the
main service capacity, you must have an electrician
upgrade the main service before you can install new
wiring. An electrical service upgrade is a worthwhile
investment that improves the value of your home
and provides plenty of power for present and future
wiring projects.
Amperage ▸
AMPS × VoltS totAl CAPACItY SAfE CAPACItY
15 A × 120 V = 1,800 watts 1,440 watts
20 A × 120 V = 2,400 watts 1,920 watts
25 A × 120 V = 3,000 watts 2,400 watts
30 A × 120 V = 3,600 watts 2,880 watts
20 A × 240 V = 4,800 watts 3,840 watts
30 A × 240 V = 7,200 watts 5,760 watts
Amperage rating can be used to find the wattage of an
appliance. Multiply the amperage by the voltage of the
circuit. For example, a 13-amp, 120-volt circular saw is
rated for 1,560 watts.
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■ Calculating Loads
Nameplate
Add 1,500 watts for each small appliance circuit required If the nameplate gives the rating in kilowatts, find the
by the local electrical code. In most communities, three such watts by multiplying kilowatts times 1,000. If an appliance
circuits are required—two in the kitchen and one for the lists only amps, find watts by multiplying the amps times the
laundry—for a total of 4,500 watts. No further calculations are voltage—either 120 or 240 volts.
needed for appliances that plug into small-appliance or basic
lighting/receptacle circuits.
fixed Devices ▸
Do not connect one or more fixed devices that in
total exceed 50 percent of a multiple outlet branch
circuit’s amperage rating. Fixed devices do not
include light fixtures. This means that that all fixed
devices (such as a permanently wired disposal or hot
water circulating pump) on a multiple outlet branch
circuit may not exceed 7.5 amps (about 900 watts)
on a 15-amp multiple outlet branch circuit and may
not exceed 10 amps (about 1,200 watts) on a 20-amp
multiple outlet branch circuit.
Air-conditioning and heating appliances are not used at the
same time, so figure in only the larger of these two numbers
when evaluating your home’s electrical load.
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■ Locating Wattage
Nameplate
Nameplate
Light bulb wattage ratings are Electric water heaters are permanent Food disposers are considered
printed on the top of the bulb. If a appliances that require their own permanent appliances and may require
light fixture has more than one bulb, dedicated 30-amp, 240-volt circuits. their own dedicated 15-amp, 120-volt
remember to add the wattages of all Most water heaters are rated between circuits. Most disposers are rated
the bulbs to find the total wattage of 3,500 and 4,500 watts. If the nameplate between 500 and 900 watts.
the fixture. lists several wattage ratings, use the
one labeled “Total Connected Wattage”
when figuring electrical loads.
Nameplate
Nameplate
Nameplate
Dishwashers installed permanently Electric ranges can be rated for as Microwave ovens are regarded
under a countertop may need a little as 3,000 watts or as much as as permanent appliances. add in its
dedicated 15-amp, 120-volt circuits. 12,000 watts. They require dedicated wattage rating when calculating loads.
Dishwasher ratings are usually between 120/240-volt circuits. Find the exact The nameplate is found on the back
1,000 and 1,500 watts. Portable wattage rating by reading the nameplate of the cabinet or inside the front door.
dishwashers are regarded as part of found inside the oven door or on the Most microwave ovens are rated
small appliance circuits and are not back of the unit. between 500 and 1,200 watts.
added in when figuring loads.
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Nameplate Nameplate
Nameplate
Freezers are permanent appliances Electric clothes dryers are Forced-air furnaces and heat pump
that may need a dedicated 15- or 20- permanent appliances that need air handlers have electric fans and are
amp, 120-volt circuits. Freezer ratings dedicated 30-amp, 120/240-volt circuits. considered permanent appliances. They
are usually between 240 and 480 watts. The wattage rating is printed on the require dedicated 15-amp, 120-volt
But combination refrigerator-freezers nameplate inside the dryer door. Use circuits. Include the fan wattage rating,
rated for 1,000 watts or less are plugged 5,000 watts as a minimum, regardless printed on a nameplate inside the
into small appliance circuits and do not of the printed rating. Washing machines control panel, when figuring wattage
need their own dedicated circuits. The and gas-heat clothes dryers with loads for heating. You should also
nameplate for a freezer is found inside electric tumbler motors do not need include the wattage rating for heat
the door or on the back of the unit, just dedicated circuits. They plug into the pump backup heating coils.
below the door seal. 20-amp small-appliance circuit in the
laundry room.
Nameplate
Nameplate
Nameplate
A central air conditioner requires Window air conditioners, both Electric room heaters that are
a dedicated 240-volt circuit. Estimate 120-volt and 240-volt types, are permanently installed require a
its wattage rating by adding the permanent appliances that require dedicated circuit and must be figured
numbers labeled rla and Fla on the air dedicated circuits. The wattage rating, into the load calculations. Use the
conditioner’s metal plate. Multiply the which can range from 500 to 2,000 maximum wattage rating printed
rla+Fla by 240. watts, is found on the nameplate inside the cover. In general, 240-volt
located inside the front grill. Make sure baseboard-type heaters are rated for
to include all window air conditioners in 180 to 250 watts for each linear foot.
your evaluation.
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■ Draw a Diagram & Obtain a Permit
Drawing a wiring diagram is the last step in planning a basic understanding of the electrical code and
a circuit installation. A detailed wiring diagram helps fundamental wiring skills. Some inspectors ask these
you get a work permit, makes it easy to create a list of questions informally, while others give a short written
materials, and serves as a guide for laying out circuits test. Inspectors may allow you to do some, but not all,
and installing cables and fixtures. Use the circuit of the work. For example, they may ask that all final
maps on pages 30 to 47 as a guide for planning wiring circuit connections at the circuit breaker panel be
configurations and cable runs. Bring the diagram and made by a licensed electrician, while allowing you to
materials list when you visit electrical inspectors to do all other work.
apply for a work permit. A few communities allow you to install wiring
Never install new wiring without following your only when supervised by an electrician. This means
community’s permit and inspection procedure. A work you can still install your own wiring but must hire
permit is not expensive, and it ensures that your work an electrician to apply for the work permit and to
will be reviewed by a qualified inspector. If you install check your work before inspectors review it. The
new wiring without the proper permit, an accident or electrician is held responsible for the quality of
fire traced to faulty wiring could cause your insurance the job.
company to discontinue your policy and can hurt the Remember that it is the inspectors’ responsibility
resale value of your home. to help you do a safe and professional job. Feel free
When electrical inspectors look over your wiring to call them with questions about wiring techniques
diagram, they will ask questions to see if you have or materials.
A detailed wiring diagram and a list of materials is required before electrical inspectors will issue a work permit. If blueprints
exist for the space you are remodeling, start your electrical diagram by tracing the wall outlines from the blueprint. Use standard
electrical symbols (next page) to clearly show all the receptacles, switches, light fixtures, and permanent appliances. Make a copy
of the symbol key and attach it to the wiring diagram for the inspectors’ convenience. Show each cable run, and label its wire size
and circuit amperage.
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■ How to Draw a Wiring Plan
1 2
Draw a scaled diagram of the space you will be wiring, Mark the location of all switches, receptacles, light fixtures,
showing walls, doors, windows, plumbing pipes and fixtures, and and permanent appliances, using the electrical symbols shown
heating and cooling ducts. Find the floor space by multiplying below. Where you locate these devices along the cable run
room length by width, and indicate this on the diagram. determines how they are wired. Use the circuit maps on pages
30 to 47 as a guide for drawing wiring diagrams.
3 4
Draw in cable runs between devices. Indicate cable Identify the wattages for light fixtures and permanent
size and type and the amperage of the circuits. Use a appliances and the type and size of each electrical box. On another
different‑colored pencil for each circuit. sheet of paper, make a detailed list of all materials you will use.
Electrical Symbol Key ▸
(copy this key and attach it to your wiring plan)
240‑volt Switched Junction box Ceiling fan
receptacle receptacle
Electric door
Isolated ground Weatherproof Ceiling opener
receptacle receptacle pull switch
Low‑voltage
Duplex Surface‑mounted transformer
receptacle Thermostat light fixture
Television
240‑volt Pilot‑light Recessed jack
dryer receptacle switch light fixture
Telephone
Singleplex Single‑pole Fluorescent outlet
receptacle switch light fixture
Smoke
Fourplex Timer Wall‑mounted dectector
receptacle switch light fixture
Vent fan
GFCI duplex Three‑way Weatherproof
receptacle switch light fixture
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age: 20 Text Page: 21
Wiring a Room Addition
T he photo below shows the circuits you would
likely want to install in a large room addition. This
example shows the framing and wiring of an unfinished
Individual Circuits
#1: Bathroom circuit . This 20-amp dedicated circuit
supplies power to bathroom lights and fans, as well as
attic converted to an office or entertainment room with receptacles that must be GFCI-protected at the box or at the
a bathroom. This room includes a subpanel and five receptacle. as with small appliance circuits in the kitchen, you
new circuits plus telephone and cable-Tv lines. may not tap into this circuit to feed any additional loads.
A wiring project of this sort is a potentially #2: Computer circuit . a15-amp dedicated circuit with
complicated undertaking that can be made simpler isolated ground is recommended, but an individual branch
by breaking the project into convenient steps, and circuit is all that is required by most codes.
finishing one step before moving on to the next. Turn
Circuit breaker subpanel receives power through a
to pages 24 to 25 to see this project represented as a
10-gauge, three-wire feeder cable connected to a 30-amp,
wiring diagram.
14/2 cable
Vent fan
Circuit breaker Vanity
subpanel light
fixture GFCI
GfCI receptacle
12/2 cable
12/2 cable
time & light
Time
fixture switch
14/3 cable
Blower heater
10/3 cable
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240-volt circuit breaker at the main circuit breaker panel. heaters. Depending on the size of your room and the wattage
larger room additions may require a 60-or 100-amp feeder rating of the baseboard heaters, you may need a 30-amp,
circuit breaker. 240-volt heating circuit.
#3: Air-conditioner circuit . This is a 20-amp, 240-volt Telephone outlet is wired with 22-gauge four-wire phone
dedicated circuit. In cooler climates, or in a smaller room, you cable. If your home phone system has two or more separate
may need an air conditioner and circuit rated for only 120 volts. lines, you may need to run a cable with eight wires, commonly
called four-pair cable.
#4: Basic lighting/receptacle circuit . This 15-amp,
120-volt circuit supplies power to most of the fixtures in the Cable television jack is wired with coaxial cable running
bedroom and study areas. from an existing television junction in the utility area.
#5: Heater circuit . This 20-amp, 240-volt circuit supplies
power to the bathroom blower-heater and to the baseboard
14/3 cable
14/3 cabletacle
Phone cable
Coaxial cable
these cables continue
These
through the foreground
wall to complete the
circuits. this
This wall has
12/2 cable been removed for clarity.
14/2 cable
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■ Diagram View
The diagram below shows the layout of the five Circuit #1: a 20-amp, 120-volt circuit serving the bathroom
circuits and the locations of their receptacles, and closet area. Includes: 12/2 NM cable, double-gang box,
switches, fixtures, and devices as shown in the timer switch, single-pole switch, 4" × 4" box with single-gang
adapter plate, two plastic light fixture boxes, vanity light fixture,
photo on the previous pages. The circuits and
closet light fixture, 15-amp single-pole circuit breaker.
receptacles are based on the needs of a 400-sq.-ft.
space. An inspector will want to see a diagram Circuit #2: a 15-amp, 120-volt computer circuit. Includes:
like this one before issuing a permit. After you’ve 14/2 NM cable, single-gang box, 15-amp receptacle, 15-amp
single-pole circuit breaker.
received approval for your addition, the wiring
diagram will serve as your guide as you complete Circuit #3: a 20-amp, 240-volt air-conditioner
your project. circuit. Includes: 12/2 NM cable; single‑gang box;
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20‑amp, 240‑volt receptacle (singleplex style); 20‑amp Circuit #5: a 20-amp, 240-volt circuit that supplies power
double-pole circuit. to three baseboard heaters controlled by a wall thermostat
and to a bathroom blower-heater controlled by a built-in
Circuit #4: a 15-amp, 120-volt basic lighting/receptacle thermostat. Includes: 12/2 NM cable, 750-watt blower heater,
circuit serving most of the fixtures in the bedroom and study single-gang box, line-voltage thermostat, three baseboard
areas. Includes: 14/2 and 14/3 NM cable, two double-gang heaters, 20-amp double-pole circuit breaker.
boxes, fan speed-control switch, dimmer switch, single-pole
switch, two three-way switches, two plastic light fixture boxes, Cable television jack: Coaxial cable with F-connectors,
light fixture for stairway, smoke detector, metal light fixture signal splitter, cable television outlet with mounting brackets.
box with brace bar, ceiling fan with light fixture, 10 single-gang
boxes, 4" × 4" box with single-gang adapter plate, 10 duplex Circuit #6: a 20-amp, 120-volt, GFCI-protected bathroom
receptacles (15-amp), 15-amp single-pole circuit breaker. receptacle circuit for the bathroom. Includes GFCI breaker,
12/2 NM cable, boxes, and 20-amp receptacles.
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Wiring a Kitchen
14/2 cable
12/3 cable
12/2 cable
6/3 cable
14/2 cable
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T he photo at left shows the circuits you would
probably want to install in a total kitchen
remodel. Kitchens require a wide range of electrical
services, from simple 15-amp lighting circuits to
120/240, 50-amp appliance circuits. This kitchen
example has seven circuits, including separate
dedicated circuits for a dishwasher and food disposer.
Some codes allow the disposer and dishwasher to
share a single circuit.
All rough carpentry and plumbing should be
in place before beginning any electrical work. As
always, divide a project of this scale into manageable
steps, and finish one step before moving on. Turn to
pages 28 to 29 to see this project represented as a
wiring diagram.
14/3 cable
Individual Circuits
#1 & #2: Small-appliance circuits . Two 20-amp, 120-volt
circuits supply power to countertop and eating areas for small
appliances. all general-use receptacles must be on these
circuits. One 12/3 cable fed by a 20-amp double-pole breaker
wires both circuits. These circuits share one electrical box with
14/2 cable the disposer circuit (#5) and another with the basic lighting
circuit (#7). Other circuits may also service the area, as with a
14/2 cable dedicated refrigerator circuit.
#3: Range circuit . a 40- or 50-amp, 120/240-volt dedicated
circuit supplies power to the range/ oven appliance. It is wired
with 6/3 copper cable.
12/3 cable
#4: Microwave circuit . It is wired with 12/2 cable.
Microwaves that use less than 300 watts can be installed on a
15-amp circuit or plugged into the small-appliance circuits.
#5: Food disposer/dishwasher circuit . a dedicated
15-amp, 120-volt circuit supplies power to the disposer. It
12/3 cable is wired with 14/2 cable. Some local codes may allow the
disposer to be on the same circuit as the dishwasher if it is a
20-amp circuit.
#6: Basic lighting circuit . a 15-amp, 120-volt
circuit powers the ceiling fixture, recessed fixtures, and
undercabinet task lights. 14/2 and 14/3 cables connect the
14/2 cable fixtures and switches in the circuit. Each task light has a
self-contained switch.
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■ Diagram View
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The diagram at left shows the layout of the seven
circuits and the locations of their receptacles,
switches, fixtures, and devices as shown in the
photo on the previous pages. The circuits and
receptacles are based on the needs of a 175-sq.-ft.
space kitchen. An inspector will want to see a
diagram like this one before issuing a permit. After
you’ve received approval for your addition, the wiring
diagram will serve as your guide as you complete
your project.
Circuits #1 & #2: Two 20-amp, 120-volt small-appliance
circuits wired with one cable. all general-use receptacles must
be on these circuits, and they must be GFCI units. Includes:
two GFCI receptacles rated for 20 amps, five electrical boxes
that are 4" × 4", and 12/3 cable.
Circuit #3: a 50-amp, 120/240-volt dedicated circuit for the
range. Includes: a 4" × 4" box; a 120/240‑volt, 50‑amp range
receptacle; and 6/3 NM copper cable.
Circuit #4: a 20-amp, 120-volt dedicated circuit for
the microwave. Includes: a 20-amp duplex receptacle, a
single-gang box, and 12/2 NM cable.
Circuit #5: a 15-amp, 120-volt dedicated circuit for the food
disposer. Includes: a 15-amp duplex receptacle, a single-pole
switch (installed in a double-gang box with a GFCI receptacle
from the small-appliance circuits), one single-gang box, and
14/2 cable.
Circuit #6: a 15-amp, 120-volt basic lighting circuit serving
all of the lighting needs in the kitchen. Includes: two single-pole
switches, two three-way switches, single-gang box, 4" × 4"
box, triple-gang box (shared with one of the GFCI receptacles
from the small-appliance circuits), plastic light fixture box with
brace, ceiling light fixture, four fluorescent undercabinet light
fixtures, six recessed light fixtures, 14/2 and 14/3 cables.
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to light to fan
tHREE-WIRE CABlE
(NEUtRAl Not USED)
tWo-WIRE CABlE
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Circuit Maps
T he circuit maps on the following pages show
the most common wiring variations for typical
electrical devices. most new wiring you install will
match one or more of the maps shown. Find the maps
that match your situation and use them to plan your
circuit layouts.
The 120-volt circuits shown on the following
pages are wired for 15 amps using 14-gauge wire and
receptacles rated at 15 amps. If you are installing a
20-amp circuit, substitute 12-gauge cables and use
receptacles rated for 15 or 20 amps.
In configurations where a white wire serves as a
hot wire instead of a neutral, both ends of the wire are
coded with black tape to identify it as hot. In addition,
each of the circuit maps shows a box grounding
screw. This grounding screw is required in all metal
boxes, but plastic electrical boxes do not need to
be grounded.
You should remember two new code requirements
when wiring switches. (1) Provide a neutral wire at
every switch box. This may require using 3-wire cable or
two 2-wire cables where you may have used one 2-wire
cable in the past. (2) Use a black or red wire to supply
power from a switch to a light or switched receptacle.
Note: For clarity, all grounding conductors in
the circuit maps are colored green. In practice, the
grounding wires inside sheathed cables usually are
bare copper.
In this chapter:
• Common Household Circuits
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Common Household Circuits
1. 120‑volt Duplex Receptacles
WiReD in sequence
Use this layout to link any number of duplex
receptacles in a basic lighting/receptacle circuit. The
last receptacle in the cable run is connected like
the receptacle shown at the right side of the circuit
map below. All other receptacles are wired like the
receptacle shown on the left side. This configuration or
layout requires two‑wire cables.
2-WIRE CABLE 2-WIRE CABLE
2. GFci Receptacles
(sinGle‑location pRotection)
Use this layout when receptacles are within 6 ft. of a
water source, such as those in kitchens and bathrooms.
To prevent nuisance tripping caused by normal power
surges, GFCIs should be connected only at the line screw
terminal so they protect a single location, not the fixtures
on the load side of the circuit. Requires two‑wire cables.
Where a GFCI must protect other fixtures, use circuit map
3. Remember that bathroom receptacles should usually
be on a dedicated 20‑amp circuit and that all bathroom
receptacles must be GFCI‑protected.
2-WIRE CABLE 2-WIRE CABLE
LOAD silver LOAD brass
LINE silver LINE brass
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Text Page: 32
3 . GFCI RECEPTACLE, SWITCH
& LIGHT FIxTURE (WIRED FOR
MULTIPLE-LOCATION PROTECTION)
In some locations, such as an outdoor circuit, it is
a good idea to connect a gFCI receptacle so it also
provides shock protection to the wires and fixtures
that continue to the end of the circuit. Wires from
the power source are connected to the line screw
terminals; outgoing wires are connected to load
screws. Requires two-wire cables.
2-WIRE CABlE 2-WIRE CABlE 2-WIRE CABlE
loAD silver loAD brass
lINE silver lINE brass
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4 . SINGLE-POLE SWITCH & LIGHT FIxTURE
(LIGHT FIxTURE AT END OF CABLE RUN)
Use this layout for light fixtures in basic lighting/
receptacle circuits throughout the home. It is often
used as an extension to a series of receptacles (circuit
map 1). Requires two-wire cables.
2-WIRE CABlE 2-WIRE CABlE
5 . SINGLE-POLE SWITCH & LIGHT FIxTURE
(SWITCH AT END OF CABLE RUN)
Use this layout, sometimes called a switch loop, where
it is more practical to locate a switch at the end of
the cable run. In the last length 3-wire cable is used
to make a hot conductor available in each direction.
Requires two-wire and three-wire cables.
2-WIRE CABlE 3-WIRE CABlE
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6 . SINGLE-POLE SWITCH & TWO LIGHT
FIxTURES (SWITCH BETWEEN LIGHT
FIxTURES, LIGHT AT START OF CABLE RUN)
Use this layout when you need to control two fixtures
from one single-pole switch and the switch is between
the two lights in the cable run. Power feeds to one of
the lights. Requires two-wire and three-wire cables.
3-WIRE 2-WIRE
2-WIRE CABlE CABlE CABlE
7 . SINGLE-POLE SWITCH & LIGHT FIxTURE,
DUPLEx RECEPTACLE (SWITCH AT START
OF CABLE RUN)
Use this layout to continue a circuit past a switched
light fixture to one or more duplex receptacles. To add
multiple receptacles to the circuit, see circuit map 1.
Requires two-wire and three-wire cables.
2-WIRE CABlE 3-WIRE CABlE 2-WIRE CABlE
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8 . SWITCH-CONTROLLED SPLIT
RECEPTACLE, DUPLEx RECEPTACLE
(SWITCH AT START OF CABLE RUN)
This layout lets you use a wall switch to control a lamp
plugged into a wall receptacle. This configuration
is required by code for any room that does not have
a switch-controlled wall or ceiling fixture. only the
bottom half of the first receptacle is controlled by
the wall switch; the top half of the receptacle and
all additional receptacles on the circuit are always
hot. Requires two-wire and three-wire cables. Some
electricians help people identify switched receptacles
by installing them upside down.
2-WIRE CABlE 3-WIRE CABlE 2-WIRE CABlE
Switched half tab removed
9 . SWITCH-CONTROLLED SPLIT RECEPTACLE
(SWITCH AT END OF CABLE RUN)
Use this switch loop layout to control a split
receptacle (see circuit map 7) from an end-of-run
circuit location. The bottom half of the receptacle
is controlled by the wall switch, while the top half is
always hot. Requires two-wire and three-wire cable.
Some electricians help people identify switched
receptacles by installing them upside down.
2-WIRE CABlE 3-WIRE CABlE
tab removed
Switched half
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10 . SWITCH-CONTROLLED SPLIT
RECEPTACLE, DUPLEx RECEPTACLE
(SPLIT RECEPTACLE AT START OF RUN)
Use this variation of circuit map 7 where it is more
practical to locate a switch-controlled receptacle at the
start of a cable run. only the bottom half of the first
receptacle is controlled by the wall switch; the top
half of the receptacle, and all other receptacles on the
circuit, are always hot. Requires two-wire and three-
wire cables. Some electricians help people identify
switched receptacles by installing them upside down.
2-WIRE CABlE 3-WIRE CABlE
tab removed
Switched
half
2-WIRE CABlE
11 . DOUBLE RECEPTACLE CIRCUIT WITH
SHARED NEUTRAL WIRE (RECEPTACLES
ALTERNATE CIRCUITS)
This layout features two 120-volt circuits wired with
one three-wire cable connected to a double-pole
circuit breaker. The black hot wire powers one
circuit; the red wire powers the other. The white wire
is a shared neutral that serves both circuits. When
wired with 12/2 and 12/3 cable and receptacles
rated for 20 amps, this layout can be used for the
two small-appliance circuits required in a kitchen.
Remember to use a gFCI circuit breaker if you use
this circuit for kitchen counter top receptacles.
Neutral
bus bar
3-WIRE 3-WIRE 3-WIRE 2-WIRE
CABlE CABlE CABlE CABlE
Grounding bus bar
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12 . DOUBLE RECEPTACLE SMALL-
APPLIANCE CIRCUIT WITH GFCIs &
SHARED NEUTRAL WIRE
Use this layout variation of circuit map 10 to wire a
double receptacle circuit when code requires that
some of the receptacles be gFCIs. The gFCIs should
be wired for single-location protection (see circuit map
2). Requires three-wire and two-wire cables.
12/3 12/3 12/3 12/2
line line line line
silver silver silver silver
line line line line
brass brass brass brass
13 . DOUBLE RECEPTACLE SMALL
APPLIANCE CIRCUIT WITH GFCIs &
SEPARATE NEUTRAL WIRES
If the room layout or local codes do not allow for a
shared neutral wire, use this layout instead. The
gFCIs should be wired for single-location protection
(see circuit map 2). Requires two-wire cable.
12/2 12/2 12/2
12/2 12/2 12/2
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14. 120/240‑volt range receptacle
This layout is for a 40‑ or 50‑amp, 120/240‑volt
dedicated appliance circuit wired with 8/3 or 6/3 cable,
as required by code for a large kitchen range. The
black and red circuit wires, connected to a double‑pole
circuit breaker in the circuit breaker panel, each bring
120 volts of power to the setscrew terminals on the
receptacle. The white circuit wire attached to the
neutral bus bar in the circuit breaker panel is connected
to the neutral setscrew terminal on the receptacle.
Grounding Neutral bus bar
bus bar
3-WIRE CABLE
15. 240‑volt BaseBoard
Heaters, tHermostat
This layout is typical for a series of 240‑volt baseboard
heaters controlled by a wall thermostat. Except for
the last heater in the circuit, all heaters are wired as
shown below. The last heater is connected to only
one cable. The sizes of the circuit and cables are
determined by finding the total wattage of all heaters.
Requires two‑wire cable.
Coded for hot
Coded for hot
Baseboard heater
2-WIRE CABLE 2-WIRE
CABLE
Coded for hot 2-WIRE CABLE
From source
To next heater
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age: 38 Text Page: 39
16. DeDicAteD 120‑volt computeR
ciRcuit, isolAteD‑gRounD ReceptAcle
This 15‑amp isolated‑ground circuit provides extra
protection against surges and interference that can
harm electronics. It uses 14/3 cable with the red
wire serving as an extra grounding conductor. The I
red wire is tagged with green tape for identification.
It is connected to the grounding screw on an
isolated‑ground receptacle and runs back to the
grounding bus bar in the circuit breaker panel without
I
touching any other house wiring.
Grounding Neutral
bus bar bus bar
3-WIRE CABLE
Coded for
ground
Silver Brass
Coded for
ground
17. 240‑volt AppliAnce ReceptAcle
This layout represents a 20‑amp, 240‑volt dedicated
appliance circuit wired with 12/2 cable, as required by
code for a large window air conditioner. Receptacles are
available in both singleplex (shown) and duplex styles.
The black and the white circuit wires connected to a
double‑pole breaker each bring 120 volts of power to
the receptacle (combined, they bring 240 volts). The
white wire is tagged with black tape to indicate it is hot.
Coded for hot
2-WIRE CABLE
Grounding
bus bar Coded for hot
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Text Page: 40
18 . GANGED SINGLE-POLE SWITCHES
CONTROLLING SEPARATE LIGHT FIxTURES
This layout lets you place two switches controlled by
the same 120-volt circuit in one double-gang electrical
box. A single-feed cable provides power to both
switches. A similar layout with two feed cables can be
used to place switches from different circuits in the
same box. Requires two-wire cable.
2-WIRE CABlE
2-WIRE CABlE 2-WIRE CABlE
19 . GANGED SWITCHES CONTROLLING
A LIGHT FIxTURE AND A VENT FAN
This layout lets you place two switches controlled by
the same 120-volt circuit in one double-gang electrical
box. A single-feed cable provides power to both
switches. A standard switch controls the light fixture,
and a time-delay switch controls the vent fan.
2-WIRE CABlE
2-WIRE CABlE
2-WIRE
CABlE
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20 . THREE-WAY SWITCHES & LIGHT
FIxTURE (FIxTURE BETWEEN SWITCHES)
This layout for three-way switches lets you control
a light fixture from two locations. Each switch has
one common screw terminal and two traveler screws.
Circuit wires attached to the traveler screws run
between the two switches, and hot wires attached
to the common screws bring current from the power
source and carry it to the light fixture. Requires
parallel runs of 2-wire cable.
2-WIRE CABlE
traveler
2-WIRE CABlE
2-WIRE CABlE
Common
Coded for hot
traveler
Common
21 . THREE-WAY SWITCHES & LIGHT FIxTURE
(FIxTURE AT START OF CABLE RUN)
Use this layout variation of circuit map 19 where
it is more convenient to locate the fixture ahead of
the three-way switches in the cable run. Requires
two-wire and three-wire cables.
traveler
2-WIRE
CABlE 3-WIRE CABlE 2-WIRE CABlE
2-WIRE CABlE
Common
Common
traveler
Coded for hot
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22 . THREE-WAY SWITCHES & LIGHT
FIxTURE (FIxTURE AT END OF CABLE RUN)
This variation of the three-way switch layout (circuit
map 20) is used where it is more practical to locate
the fixture at the end of the cable run. Requires
two-wire and three-wire cables.
3-WIRE
2-WIRE CABlE 2-WIRE CABlE
CABlE
Common traveler
Common
traveler
traveler
23 . THREE-WAY SWITCHES & LIGHT
FIxTURE WITH DUPLEx RECEPTACLE
Use this layout to add a receptacle to a three-way
switch configuration (circuit map 21). Requires
two-wire and parallel runs of two-wire cables.
2-WIRE CABlE 2-WIRE CABlE
Common
Common
Coded
for hot
traveler 2-WIRE CABlE
traveler
2-WIRE CABlE 2-WIRE CABlE
Coded
for hot
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24 . THREE-WAY SWITCHES &
MULTIPLE LIGHT FIxTURES (FIxTURES
BETWEEN SWITCHES)
This is a variation of circuit map 20. Use it to place
multiple light fixtures between two three-way switches
where power comes in at one of the switches.
Requires two- and three-wire cable.
Coded
for hot
2-WIRE 3-WIRE Common
CABlE CABlE
2-WIRE
CABlE
2-WIRE
CABlE
Common 3-WIRE
CABlE
2-WIRE
CABlE
25 . THREE-WAY SWITCHES & MULTIPLE
LIGHT FIxTURES (FIxTURES AT BEGINNING
OF RUN)
This is a variation of circuit map 21. Use it to place
multiple light fixtures at the beginning of a run
controlled by two three-way switches. Power comes in
at the first fixture. Requires two- and three-wire cable.
2-WIRE 3-WIRE 3-WIRE 2-WIRE CABlE
CABlE CABlE CABlE
Common
Coded
for
Common hot
2-WIRE CABlE
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26 . FOUR-WAY SWITCH & LIGHT FIxTURE
(FIxTURE AT START OF CABLE RUN)
This layout lets you control a light fixture from three
locations. The end switches are three-way, and the
middle is four-way. A pair of three-wire cables enter
the box of the four-way switch. The white and red
wires from one cable attach to the top pair of screw
terminals (line 1), and the white and red wires from
the other cable attach to the bottom screw terminals
(line 2). Requires two three-way switches and one
four-way switch and two-wire and three-wire cables.
2-WIRE
2-WIRE 3-WIRE 2-WIRE CABlE
CABlE CABlE CABlE
Coded
for hot
2-WIRE
CABlE
2-WIRE
CABlE
Coded for hot
27 . FOUR-WAY SWITCH & LIGHT FIxTURE
(FIxTURE AT END OF CABLE RUN)
Use this layout variation of circuit map 26 where it is
more practical to locate the fixture at the end of the
cable run. Requires two three-way switches and one
four-way switch and two-wire and three-wire cables.
2-WIRE CABlE 3-WIRE 3-WIRE 2-WIRE
CABlE CABlE CABlE
Common Common
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28 . MULTIPLE FOUR-WAY SWITCHES
CONTROLLING A LIGHT FIxTURE
This alternate variation of the four-way switch layout
(circuit map 27) is used where three or more switches
will control a single fixture. The outer switches are
three-way, and the middle are four-way. Requires two
three-way switches and two four-way switches and
two-wire and three-wire cables.
2-WIRE 3-WIRE 3-WIRE 3-WIRE 2-WIRE
CABlE CABlE CABlE CABlE CABlE
Common Common
29 . FOUR-WAY SWITCHES &
MULTIPLE LIGHT FIxTURES
This variation of the four-way switch layout (circuit
map 26) is used where two or more fixtures will be
controlled from multiple locations in a room. outer
switches are three-way, and the middle switch is a
four-way. Requires two three-way switches and one
four-way switch and two-wire and three-wire cables.
2-WIRE 2-WIRE 2-WIRE
3-WIRE CABlE CABlE
CABlE CABlE
2-WIRE 2-WIRE
3-WIRE CABlE CABlE
CABlE
Coded Coded
for hot for hot
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30 . CEILING FAN/LIGHT FIxTURE CONTROLLED BY GANGED SWITCHES
(FAN AT END OF CABLE RUN)
This layout is for a combination ceiling fan/light fixture controlled by a speed-control switch and dimmer in a
double-gang switch box. Requires two-wire and three-wire cables.
to fan
to light
2-WIRE CABlE 3-WIRE CABlE
31 . CEILING FAN/LIGHT FIxTURE CONTROLLED BY GANGED SWITCHES
(SWITCHES AT END OF CABLE RUN)
Use this switch loop layout variation when it is more practical to install the ganged speed control and dimmer
switches for the ceiling fan at the end of the cable run. Requires two-wire and parallel runs of two-wire cables.
to light to fan
3-WIRE CABlE
(NEUtRAl Not USED)
2-WIRE CABlE 2-WIRE CABlE
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GfCI & AfCI Breakers
U nderstanding the difference between gFCI
(ground-fault circuit interrupter) and AFCI (arc
fault circuit interrupter) is tricky for most homeowners.
tools & Materials ▸
Essentially it comes down to this: Arc-fault interrupters Insulated Combination tool
keep your house from burning down; ground-fault screwdriver AFCI or
interrupters keep people from being electrocuted. Circuit tester gFCI breaker
The National Electric Code (NEC) requires
that an AFCI breaker be installed on most branch
circuits that supply outlets or fixtures in newly
constructed homes. The NEC also requires adding ARC-FAULT CIRCUIT INTERRUPTERS
AFCI protection to these circuits when you add new AFCIs detect arcing (sparks) that can cause
circuits and modify or extend existing circuits. They’re fires between and along damaged wires. AFCI
a prudent precaution in any home, especially if it has protection is required for 15- and 20-amp, 120-
older wiring. AFCI breakers will not interfere with the volt circuits that serve living rooms, family rooms,
operation of gFCI receptacles, so it is safe to install dens, parlors, libraries, dining rooms, bedrooms,
an AFCI breaker on a circuit that contains gFCI sun rooms, kitchens, laundry areas, closets, and
receptacles. For a discussion on codes that concern hallways. AFCI protection is not required for
AFCI and gFCI breakers see pages 120 to 121. circuits serving bathrooms, garages, the exterior
of the home, appliances such as furnaces and
GROUND-FAULT air handlers.
CIRCUIT-INTERRUPTERS The easiest way to provide AFCI protection for
A gFCI is an important safety device that disconnects a circuit is to install an AFCI circuit breaker labeled
a circuit in the event of a ground fault (when current as a “combination” device in the electrical panel.
takes a path other than the neutral back to the panel). The 2014 NEC allows several alternate methods of
on new construction, gFCI protection is required providing AFCI protection, but you should consult
for receptacles in these locations: kitchen counter an electrician before using these alternate methods.
tops, bathrooms, garages, unfinished basements, You should install combination AFCI circuit breakers
crawlspaces, outdoors, within six feet of sinks, and when installing new circuits that require AFCI
in unfinished accessory buildings such as storage protection. You should install either combination AFCI
and work sheds. In general it is a good practice to circuit breakers or AFCI receptacles when you modify,
protect all receptacle and fixture locations that could replace, or extend an existing circuit that requires
encounter damp or wet circumstances. AFCI protection.
AFCI breakers (left) are similar in
appearance to GFCI breakers (right), but
they function differently. aFCI breakers
trip when they sense an arc fault. GFCI
breakers trip when they sense fault
between the hot wire and the ground.
An AFCI-protected
receptacle
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■ How to Install an AFCI or GFCI Breaker
1 2 3
Locate the breaker for the circuit Find the white wire on the circuit Flip the handle of the new aFCI or
you’d like to protect. Turn off the main you want to protect, and remove it from GFCI breaker to OFF. loosen both of
circuit breaker. remove the cover from the neutral bus bar. the breaker’s terminal screws. Connect
the panel, and test to ensure that power the white circuit wire to the breaker
is off. remove the breaker you want terminal labeled PaNEl NEUTral.
to replace from the panel. remove the Connect the black circuit wire to the
black wire from the lOaD terminal of breaker terminal labeled lOaD POWEr.
the breaker.
4 5 6
Connect the new breaker’s coiled Make sure all the connections are Turn the main breaker on . Turn off
white wire to the neutral bus bar on tight . Snap the new breaker into the and unplug all fixtures and appliances
the service panel. bus bar. on the aFCI or GFCI breaker circuit.
Turn the aFCI or GFCI breaker on. Press
the test button. If the breaker is wired
correctly, the breaker trips open. If it
doesn’t trip, check all connections or
consult an electrician. replace the
panel cover.
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Replacing a Service Panel
O nly a generation ago, fuse boxes were commonplace.
But as our demands for power increased,
homeowners replaced the 60-amp boxes with larger,
without power for at least one to two days while the
project is in process.
Also check with your utility company to make
safer, and more reliable circuit breaker panels. Typical sure you know what equipment is theirs and what
new homes were built with perfectly adequate 100-amp belongs to you. In most cases, the electric meter and
load centers. But today, as average home size has risen everything on the street side belongs to the power
to more than 2,500 sq. ft. and the number of home company, and the meter base and everything on the
electronics has risen exponentially, 100 amps is often house side is yours. Be aware that if you tamper with
inadequate service. As a result, many homeowners have the sealed meter in any way, you likely will be fined.
upgraded to 200-amp service, and new single-family Utility companies will not re-energize your system
homes often include 250 amps or even 400 amp service. without approval from your inspecting agency.
Upgrading your electrical service panel from Upgrading a service panel is a major project.
100 amps to 200 amps is an ambitious project that Do not hesitate to call for help at any point if you’re
requires a lot of forethought. The first step is to obtain unsure what to do.
a permit. When you are ready to begin, you will need
to have your utility company disconnect your house
from electrical service at the transformer that feeds tools & Materials ▸
your house. When you schedule this, talk to your utility
company about the size of your service drop or lateral. 200-amp load center Weatherhead
That may need to be upgraded too. Not only does this (service panel) Service cable
involve working them into your schedule, it means you 200-amp bypass Circuit wires
will have no power during the project. You can rent a meter base Plywood backer board
portable generator to provide a circuit or two, or you can Circuit breakers Screwdrivers
run a couple extension cords from a friendly neighbor. (AFCI if required Drill/driver
But unless you are a very fast worker, plan on being by local code) Tape
Schedule 80 or Allen wrench
RmC conduit Circuit tester
and fittings multimeter
After
Before
Modern homeowners consume more power than our
forebears, and it is often necessary to upgrade the electrical
service to keep pace. While homeowners are not allowed to
make the final electrical service connections, removing the old
panel and installing the new panel and meter base yourself
can save you hundreds or even thousands of dollars.
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Service drop cables
Weatherhead
Service mast
RMC conduit Service
entrance
cables
Power meter
Power meter Meter base
Service
entrance
cables
Strap
Meter base
Conduit
Service lateral cables
Aboveground service drop . In this common configuration, Underground service lateral . Increasingly, homebuilders
the service cables from the closest transformer (called the are choosing to have power supplied to their new homes
service drop) connect to service entrance wires near the underground instead of an overhead service drop. running the
weatherhead. This connection is called the service point and is cables in the ground eliminates problems with power outages
where your property usually begins. The service entrance wires caused by ice accumulation or fallen trees, but it entails a
from the weatherhead are routed to a power meter that’s completely different set of cable and conduit requirements.
owned by your utility company but is housed in a base that’s For the homeowner, however, the differences are minimal,
considered your property. From the meter the service entrance because the hookups are identical once the power service
wires enter your house through the wall and are routed to the reaches the meter.
main service panel, where they are connected to the main
circuit breaker.
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locating Your New Panel ▸
A
local codes dictate where the main service
panel may be placed relative to other parts of
your home. although the codes vary (and always
take precedence), national codes stipulate that
B
a service panel (or any other distribution panel)
may not be located near flammable materials, in a
bathroom, clothes closet or other area designated D
for storage, above stairway steps, or directly above
a workbench or other permanent work station f
or appliance. The panel also can’t be located in C
a crawl space. If you are installing a new service
entry hookup, there are many regulations regarding
height of the service drop and the meter. Contact E
your local inspections office for specific regulations.
All the equipment you’ll need to upgrade your main panel
is sold at most larger building centers. It includes (a) a new
200‑amp panel; (B) a 200‑amp bypass meter base (also called
a socket); (C) individual circuit breakers (if your new panel is
the same brand as your old one you may be able to reuse
the old breakers); (D) new, THW, THHW, THWN‑2. RHW, RHW‑2,
XHHW (2/0 copper seen here); (E) 2" dia. rigid metallic conduit;
(F) weatherhead shroud for mast.
Minimum
78” high
unobstructed
access
Maximum Meter
circuit breaker
height 79” (ideal
height 60”)
Shutoff switch
Minimum 36" deep
unobstructed
access Minimum 30" wide The main circuit breaker (called the service equipment)
unobstructed may need to be located outside next to the electric meter
access
if your main panel is too far away from the point where the
Attach to studs or to 3⁄ 4" service cable enters your house. The maximum distance
plywood backer allowed varies widely, from as little as 3 ft. to more than 10
ft. Wiring the service cable through the shutoff has the effect
of transforming your main panel into a subpanel, which will
impact how the neutral and ground wires are attached (see
Subpanels, pages 64 to 65).
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■ How to Replace a Main Panel
1 2
Shut off power to the house at the transformer . This Label all incoming circuit wires before disconnecting them.
must be done by a technician who is certified by your utility labels should be written clearly on tape that is attached to the
company. also have the utility worker remove the old meter cables outside of the existing service panel. Test the circuits
from the base. It is against the law for a homeowner to break before starting to make sure they are labeled correctly.
the seal on the meter.
3 4
Disconnect incoming circuit wires from breakers, Unscrew the lugs securing the service entry cables at the
grounding bar, and neutral bus bar. also disconnect cable top of the panel. For 240-volt service you will find two heavy-
clamps at the knockouts on the panel box. retract all circuit gauge SE cables, probably with black sheathing. Each cable
wires from the service panel and coil it up neatly, with the carries 120 volts of electricity. a neutral service cable, usually
labels clearly visible. of smaller gauge than the SE cables, will be attached to the
neutral bus bar. This cable returns current to the source.
(continued)
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5 6
Remove the old service panel box . Boxes are rated for Replace the old panel backer board with a larger board
a maximum current capacity; and if you are upgrading, the in the installation area (see sidebar, page 52). a piece of 3⁄4"
components in the old box will be undersized for the new plywood is typical. Make sure the board is well secured at wall
service levels. The new box will have a greater number of framing members.
circuit slots as well.
7 8
Attach the new service panel box to the backer board, Attach properly sized cable clamps to the box at the
making sure that at least two screws are driven through the knockout holes. Install one cable per knockout in this type of
backer and into wall studs. Drill clearance holes in the back of installation and plan carefully to avoid removing knockouts that
the box at stud locations if necessary. Use roundhead screws you do not need to remove (if you do make a mistake, you can
that do not have tapered shanks so the screwhead seats flat fill the knockout hole with a plug).
against the panel.
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Splicing in the Box ▸ 9
Some wiring codes allow you to make splices inside the
panel box if the circuit wire is too short. Use the correct
wire cap and wind electrical tape over the conductors
where they enter the cap. If your municipality does
not allow splices in the panel box, you’ll have to rectify
a short cable by splicing it in a junction box before it
reaches the panel and then replacing the cable with a
longer section for the end of the run. Make sure each
circuit line has at least 12" of slack.
Attach the white neutral from each circuit cable to the
neutral bus bar. Most panels have a preinstalled neutral bus
bar, but in some cases you may need to purchase the bar
separately and attach it to the panel back. The panel should
also have a separate grounding bar that you also may need to
purchase separately. attach the grounds as well.
10 11
Attach the hot lead wire to the terminal on the circuit Create an accurate circuit index and affix it to the inside
breaker, and then snap the breaker into an empty slot. When of the service panel door. list all loads that are on the circuit
loading slots, start at the top of the panel and work your way as well as the amperage. Once you have restored power to the
downward. It is important that you balance the circuits as you new service panel (see step 18), test out each circuit to make
go to equalize the amperage. For example, do not install all the sure you don’t have any surprises. With the main breakers on,
15-amp circuits on one side and all the 20-amp circuits on shut off all individual circuit breakers, and then flip each one
the other. on by itself. Walk through your house and test every switch and
receptacle to confirm the loads on that circuit.
(continued)
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12 13
Install grounding conductors (see pages 58 to 59). local Replace the old meter base (have the utility company
codes are very specific about how the grounding and bonding remove the meter when they shut off power to the house, step
needs to be accomplished. For example, some require 1). remove the old meter base, also called a socket, and install
multiple rods driven at least 6 ft. apart. Discuss your grounding a new base that’s rated for the amperage of your new power
requirements thoroughly with your inspector or an electrician service. Here, a 200-amp bypass meter base is being installed.
before making your plan.
14 15
Update the conduit that runs from your house to the Install new service entrance wires . Each wire carries
bottom of the meter base. This should be 2" rigid conduit 120 volts from the meter to the service wire lugs at the top
in good repair. attach the conduit to the base and wall with of your service panel. Code is very specific about how these
the correct fittings. rigid metal conduit is a good option, but connections are made. In most cases, you’ll need to tighten
Schedule 80 PVC is probably the best choice for housing the the terminal nuts with a specific amount of torque that
service entrance wires. requires a torque wrench to measure. also attach the sheathed
neutral wire to the neutral/grounding lug.
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16 17
Attach the SE wires to the lugs connected to the main Install service entrance wires from the meter to the
breakers at the top of your service entry panel. Do not remove weatherhead, where the connections to the service drop wires
too much insulation on the wires—leaving the wires exposed are made. Only an agent for your public utility company may
is a safety hazard. The neutral service entry wire is attached make the hookup at the weatherhead.
either directly to the neutral bus bar or to a metal bridge that
is connected to the neutral bonding bus bar. Install the green
grounding screw provided with the panel.
tall Mast, Short Roof ▸ 18
The service drop must occur at least 10 ft. above
ground level, and as much as 14 ft. in some cases.
Occasionally, this means that you must run the
conduit for the service mast up through the eave of
your roof and seal the roof penetration with a boot.
Weatherhead
Service drop
Mast (conduit)
Boot minimum
18 inches from
the bottom of the
drip loop
Have the panel and all connections inspected and
approved by your local building department, and then contact
the public utility company to make the connections at the
power drop. Once the connections are made, turn the main
breakers on and test all circuits.
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Grounding & Bonding a Wiring System
A ll home electrical systems must be bonded and
grounded according to code standards. This
entails two tasks: the metal water and gas pipes must
be connected electrically to create a continuous low
resistance path back to the main electrical panel;
and the main electrical panel must be grounded to
a grounding electrode such as a ground rod or rods
driven into the earth near the foundation of your
house. Although the piping system is bonded to the
ground through your main electrical service panel, the
panel grounding and the piping bonding are unrelated
when it comes to function. The grounding wire that
runs from your electrical panel to grounding electrode
helps even out voltage increases that often occur
because of lightning and other causes. The wires that
bond your metal piping are preventative, and they
only become important in the unlikely event that an
electrical conductor energizes the pipe. In that case,
correct bonding of the piping system will ensure that
the current does not remain in the system, where it
could electrocute anyone who touches a part of the
system, such as a faucet handle. Bonding is done
relatively efficiently at the water heater, as the gas
piping and water piping generally there.
gas pipe in older homes is usually steel or copper.
The bonding connection point for these pipes can be
at any accessible location, such as at the water heater
or at the gas meter. gas pipe in some new homes is
a flexible material called corrugated stainless steel
tubing (CSST). The bonding point for CSST must be
at the first piece of steel or copper pipe where the gas
service enters the home. This is because lightning can
blow holes in CSST, causing a gas leak.
tools & Materials ▸
Hammer 3 pipe
Straight edge ground clamps
screwdriver Eye and ear
Drill protection
½" drill bit Work gloves
A length of grounding rods
ground wire 5-lb. maul A pair of 8-ft .-long metal ground rods are driven into the
Some wire staples Caulk earth next to your house to provide a path to ground for your
home wiring system.
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■ How to Bond Metallic Piping
1 2
Determine the amperage rating of your electrical service Run the bonding wire from a point near your water heater
by looking at your main breakers. The system amperage (a convenient spot if you have a gas-fueled water heater) to
(usually 100 or 200 amps) determines the required gauge an exit point where the wire can be bonded to the grounding
of the bonding wire you need. #4 copper wire is sufficient wire that leads to the exterior grounding electrodes. This is
for service not exceeding 200 amps. Smaller, less expensive frequently done at the service panel. run this wire as you
copper wire is allowed for services between 100 and 175 would any other cable, leaving approximately 6 to 8 ft. of wire
amps. Check with your electrical inspector if you want to use at the water heater. If you are running this wire through the
wire smaller than #4. ceiling joists, drill a 1⁄2" hole as close to the center as possible
to not weaken the joist. Staple the wire every 2 ft. if running it
parallel to the joists.
3 4
Install pipe ground clamps on each pipe (hot water supply, Route the ground wire through each clamp wire hole and
cold water supply, gas), roughly a foot above the water heater. then tighten the clamps onto the wire. Do not cut or splice the
Do not install clamps near a union or elbow because the wire: The same wire should run through all clamps.
tightening of the clamps could break or weaken soldered
joints. also make sure the pipes are free and clear of any paint,
rust, or any other contaminant that may inhibit a good clean
connection. Do not overtighten the clamps. Use clamps that
are compatible with the pipe so that corrosion will not occur.
Use copper or brass clamps on copper pipe. Use brass or steel
clamps on steel pipe. (continued)
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5 6
At the panel, turn off the main breaker. Open the cover Locate an open hole on your ground and neutral bus
by removing the screws, and set the cover aside. route the and insert the ground wire. These holes are large enough to
ground wire through a small 3⁄8" hole provided towards the accommodate up to a #4 awg wire, but it may be difficult at
rear of the panel on the top or bottom. You will usually have times. If you’re having trouble pushing the wire in, trim a little
to knock the plug out of this hole by placing a screwdriver on wire off the end and try with a clean cut piece. Secure the set
it from the outside and tapping with a hammer. Make sure screw at the lug. replace the panel cover and turn the main
the ground wire will not come into contact with the bus bars breaker back on.
in the middle of the panel or any of the load terminals on the
breakers.
■ Tips for Grounding the Main Service Panel
Neutral bus
Grounding bus
The neutral and grounding wires should not be connected Metallic conduit must be physically and electrically connected
to the same bus in most subpanels. The grounding bus should to panel cabinets. a bonding bushing may be required in some
be bonded to the subpanel cabinet. The neutral bus should not cases, where not all of a knockout is removed.
be bonded to the subpanel cabinet.
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■ Ground Rod Installation
The ground rod is an essential part of the grounding
system. Its primary function is to create a path to Exercise Your Breakers ▸
ground for electrical current, such as lightning, line
Your breakers (including the main) should be
surges, and unintentional contact with high voltage
“exercised” once a year to ensure proper mechanical
lines. If you upgrade your electrical service you likely
function. Simply turn them off and then back on. a
will need to upgrade your grounding wire and rods to
convenient time to perform the exercise is at daylight
meet code.
savings time, when you’ll need to reset all of your
Note: Different municipalities have different
clocks anyway.
requirements for grounding, so be sure to check with
the AHJ (Authority Having Jurisdiction) first before
attempting to do this yourself.
Call before you dig! make sure the area where you
will be installing the ground rods is free and clear from
any underground utilities.
■ How to Install a Grounding Electrode System
1 2
Begin by purchasing two copper-coated steel ground Drill a 5⁄16" hole in the rim joist of your house, as close as
rods 5/8" diameter by 8' long. Grounding rods have a driving practical to the main service panel to the outside of the house
point on one end and a striking face on the other end. above the ground level at least 6".
(continued)
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3 4
About a foot from the foundation of the house, pound Run uninsulated #4 copper wire from the ground bus in
one ground rod into the earth with a five-pound maul. If you your main service panel through the hole in the rim joist and to
encounter a rock or other obstruction, you can pound the the exterior of the house, leaving enough wire to connect the
ground rod at an angle as long as it does not exceed 45°. Drive two ground rods together.
until only 3" or 4" of the rod is above ground. Measure at least
6 ft. from the first ground rod and pound in another one.
5 6
Using a brass clamp commonly referred to as an acorn, Connect the second ground rod with another acorn to the
connect the wire to the first ground rod, pulling the wire taut uncut grounding wire previously pulled through the first acorn.
so no slack exists. Continue pulling the wire to reach the Trim the excess wire.
second grounding rod, creating a continuous connection.
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7 8
Dig out a few inches around each rod to create clearance Inject caulk into the hole in the rim joist on both the interior
for the five-pound maul. Creating a shallow trench beneath and exterior side.
the grounding wire between the rods is also a good idea. Drive
each rod with the maul until the top of the rod is a few inches
below grade.
■ Tips for Grounding
Grounding electrode
A listed metal strap may be used to ground indoor A piece of reinforcing bar encased in a concrete footing is a
communication wires such as telephone and cable TV if an common grounding electrode in new construction. Called an
intersystem bonding terminal is not available. ufer, the electrode must be No. 4 or larger rebar and at least 20 ft.
long. (Shown prior to pouring concrete.)
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Installing a Subpanel
I nstall circuit breaker subpanels if the main circuit
breaker panel does not have enough open breaker slots
for the new circuits you are planning. Subpanels serve as
(or three double‑pole breakers), while the largest
models can hold 20 single‑pole breakers or more.
Subpanels often are mounted near the main
a second distribution center for connecting circuits. They circuit breaker panel. Or, for convenience, they can
receive power from a double‑pole circuit breaker you be installed close to the areas they serve, such as in
install in the main circuit breaker panel. a new room addition or a garage. In a finished room,
If the main service panel is so full that there is no a subpanel can be painted or housed in a decorative
room for the double‑pole subpanel breaker, you can cabinet so it is less of a visual distraction. If it is
reconnect some of the existing 120‑volt circuits to covered, make sure the subpanel is easily accessible
special slimline breakers (photos below). and clearly identified.
Plan your subpanel installation carefully, making
sure your electrical service supplies enough power to
support the extra load of the new subpanel circuits.
Assuming your main service is adequate, consider Tools & Materials ▸
installing an oversized subpanel breaker in the main
panel to provide enough extra amps to meet the needs Hammer Cable clamps
of future wiring projects. Screwdriver Three‑wire NM cable
Also consider the physical size of the subpanel, Circuit tester Cable staples
and choose one that has enough extra slots to hold Cable ripper Double‑pole circuit breaker
circuits you may want to install later. The smallest Combination tool Circuit breaker subpanel
panels have room for up to six single‑pole breakers Screws Slimline circuit breakers
Slimline
breakers
Single‑pole replace
circuit single‑pole
breakers breakers
Before After
To conserve space in a service panel, you can replace single-pole breakers with slimline breakers. Slimline breakers take up
half the space of standard breakers, allowing you to fit two circuits into one single slot on the service panel. In the service panel
shown above, four single-pole 120-volt breakers were replaced with slimline breakers to provide the double opening needed for a
30-amp, 240-volt subpanel feeder breaker. Use slimline breakers (if your municipality allows them) with the same amp rating as the
standard single-pole breakers you are removing, and make sure they are approved for use in your panel. If your municipality and
panel allow slimline breakers, there may be restrictions on the quantity and location where they may be installed on the panel.
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Text Page: 64
Main dwelling Detached dwelling
Hot
Hot
Neutral bus
Ground
Grounding bus
Neutral bus Grounding bus
Jumpers
Neutral
Electrode Electrode
Wiring diagram for wiring a feeder from the main service panel to a subpanel in a separate building.Illo 280 CG_Codes 06-15-2009 ■ How to Install a Subpanel 1 2 1 ⁄2 ” 3
Subpanels are subject to the same Open a knockout in the subpanel Attach a cable clamp to the knockout
installation and clearance rules as service using a screwdriver and hammer. Run in the subpanel. Insert the cable into the
panels. The subpanel can be mounted to the feeder cable from the main circuit subpanel, and then anchor it to framing
the sides of studs or to plywood attached breaker panel to the subpanel, leaving members within 8" of each panel and
between two studs. The panel shown about 2 ft. of excess cable at each end. every 54" thereafter.
here extends 1⁄2" past the face of studs
so it will be flush with the finished wall
surface.
(continued)
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4 5 Main lug 6
Lug
Hot bus bars
Neutral
bus bar
Grounding Lug
bus bar
Strip away outer sheathing from the Strip 1⁄2" of insulation from the white Strip away 1⁄2" of insulation from the
feeder cable using a cable ripper. Leave neutral feeder wire, and attach it to the red and the black feeder wires. Attach
at least 1⁄4" of sheathing extending into main lug on the subpanel neutral bus one wire to the main lug on each of the
the subpanel. Tighten the cable clamp bar. Connect the grounding wire to a hot bus bars. Fold excess wire around
screws so the cable is held securely, but setscrew terminal on the grounding bus the inside edge of the subpanel.
not so tightly that the wire sheathing bar. Fold excess wire around the inside
is crushed. edge of the subpanel.
7 8
Slimline
breakers
At the main circuit breaker panel, shut off the main Strip away the outer sheathing from the feeder cable so
circuit breaker, and then remove the coverplate and test for that at least 1⁄4" of sheathing will reach into the main service
power. If necessary, make room for the double-pole feeder panel. Attach a cable clamp to the cable, and then insert the
breaker by removing single-pole breakers and reconnecting cable into the knockout, and anchor it by threading a locknut
the wires to slimline circuit breakers. Open a knockout for the onto the clamp. Tighten the locknut by driving a screwdriver
feeder cable using a hammer and screwdriver. Note: some against the lugs. Tighten the clamp screws so the cable is held
panels do not allow slimline breakers and some restrict where securely, but not so tightly that the cable sheathing is crushed.
slimline breakers can be installed. Read the instructions on the
panel cover.
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9 10
Grounding bus bar
Neutral bus bar
Bend the bare copper wire from the feeder cable around Strip away 1⁄2" of insulation from the white feeder wire.
the inside edge of the main circuit breaker panel, and connect Attach the wire to one of the setscrew terminals on the
it to one of the setscrew terminals on the grounding bus bar. neutral bus bar. Fold excess wire around the inside edge of the
service panel.
11 12 13
Guide hook pivot
Strip 1⁄2" of insulation from the red Hook the end of the feeder circuit If necessary, open two tabs where
and the black feeder wires. Attach one breaker over the guide hooks on the the double-pole feeder breaker will
wire to each of the setscrew terminals panel, and then push the other end fit, and then reattach the cover plate.
on the double-pole feeder breaker. forward until the breaker snaps onto Label the feeder breaker on the circuit
Note: If your subpanel arrived with a the hot bus bars (follow manufacturer’s index. Turn the main breaker on, but
preinstalled grounding screw in the directions). Fold excess wire around the leave the feeder breaker off until all
panel back, remove and discard it. inside edge of the circuit breaker panel. subpanel circuits have been connected
and inspected.
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age: 66 Text Page: 67
Baseboard Heaters
B aseboard heaters are a popular way to provide
additional heating for an existing room or primary
heat to a converted attic or basement.
Tools & Materials ▸
Heaters are generally wired on a dedicated Drill/driver
240‑volt circuit controlled by a thermostat. Several Wire stripper
heaters can be wired in parallel and controlled by a Cable ripper
single thermostat (see circuit map 15, page 39). Wallboard saw
Baseboard heaters are generally surface‑mounted Baseboard heater or heaters
without boxes, so in a remodeling situation, you only 240‑thermostat (in‑heater or in‑wall)
need to run cables before installing wallboard. Be sure 12/2 NM cable
to mark cable locations on the floor before installing Electrical tape
drywall. Retrofit installations are also not difficult. Basic wiring supplies
You can remove existing baseboard and run new cable
in the space behind. Baseboard heaters (and other
heating equipment) get very hot and can ignite nearby
combustible materials. Maintain the manufacturers
recommended distance between the heater and
materials such as curtains, blinds, and wood.
Baseboard heaters can provide primary or supplemental heat for existing rooms or additions. Install heaters with clear space
between the heater and the floor.
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■ Baseboard Thermostats
In‑heater Wall‑mount
Single‑pole Double‑pole thermostat thermostat
thermostat thermostat
Single‑pole and double‑pole thermostats work in a similar In‑heater and wall‑mount are the two types of baseboard
manner, but double-pole models are safer. The single-pole thermostats you can choose from. If you are installing multiple
model will open the circuit (causing shutoff) in only one leg of heaters, a single wall-mount thermostat is more convenient.
the power service. Double-pole models have two sets of wires Individual in-heater thermostats give you more zone control,
to open both legs, lessening the chance that a person servicing which can result in energy savings.
the heater will contact a live wire.
How Much Heater Do You Need? ▸
If you don’t mind doing a little math, determining how 7. Add 20% if the space above is not well insulated:
many lineal feet of baseboard heater a room requires is
not hard. 8. Add 10% if ceiling is more than 8 ft. high:
9. Total of the baseline wattage plus all additions:
1. Measure the area of the room in square feet
(length × width): 10. Divide this number by 250 (the wattage produced per
2. Multiply the area by 10 to get the baseline minimum foot of standard baseboard heater):
wattage: 11. Round up to a whole number. This is the minimum
3. Add 5% for each newer window or 10% for each number of feet of heater you need.
older window:
4. Add 10% for each exterior wall in the room: Note: It is much better to have more feet of heater than is
5. Add 10% for each exterior door: required than fewer. Having more footage of heater does
6. Add 10% if the space below is not insulated: not consume more energy; it does allow the heaters to
work more efficiently.
Planning Tips for Baseboard Heaters ▸
• Baseboard heaters require a dedicated circuit. A • Do not mount heaters directly on the floor. You
20-amp, 240-volt circuit of 12-gauge copper wire will should maintain at least 1" of clear space between
power up to 16 ft. of heater. the baseboard heater and the floor covering.
• Do not install a heater beneath a wall receptacle. • Installing heaters directly beneath windows is a
Cords hanging down from the receptacle are a good practice.
fire hazard. • Locate wall thermostats on interior walls only, and do
not install directly above a heat source.
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■ How to Install a 240‑Volt Baseboard Heater
1 2
Clamp
screw
Wire
connection
box
At the heater locations, cut a small hole in the drywall 3" to Remove the cover on the wire connection box. Open a
4" above the floor. Pull 12/2 NM cables through the first hole: knockout for each cable that will enter the box, and then feed
one from the thermostat, the other to the next heater. Pull all the cables through the cable clamps and into the wire
the cables for subsequent heaters. Middle-of-run heaters will connection box. Attach the clamps to the wire connection
have two cables, while end-of-run heaters have only one cable. box, and tighten the clamp screws until the cables are
(See also circuit map 15, page 39.) gripped firmly.
3 4 To next heater
To element
From
thermostat
Grounding
screw
Anchor the heater against wall about 1" off floor by driving Make connections to the heating element if the power
flathead screws through the back of the housing and into wires are coming from a thermostat or another heater
studs. Strip away cable sheathing so at least 1⁄2" of sheathing controlled by a thermostat. See the next page for other wiring
extends into the heater. Strip 3⁄4" of insulation from each wire schemes. Connect the white circuit wires to one of the wire
using a combination tool. leads on the heater. Tag white wires with black tape to indicate
they are hot. Connect the black circuit wires to the other
wire lead. Connect a grounding pigtail to the green grounding
screw in the box, and then join all grounding wires with a wire
connector. Reattach the cover.
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Text Page: 70
One heater with end‑cap thermostat.
Run both power leads (black plus tagged
neutral) into the connection box at either
end of the heater. If installing a single-pole
thermostat, connect one power lead to
one thermostat wire and connect the
other thermostat wire, to one of the
heater leads. Connect the other hot
LINE wire to the other heater lead. If you
are installing a double-pole thermostat,
make connections with both legs of the
power supply.
Multiple heaters. At the first heater,
join both hot wires from the thermostat
to the wires leading to the second heater
in line. Be sure to tag all white neutrals
hot. Twist copper ground wires together
and pigtail them to the grounding screw
in the baseboard heater junction box.
This parallel wiring configuration ensures
that power flow will not be interrupted to
the downstream heaters if an upstream
heater fails.
Wall‑mounted thermostat. If installing a
wall-mounted thermostat, the power leads
should enter the thermostat first and then
be wired to the individual heaters singly or
in series. Hookups at the heater are made
as shown in step 4. Be sure to tag the
white neutral as hot in the thermostat box
as well as in the heater box.
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age: 70 Text Page: 71
Wall Heaters
I nstalling a wall heater is an easy way to provide
supplemental heat to a converted attic or basement
without expanding an existing HVAC system.
Wall heaters are easy to install during a remodel
(most have a separate can assembly that you attach to
the framing before the drywall is installed). They can
also be retrofitted.
Most models available at home centers use
120‑volt current (shown below), but 240‑volt models
are also available.
Tools & Materials ▸
Drywall saw Wire connectors
Drill Wall heater
Fish tape Thermostat
Combination tool (optional)
Screwdrivers Wallboard saw Wall heaters are an easy-to-install way to provide
12/2 NM cable supplemental heat. Some models have built-in thermostats,
while others can be controlled by a remote thermostat.
■ How to Install a Wall Heater in a Finished Wall
1 2
Make an opening in the wall for the heater. Use a stud Turn power off, and test for power. Pull 12/2 NM cable
finder to locate a stud in the area where you want to install from the main panel to the wall opening. If the heater
the heater. Mark the opening for the heater according to the is controlled by a separate thermostat, pull cable to the
manufacturer’s guidelines so that one side of the heater sits thermostat, and then run another cable from the thermostat to
flush with a stud. Pay attention to clearance requirements. Cut the heater location.
the opening with a wallboard saw. If the wall is open, install the
heater can before hanging drywall (inset).
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3 4 5
Disconnect and remove the motor Install the can in the opening. Wire the heater. Connect the black
unit from the heater can. Remove a Secure the cable with a clamp, leaving circuit wire to one of the black heater
knockout from the can, and route the 8" to 12" of cable exposed. Attach leads. Connect the white circuit wire to
cable into the can. the can to the framing as directed by the other lead. Connect the grounds.
the manufacturer.
6
Secure the heater unit in the can Variation: Connect a thermostat to control a wall heater. Some wall heaters do not
as directed by the manufacturer. use built-in thermostats. Install a thermostat in the heater circuit before the wall
Reconnect the motor if necessary. heater. Connect the black and the white wires coming from the main panel to the red
Attach the grill and thermostat knob leads on the thermostat. Connect the wires going to the heater to the black leads on
as directed. Connect the new circuit the thermostat. Connect the grounds.
breaker at the main panel.
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Backup Power Supply
I nstalling a backup generator is an invaluable way to
prepare your family for emergencies. The simplest
backup power system is a portable gas‑powered
can’t easily be run with an extension cord. But perhaps
the most important job a transfer switch performs is
to disconnect the utility power. If the inactive utility
generator and an extension cord or two. A big benefit power line is attached to the service panel, “backfeed”
of this approach is that you can run a refrigerator of power from your generator to the utility line can
and a few worklights during a power outage with a occur when the generator kicks in. This condition
tool that can also be transported to remote job sites could be fatal to line workers who are trying to
or on camping trips when it’s not doing emergency restore power. The potential for backfeed is the main
backup duty. This is also the least expensive way to reason many municipalities insist that only a licensed
provide some backup power for your home. You can electrician hook up a transfer switch. Using a transfer
purchase a generator at most home centers and be switch not installed by a professional may also void the
up and running in a matter of hours. If you take this warranty of the switch and the generator.
approach, it is critically important that you make Automatic transfer switches turn on the generator
certain any loads being run by your generator are and switch off the utility supply when they detect a
disconnected from the utility power source. significant drop in line voltage. They may be installed
The next step up is to incorporate a manual with portable generators, provided the generator is
transfer switch for your portable generator. Transfer equipped with an electric starter.
switches are permanently hardwired to your service Large standby generators that resemble central air
panel. They are mounted on either the interior or conditioners are the top of the line in backup power
the exterior of your house between the generator supply systems. Often fueled by home natural gas
and the service panel. You provide a power feed from lines or propane tanks that offer a bottomless fuel
the generator into the switch. The switch is wired to source, standby generators are made in sizes with as
selected essential circuits in your house, allowing you much as 20 to 40 kilowatts of output—enough to
to power lights, furnace blowers, and other loads that supply all of the power needs of a 5,000‑sq.‑ft. home.
Generators have a range of uses.
Large hard-wired models can provide
instant emergency power for a whole
house. Smaller models (below) are
convenient for occasional short-term
backup as well as job sites or
camping trips.
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■ Options for Backup Generators
A 2,000‑ to 5,000‑watt gas‑powered generator and a A permanent transfer switch patches electricity from
few extension cords can power lamps and an appliance or a large portable generator through to selected household
two during shorter-term power outages. Appliances must circuits via an inlet at your service panel (inset), allowing you to
not be connected to household wiring and the generator power hardwired fixtures and appliances with the generator.
simultaneously. Never plug a generator into an outlet. Never
operate a generator indoors. Run extension cords through a
garage door.
For full, on‑demand backup service, install a large standby generator wired through to an automatic transfer panel. In the
event of a power outage, the household system instantly switches to the generator.
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■ A Typical Backup System
Portable backup
generator
Service entry cables
Main
panel
Inlet
box
Manual
transfer
switch
Backup generators supply power to a manual transfer switch, which disconnects the house from the main service wires and
routes power from the generator through selected household circuits.
■ Choosing a Generator
Choosing a generator for your home’s needs requires 10,000 watts). If the surge watts aren’t listed, ask,
a few calculations. The chart below gives an estimate or check the manual. Some generators can’t develop
of the size of generator typically recommended for a many more surge watts than run watts; others can
house of a certain size. You can get a more accurate produce twice as much surge as run wattage.
number by adding up the power consumption (the It’s not necessary to buy a generator large enough to
watts) of all the circuits or devices to be powered by match the surge potential of all your circuits (you won’t
a generator. It’s also important to keep in mind that, be turning everything on simultaneously), but surge
for most electrical appliances, the amount of power watts should factor in your purchasing decision. If you
required at the moment you flip the ON switch is will be operating the generator at or near capacity, it is
greater than the number of watts required to keep also a wise practice to stagger startups for appliances.
the device running. For instance, though an air
conditioner may run on 15,000 watts of power, it will
require a surge of 30,000 watts at startup (the power SIzE oF HouSE rECoMMENDED GENErATor
range required to operate an appliance is usually listed (IN SquArE FEET) SIzE (IN kILoWATTS)
somewhere on the device itself). These two numbers
Up to 2,700 5–11
are called run watts and surge watts. Generators are
2,701–3,700 14–16
typically sold according to run watts (a 5,000‑watt
generator can sustain 5,000 watts). They are also rated 3,701–4,700 20
for a certain number of surge watts (a 5,000‑watt 4,701–7,000 42–47
generator may be able to produce a surge of
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■ Types of Transfer Switches
Cord‑connected transfer switches (shown above) are When using a cord‑connected switch, consider mounting
hard-wired to the service panel (in some cases they’re installed an inlet box to the exterior wall. This will allow you to connect
after the service panel and operate only selected circuits). a generator without running a cord into the house.
These switches contain a male receptacle for a power supply
cord connected to the generator. Automatic transfer switches
(not shown) detect voltage drop-off in the main power line and
switch over to the emergency power source.
Generator Tips ▸
If you’ll need to run sensitive electronics such A generator that will output 240‑volt service is
as computers or home theater equipment, look for a required to run most central air conditioners. If your
generator with power inverter technology that dispenses generator has variable output (120/240) make sure the
“clean power” with a stable sine wave pattern. switch is set to the correct output voltage.
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■ Running & Maintaining a Backup System
Even with a fully automatic standby generator
system fueled by natural gas or propane, you will
need to conduct some regular maintenance and
testing to make sure all systems are ready in the
event of power loss. If you’re depending on a
portable generator and extension cords or a standby
generator with a manual transfer switch, you’ll also
need to know the correct sequence of steps to follow
in a power emergency. Switches and panels also need
to be tested on a regular basis, as directed in your
owner’s manual. And be sure that all switches (both Pull‑cord starter
interior and exterior) are housed in an approved Smaller portable generators often use pull-cords instead of
enclosure box. electric starters.
ANAToMY oF A PorTABLE BACkuP GENErATor
Fuel tank
Built‑in GFCI
Voltage
selector
Built‑in circuit
breaker
AC power
outlets
Start switch
Gasoline engine
oil dipstick
Portable generators use small gasoline engines to generate power. A built-in electronics panel sets current to AC or DC and
the correct voltage. Most models will also include a built-in circuit breaker to protect the generator from damage in the event it
is connected to too many loads. Better models include features like built-in GFCI protection. Larger portable generators may also
feature electric starter motors and batteries for push-button starts.
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■ Operating a Manual System During an Outage
Plug the generator in at the inlet Start the generator with the pull-cord Flip the manual transfer switch.
box. Make sure the other end of the or electric starter (if your generator Begin turning on loads one at a time by
generator’s outlet cord is plugged into has one). Let the generator run for flipping breakers on, starting with the
the appropriate outlet on the generator several minutes before flipping the ones that power essential equipment.
(120-volt or 120/240-volt AC) and the transfer switch. Do not overload the generator or the
generator is switched to the appropriate switch, and do not run the generator
voltage setting. at or near full capacity for more than
30 minutes at a time.
■ Maintaining & Operating an Automatic Standby Generator
If you choose to spend the money and install a dedicated standby generator of 10,000 watts or more and operate it through
an automatic transfer switch or panel, you won’t need to lift a hand when your utility power goes out. The system kicks in by
itself. However, you should follow the manufacturer’s instructions for testing the system, changing the oil, and running the
motor periodically.
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Installing a Transfer Switch
A transfer switch is installed next to the main
service panel to override the normal electrical
service with power from a backup generator during
a power outage. Manual transfer switches require an
operator to change the power source, while automatic
switches detect the loss of power, start the back‑up
generator, and switch over to the backup power feed.
Because the amount of electricity created by a backup
generator is not adequate to power all of the electrical
circuits in your house, you’ll need to designate a few
selected circuits to get backup current (see page 81).
Tools & Materials ▸
Circuit tester Level A manual transfer switch connects emergency circuits in
Drill/driver Manual transfer switch your main panel to a standby generator.
Screwdrivers Screws
Hammer Wire connectors
Wire cutters (yellow)
Cable ripper Standby power
Wire strippers generator
One flip of a switch reassigns the power source for each critical circuit so your backup generator can keep your refrigerator,
freezer, and important lights running during an outage of utility power.
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Selecting Backup Circuits ▸
Before you purchase a backup generator, determine • Refrigerator: 750 watts
which loads you will want to power from your generator • Forced air furnace: 1,100 to 1,500 watts
in the event of a power loss. Generally you will want to • Incandescent lights: 60 watts per bulb (CFL and LED
power your refrigerator, freezer, and maybe a few lights. lights use less wattage)
Add up the running wattage ratings of the appliances • Sump pump: 800 to 1,000 watts
you will power up to determine how large your backup • Garage door opener: 550 to 1,100 watts
generator needs to be. Because the startup wattage of • Television: 300 watts
many appliances is higher than the running wattage,
avoid starting all circuits at the same time—it can Add the wattage values of all the loads you want to
cause an overload situation with your generator. Here power, and multiply the sum by 1.25. This will give you the
are some approximate running wattage guidelines (see minimum wattage your generator must produce. Portable
page 132 to 137 for more information on calculating standby generators typically output 5,000 to 7,500 watts.
electrical loads): Most larger, stationary generators can output 10,000 to
20,000 watts (10 to 20 kilowatts).
■ How to Install a Manual Transfer Switch
1 2
Turn off the main power breaker in your electrical service Determine which household circuits are critical for
panel. CAUTION: The terminals where power enters the main emergency usage during a power outage. Typically this will
breakers will still be energized. include the refrigerator, freezer, furnace, and at least one light
or small appliance circuit.
(continued)
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3 4
Match your critical circuits with circuit inlet on your pre- Select and remove a knockout at the bottom of the main
wired transfer switch. Try to balance the load as best you can service panel box. Make sure to choose a knockout that is
in the transfer switch: For example, if your refrigerator is on sized to match the connector on the flexible conduit coming
the leftmost switch circuit, connect your freezer to the circuit from the transfer switch.
farthest to the right. Double-pole (240-volt) circuits will require
two 120-volt circuit connections. Also make sure that 15-amp
and 20-amp circuits are not mismatched with one another.
5 6
Feed the wires from the transfer switch into the knockout Secure the flexible conduit from the switch box to the main
hole, taking care not to damage the insulation. You will note service panel using a locknut and a bushing where required.
that each wire is labeled according to which circuit in the
switch box it feeds.
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7 8
Attach the transfer switch box to the wall so the closer Remove the breaker for the first critical circuit from the
edge is about 18" away from the center of the main service main service panel box, and disconnect the hot wire lead from
panel. Use whichever connectors make sense for your the lug on the breaker.
wall type.
9 10
Locate the red wire for the switch box circuit that Locate the black wire from the same transfer switch circuit,
corresponds to the circuit you’ve disconnected. Attach the and twist it together with the old feed wire, using a yellow wire
red wire to the breaker you’ve just removed, and then reinstall connector. Tuck the wires neatly out of the way at the edges of
the breaker. the box. Proceed to the next circuit, and repeat the process.
(continued)
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11 12
If any of your critical circuits are 240‑volt circuits, attach Once you have made all circuit connections, attach the
the red leads from the two transfer switch circuits to the white neutral wire from the transfer switch to an opening in
double-pole breaker. The two circuits originating in the transfer the neutral bus bar of the main service panel.
switch should be next to one another, and their switches
should be connected with a handle tie. If you have no 240-volt
circuits you may remove the preattached handle tie and use
the circuits individually.
13 14
Attach the green ground wire from the transfer switch to Begin testing the transfer switch by making sure all of the
an open port on the grounding bar in your main service panel. switches on it are set to the LINE setting. The power should still
This should complete the installation of the transfer switch. be OFF at the main panel breakers.
Replace the cover on the service panel box, and make sure to
fill in the circuit map on your switch box.
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Standby Generators ▸
Make sure your standby generator is operating properly and has been installed professionally. See page 76 for
information on choosing a generator that is sized appropriately for your needs.
15 16
Before turning your generator on, attach the power cord Flip each circuit switch on the transfer switch box to GEN,
from the generator to the switch box. Never attach or detach a one at a time. Try to maintain balance by moving back and
generator cord with the generator running. Turn your standby forth from circuits on the left and right side. Do not turn all
power generator on, and let it run for a minute or two. circuits on at the same time. Observe the onboard wattage
meters as you engage each circuit, and try to keep the
wattage levels in balance. When you have completed testing
the switch, turn the switches back to LINE, and then shut off
your generator.
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outbuildings
N othing improves the convenience and usefulness
of an outbuilding more than electrifying it.
Running a new underground circuit from your house
light fixture and small appliances or power tools, a
120‑volt, 15‑amp circuit should be sufficient. A small
workshop may require one or two 120‑volt, 20‑amp
to an outbuilding lets you add receptacles and light circuits. If you need any 240‑volt circuits or more than
fixtures both inside the outbuilding and on its exterior. two 120‑volt, 20‑amp circuits, you will need to install
If you run power to an outbuilding, you are required to at least a 60‑amp subpanel with appropriate feeder
install at least one receptacle. wires. Installing a subpanel in an outbuilding is similar
Adding one or two 120‑volt circuits is not to installing one inside your home, but there are some
complicated, but every aspect of the project is strictly important differences.
governed by local building codes. Therefore, once You may use #14 copper wire for one 120‑volt,
you’ve mapped out the job and have a good idea of 15‑amp circuit or #12 copper wire for one 120‑volt,
what’s involved, visit your local building department to 20‑amp circuit. Use #10 copper wire for two 120‑volt,
discuss your plans and obtain a permit for the work. 20 amp circuits. Also, if the shed is more than 150
This project demonstrates standard techniques ft. away from the house, you may need heavier‑gauge
for running a circuit cable from the house exterior to a cable to account for voltage drop.
shed, plus the wiring and installation of devices inside Most importantly, don’t forget to call before you
the shed. To add a new breaker and make the final dig. Have all utility and service lines on your property
circuit connections to your home’s main service panel, marked even before you make serious project plans.
see page 52. If you run power to an outbuilding, you This is critical for your safety of course, and it may
are required to install at least one receptacle. affect where you can run the circuit cable.
First, determine how much current you will need.
For basic electrical needs, such as powering a standard
Adding an electrical circuit to an outbuilding such as this shed greatly expands the activities the building will support and
is also a great benefit for home security.
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Tools & Materials ▸
Spray paint Hacksaw Single‑pole switches (2) THNN wire
Trenching shovel 90° sweeps for Interior ceiling light (12 gauge)
(4" wide blade) conduit (2) fixture and metal 20‑amp GFCI‑
4" metal junction box Plastic conduit fixture box protected circuit
Metal L‑fittings (2) bushings (2) Exterior motion‑ breaker
and conduit nipple Pipe straps detector fixture and Wire stripper
for conduit Silicone caulk plastic fixture box Pliers
Wood screws and caulk gun EMT metal conduit Screwdrivers
Conduit with Double‑gang and fittings for Wire connectors
watertight boxes, metal (2) inside the shed Hand tamper
threaded and One exterior Utility knife Schedule 80 conduit
compression fittings receptacle box UF two‑wire cable Eye protection
Wrenches (with cover) (12 gauge)
Ceiling light
Security light
EMT conduit
Switches
rigid conduit from service box
L‑body
GFCI (covered)
Schedule 80 conduit EMT conduit
Schedule 80 conduit
uF cable
90° sweep 90° sweep
A basic outdoor circuit starts with a waterproof fitting at the house wall connected to a junction box inside. The underground
circuit cable—rated UF (underground feeder)—runs in a 24"-deep trench and is protected from exposure at both ends by metal or
PVC conduit. Inside the shed, standard NM cable runs through metal conduit to protect it from damage (not necessary if you will be
adding interior wallcoverings). All receptacles in the shed must be GFCI protected.
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■ How to Wire an Outbuilding
1 2
Identify the circuit’s exit point at the house and entry From outside, drill a hole through the exterior wall and the
point at the shed and mark them. Mark the path of the trench rim joist at the exit point for the cable (you’ll probably need to
between the exit and entry points using spray paint. Make the install a bit extender or an extra-long bit in your drill). Make the
route as direct as possible. Dig the trench to the depth required hole just large enough to accommodate the L-body conduit
by local code (24") using a narrow trenching shovel. fitting and conduit nipple.
3 4
Assemble the conduit and junction box fittings that From outside, seal the hole around the conduit with
will penetrate the wall. Here, we attached a 12" piece of 3⁄4" expandable spray foam or caulk, and then attach the free end
IMC (intermediate metallic conduit) and a sweep to a metal of the conduit to the back of a waterproof L-body fitting. Mount
junction box with a compression fitting and then inserted the the L-body fitting to the house exterior with the open end
conduit into the hole drilled in the rim joist. The junction box is facing downward.
attached to the floor joist.
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5 6
Cut a length of IMC to extend from the L-fitting down Inside the shed, drill a 3⁄4" dia. hole in the shed wall. On the
into the trench using a hacksaw. Deburr the cut edges of interior of the shed, mount a junction box with a knock-out
the conduit. Secure the conduit to the L-fitting, and then removed to allow the cable to enter through the hole. On the
attach a 90° sweep to the bottom end of the conduit using exterior side directly above the end of the UF trench, mount
compression fittings. Add a bushing to the end of the sweep to an exterior-rated receptacle box with cover. The plan (and your
protect the circuit cable. Anchor the conduit to the wall with a plan may differ) is to bring power into the shed through the
corrosion-resistant pipe strap. hole in the wall behind the exterior receptacle.
7 8
Run conduit from the exterior box down into the trench. Run UF cable from the house to the outbuilding. Feed one
Fasten the conduit to the building with a strap. Add a 90° end of the UF circuit cable up through the sweep and conduit
sweep and bushing, as before. Secure the conduit to the box and into the L-fitting at the house (the back or side of the fitting
with an offset fitting. Anchor the conduit with pipe straps, and is removable to facilitate cabling). Run the cable through the
seal the entry hole with caulk. wall and into the junction box, leaving at least 12" of extra
cable at the end.
(continued)
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9 10
Lay the UF cable into the trench, making sure it is not Inside the outbuilding, install the remaining boxes for the
twisted and will not contact any sharp objects. Roll out the cable, other switches, receptacles, and lights. With the exception of
and then feed the other end of the cable up through the conduit plastic receptacle boxes for exterior exposure, use metal boxes
and into the receptacle box in the shed, leaving 12" of slack. if you will be connecting the boxes with metal conduit.
11 12
Connect the electrical boxes with conduit and fittings. Cut a length of conduit to fit between the coupling and
Inside the outbuilding, you may use inexpensive EMT to the next box or fitting in the run. If necessary, drill holes for
connect receptacle, switch, and fixture boxes. Once you’ve the conduit through the centers of the wall studs. Attach the
planned your circuit routes, start by attaching couplings to all conduit to the fitting that you attached to the first box.
of the boxes.
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13 14
THNN wire
If you are surface‑mounting the conduit or running it Measure to find how much wire you’ll need for each
up or down next to wall studs, secure it with straps no more run, and cut pieces that are a foot or two longer. Before
than 3 ft. apart. Use elbow fittings for 90° turns and setscrew making L-turns with the conduit, feed the wire through the
couplings for joining straight lengths as needed. Make holes first conduit run.
through the wall studs only as large as necessary to feed the
conduit through.
15 16
Feed the other ends of the wires into the next box or Once you’ve reached the next box in line, coil the ends of
fitting in line. It is much easier to feed wire into 45° and 90° the wires and repeat the process with new wire for the next run.
elbows if they have not been attached to the conduit yet. Keep working until all of the wire is run and all of the conduit and
Continue feeding wire into the conduit and fitting until you fittings are installed and secured. If you are running multiple feed
have reached the next box in line. wires into a single box, write the origin or destination on a piece
of masking tape and stick it to each wire end.
(continued)
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17
Neutral wires
Hot wires
Grounding
wires
Box grounding
screw
Note: Your Code may require
an in-use
in‑use rated receptacle box Receptacle
receptacle
cover (see page 64).
box cover. grounding
screw
Make the wiring connections at the receptacles. Strip Variation: Installing a GFCI-protected breaker for the new
3
⁄4" of insulation from the circuit wires using a wire stripper. circuit at the main service panel is the best way to protect
Connect the white (neutral) wire and black (hot) wire of the UF the circuit and allows you to use regular receptacles in the
cable to the LINE screw terminals on the receptacle. Connect building, but an alternative that is allowed in many areas
the white (neutral) and black (hot) wires from the NM cable to is to run the service into a GFCI-protected receptacle and
the LOAD terminals. Pigtail the bare copper ground wires and then wire the other devices on the circuit in series. If you
connect them to the receptacle ground terminal and the metal use this approach, only the initial receptacle needs to be a
box. Install the receptacle and cover plate. GFCI receptacle.
18 19
Continue installing receptacles in the circuit run, and Install the light fixtures. For this shed, we installed a caged
then run service from the last receptacle to the switch box ceiling light inside the shed and a motion-detector security
for the light fixture or fixtures. (If you anticipate a lot of load light on the exterior side.
on the circuit, you should probably run a separate circuit
for the lights). Twist the white neutral leads and grounding
leads together and cap them. Attach the black wires to the
appropriate switches. Install the switches and cover plate.
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20 21
Run NM cable from the electrical box in the house at the At the service panel, feed the NM cable in through a cable
start of the new circuit to the main service panel. Use cable clamp. Arrange for your final electrical inspection before you
staples if you are running the cable in floor joist cavities. If the install the breaker. Then attach the wires to a new circuit
cable is mounted to the bottom of the floor joists or will be breaker, and install the breaker in an empty slot. Label the new
exposed, run it through conduit. circuit on the circuit map.
Turn on the new circuit, and test
22 all of the receptacles and fixtures.
Depress the Test button and then the
Reset button if you installed a GFCI
receptacle. If any of the fixtures or
receptacles is not getting power, check
the connections first, and then test the
receptacle or switch for continuity with
a multimeter. Backfill the trench.
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Standalone Solar Lighting System
A self‑contained electrical circuit with dedicated
loads, usually 12‑volt light fixtures, is one of
the most useful solar amenities you can install. A
and they produce direct current (DC) power. PV
solar panel systems can be small and designed to
accomplish a specific task, or they can be large
standalone system is not tied into your power grid, enough to provide power or supplementary power
which greatly reduces the danger of installing the to an entire house. Before you make the leap into a
components yourself. Plus, the fact that your light large system, it’s a good idea to familiarize yourself
fixtures are independent of the main power source with the mechanics of solar power. The small
means that even during a power outage you will have system demonstrated in this project is relatively
functioning emergency and security lights. simple and is a great first step into the world of
Installing a single solar‑powered circuit is relatively solar. The fact that the collector, battery, and lights
simple, but don’t take the dangers for granted. Your are a standalone system makes this a very easy
work will require permits and inspections in most project to accomplish. By contrast, installing panels
jurisdictions, and you can’t expect to pass if the work is that provide direct supplementary power through
not done to the exact specifications required. your main electrical service panel is a difficult
Solar panels that convert the sun’s energy into wiring job that should be done by professional
electricity are called photovoltaic (PV) panels, electricians only.
This 60‑watt solar panel is mounted on a garage roof and powers a self-contained home security lighting system. Not only does
this save energy costs, it keeps the security lights working even during power outages.
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■ Schematic Diagram for an Off‑the‑Grid Solar Lighting System
Load
Junction box
Photovoltaic panel (60 watt)
DC disconnect switch
override switch
Catastrophe fuse
Charge controller
12‑volt deep well
marine battery
Motion sensor (optional)
Tools & Materials ▸
Tape measure 20 ft. Unistrut 17⁄8" (2) 1⁄2" liquid 1
⁄2" Greenfield
Drill/driver with bits thick U‑channel (See tight connectors connectors
Caulk gun Resources, page 125) (2) Lay‑in (4) 11⁄16" junction boxes
Crimping tool (4) 45° Unistrut grounding lugs with covers
Wiring tools connectors (2) Insulated terminal (4) square boxes
Metal‑cutting saw (2) 90° Unistrut bars to accept one with covers
Photovoltaic panel angle brackets 2‑gauge wire and PVC 6"× 6" junction
(50 to 80 watts) (4) Unistrut hold 4 12‑gauge wires box with cover
Charge controller down clamps (2) Cord cap 14/2 UF wire
Catastrophe fuse (12) 3⁄8" spring nuts connectors for 1
⁄4" × 20 nuts and
Battery sized for (12) 3⁄8"‑dia. × 1"‑long 1
⁄2"‑dia. cable bolts with lock
3 day autonomy hex‑head bolts 1
⁄2" ground rod washers
Battery case with washers and clamp Roof flashing boot
Battery cables DC‑rated disconnect Copper wire Roof cement
12‑volt LED lights or double throw (6, 12‑gauge) Silicon caulk
including motion‑ snap switch Green ground screws Eye protection
sensor light 6" length of 1⁄2"‑dia. 1
⁄2" Flexible metallic
Additional 12‑volt light liquid‑tight flexible conduit or
fixtures as desired metallic conduit Greenfield
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■ Mounting PV Panels
The mounting stand for the PV panel is constructed from metal U-channel (a product called Unistrut is seen here. See
Resources page 125) and pre-bent fasteners. Position the solar panel where it will receive the greatest amount of sunlight for the
longest period of time each day—typically the south-facing side of a roof or wall. For a circuit with a battery reserve that powers
two to four 12-volt lights, a collection panel rated between 40 and 80 watts of output should suffice. These panels can range from
$200 to $600 in price, depending on the output and the overall quality.
The stand components are held Connections for the feed wires that An EPDM rubber boot seals off the
together with bolts and spring-loaded carry current from the collector are opening where the PVC conduit carrying
fasteners. The 45° and 90° connectors made inside an electrical box mounted the feed wires penetrates the roof.
are manufactured specifically for use on the back of the collector panel.
with this Unistrut system.
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■ How to Wire a DC Lighting Circuit
1 2
Mount a junction box inside the building where the conduit Plan the system layout. Determine the placement of the
and wiring enter from the power source. Secure the box to the battery, and then decide where you will position the charge
conduit with appropriate connectors. Run two #14 awg wires controller and DC disconnect. The battery should be placed at
through the conduit and connect them to the positive and least 18" off the floor, in a well-ventilated area where it won’t
negative terminals on the panel (see previous page). be agitated by everyday activity. Mark locations directly on
the wall.
3 4
Attach a junction box for enclosing the DC disconnect, Run flexible metal conduit from the entry point at the
which is a heavy-duty switch, to a wall stud near the battery power source to the junction box for the DC disconnect box.
and charge controller location. Use a metal single-gang box Use hangers rated for flexible conduit.
with mounting flanges.
(continued)
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5 6
Attach the DC disconnect switch to the wire leads from Attach a double gang metal junction box to the building’s
the power source. frame beneath the DC disconnect box to enclose the
charge controller.
7 8
Install the charge controller inside the box. Run flexible Mount a PVC junction box for the battery controller about 2
conduit with connectors and conductors from the disconnect ft. above the battery location, and install two insulated terminal
box and to the charge controller box. bars within the box.
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9 10
Build a support shelf for the battery using 2 × 4s. The shelf Set up grounding protection. Pound an 8-ft. long, 1⁄2"-dia.
should be at least 18" above ground. Set the battery on the ground rod into the ground outside the building, about 1 ft.
shelf in a sturdy plastic case. from the wall on the opposite side of the charge controller.
Leave about 2" of the rod sticking out of the ground. Attach a
ground rod clamp to the top of the rod. Drill a 5⁄16" hole through
the garage wall (underneath a shake or siding piece) and run
the #6-gauge THWN wire to the ground rod. This ground will
facilitate lightning protection. See pages 58 to 63 for more
information on grounding the system.
11 12
Wire the DC disconnect. Attach the two #14-gauge wires Wire the charge controller. Route two more #14-gauge
to the two terminals labeled “line” on the top of the DC wires from the bottom of the DC disconnect terminals into
disconnect switch. the 4" × 11⁄16" junction box and connect to the “Solar Panel
In” terminals on the charge controller. The black wire should
connect to the negative terminal in the PVC box and the red
to the positive lead on the charge controller. Finish wiring of
the charge controller according to the line diagram provided
with the type of controller purchased. Generally the load wires
connect to the orange lead, and the red wire gets tied to the
battery through a fuse.
(continued)
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13
OPTION: Attach a motion sensor. Some charge controllers Run wiring to the loads (exterior DC lighting fixtures in this
come equipped with a motion sensor to maximize the case) from the charge controller. DC light fixtures (12-volt) with
efficiency of your lighting system—these are especially LED bulbs can be purchased at marine and RV stores if you
effective when used with security lighting. The motion sensor can’t find them in your home center or electrical supply store.
is typically mounted to a bell box outside and wired directly
to the charge controller with an 18-gauge × 3-conductor
insulated cable. A system like this can support up to three
motion sensors. Follow the manufacturer’s directions for
installing and wiring the motion sensor.
14 15
Install the battery. Here, a deep-cell 12-volt marine battery is Install the catastrophe fuse onto the positive terminal
used. First, cut and strip each of the two battery cables at one using nuts and bolts provided with the battery cables. Connect
end and install into the battery control junction box through the battery cables to the battery while paying close attention
cord cap connectors. Terminate these wires on two separate, to the polarity (red to positive and black to negative). Make
firmly mounted insulated terminal blocks. sure all connections have been made and double checked.
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Troubleshooting & repairs
R unning new circuits and hooking up new fixtures
are fairly predictable projects when it comes
to estimating time and expense. This is less true
to deploy logical, systematic diagnostics. Educated
troubleshooting, you could say.
In this project you’ll learn how to use the most
with repairing problems in your system and fixtures. important diagnostic tool in any electrician’s toolkit:
In some cases, a repair is as simple as opening an the multimeter. These handy devices come in a
electrical box, spotting a loose wire connector and dizzying array of types and qualities, but for diagnostic
remaking the connection. But there are also times purposes they are used to take readings for current
when fixing a dead circuit or device is a highly (amperage), voltage and continuity (whether an
frustrating proposition. Such cases are almost always electrical path is open or closed). Once you learn the
caused by tricky diagnostic challenges. Wires are basics of operating a multimeter, you can enlist it in
hidden behind walls and there very often are no a logical, deductive manner to track down the source
visual clues to system breakdowns. So essentially, of a wiring problem. Once located, correcting the
minimizing repair frustration boils down to learning problem is usually very simple.
A
B
C
Diagnostic tools for home wiring use include: Touchless circuit tester (A) to safely check wires for current and confirm that
circuits are dead; Plug-in tester (B) to check receptacles for correct polarity, grounding and circuit protection; Multimeter (C) to
measure AC/DC voltage, AC/DC current, resistance, capacitance, frequency and duty cycle (model shown is an auto-ranging digital
multimeter with clamp-on jaws that measure through sheathing and wire insulation).
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■ Multimeters
Multimeters are nearly indispensible diagnostic tools traditional way. An example of a clamp‑on multimeter
for doing intermediate to advanced level electrical work can be seen on the next page. Among homeowners,
(as well as automotive and electronics repair). They are however, the most common multimeters these days are
used to measure voltage, current (amperage) and a few digital, auto‑ranging tools that use probes or alligator
other conditions such as continuity, capacitance and clamps at the ends of wire leads for diagnostic work.
frequency. For your home electrical system, by far the Older multimeters that do not have autoranging
most used feature of a multimeter is testing voltage and capability must be pre‑set to estimated calibration
current, although there are occasions where testing for levels before use. Non‑digital multimeters or ammeters
resistance is needed. Among professional electricians, usually have a dial gauge that gives readouts. These
the most common and widely used multimeters have tools are somewhat more difficult to use and are
a clamp‑on ammeter that measures current through less precise. Considering that digital, autoranging
the wire insulation so you don’t have to disconnect multimeters can be found for just a few dollars (the
the circuit and expose bare wire. Most clamp‑on top of the line models cost over $100) there is really
multimeters also are fitted with insertible probes with no good reason not to replace your old device with one
which you can measure voltage and continuity in the that resembles the tools seen on these pages.
Time to replace Capacitance Frequency
Temperature
that Neon Tester ▸ (‑4° to 1832° F
Microamperage
Neon circuit testers are inexpensive and easy to use
Milliamps
(if the light glows the circuit is hot), but they are less
Diode/continuity
sensitive than multimeters and can be unsafe. In Amperage
(current)
some cases, neon testers won’t detect the presence ohms (resistance)
of lower voltage in a circuit. This can lead you to
Voltage (AC and DC)
believe that a circuit is shut off when it is not—a
dangerous mistake. The small probes on a neon circuit Black lead probe
tester also force you to get too close to live terminals
red lead probe
and wires. For the most reliable readings, buy and
learn to use a multimeter. At the very least, switch to a Amperage
input (red lead)
touchless tester like the one on page 107, Step 1. for household
current up to
10 amps
Common input
Neon circuit tester (black lead)
Voltage/
small
amperage/
resistance
input (red
lead)
A digital, autoranging multimeter must be adjusted to
the proper setting for the reading you want to take. The probe
leads also must be inserted into the correct inlet at the bottom
of the tool. Inserting the red lead into the incorrect inlet can
cause the tool to trip an internal fuse. Study your owner’s
manual carefully before using any tool.
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■ How to Measure Current
1 2
Create access to the wires you need to test. In most cases Set the multimeter to test for amperage (current is
this requires that you remove the cover to an electrical service measured in amperes or amps). On some multimeters you
panel or an electrical box (inset). need to select between amperage settings that are above or
below 40 amps. Use the rated amperage of the circuit as a
guide (amperage is printed on the circuit breaker switch).
3 Taking Measurements
at a receptacle ▸
You may use a multimeter to measure for voltage at a
wall receptacle. Regardless of whether the outlet is in
service, if it is live you will get a voltage reading in the
approximate range of the receptacle rating—here, 120
volts. To detect live current, measured in amps, the
receptacle must be in use, with an appliance drawing
from it. Taking an amperage reading in such an instance
will only yield the amount of current being drawn, which
is a factor of the appliance, not the circuit capacity.
Clamp the jaws of a clamp‑on multimeter onto the
conductor or one of the conductors (if more than one) leading
to a circuit breaker. If you are using a non-clamping multimeter,
touch one probe to the screw terminal where the hot lead
is attached to the breaker and touch the other probe to the
metal panel box. The readout on your meter is the amount of
current flowing in that circuit.
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■ How to Measure Voltage
1 2 3
To measure voltage using the Turn the multimeter to the VAC To measure the AC voltage, place
multimeter, you will have to use the two setting to measure AC voltage that is one probe on a grounded surface, such
probes provided with the multimeter found in your house. Set the multimeter as the metallic junction box or the bare
and have access to a live terminal or to VDC if measuring DC voltage, such ground wire. Place the other probe
slot as well as a grounded terminal as in a car or a battery-fed device. on the hot screw terminal or into the
or slot. If your meter has probe holders On some multimeters, like the one receptacle slot associated with the hot
at the top, snap the probes into them. above, you select “V” for voltage then wire. The voltage readout should be in
They are like extra hands. change between AC and DC with the range of 120 volts, plus or minus 5
the”FUNC” button. volts (usually 120 volts in a residence in
the US).
240 VOLTS. You can also measure voltage across the two hot DC Voltage. When testing DC voltage, such as in a car battery,
leads to determine if you have 240 volts. This can be done at you can measure exactly the same way as for AC as long as
your range receptacle, dryer receptacle, or any other 240-volt the meter is set to the DC function. For more accurate results,
receptacle. Place one probe in one of the small slots and the test the voltage while the battery is in use.
other probe in the other slot directly across from it. The voltage
should read 240 volts, plus or minus 5 volts.
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■ How to Test for Continuity
Continuity is a condition in a circuit where the present on the circuit you are testing or damage
conductors form an unbroken pathway through may occur to the meter. You can also measure the
which current may flow. When measuring for resistance in this mode as well.
continuity, always make sure there is no power
1 2
The setting for continuity is an “audible” or diode symbol Verify that the continuity tester is functional by touching
display on the dial. Select this setting. the two probes together. You should hear an alert sound
and/or see a reading of zero ohms (Ohms is a value of the
resistance to current flow).
3 How to Test a 3‑way Switch ▸
Remove the switch from the circuit and place one
of the probes onto the common terminal and the
other probe onto one of the other two terminals used
for the traveler wires. If the meter indicates infinity
ohms or there is no sound, flip the switch and if it is
in working order the meter should read zero ohms
or emit an audible sound. It should only work in one
direction or the other, not both.
To test a circuit, touch one probe to one of the wires on a
given circuit and the other to the second wire of the circuit. If
you hear an audible sound or read a value of resistance other
than zero, you have a complete or unbroken path for current
to flow.
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■ Troubleshooting an Open Neutral
An open neutral is an electrical problem where the low or high voltage, which could damage voltage
circuit is broken on the return path wire or neutral sensitive electronics such as a computer or flat screen
(white wire). When this situation occurs anything TV. The lights will be dim or not work at all, depending
plugged into or connected to this circuit can experience upon where the problem lies within the circuit.
Possible Symptoms of an open Neutral ▸
1. When a whole circuit does not work and the breaker associated with that circuit is operating normally.
2. When the neutral or white wire registers as a hot wire by using a non contact voltage tester when the circuit breaker
is on. This most likely indicates a problem between the main service panel and the utility transformer. The condition
should be readable on other receptacles as well.
3. If you register a voltage lower than 110 volts between the hot and neutral.
4. When the incandescent lights work, but are very dim.
5. When the fluorescent lights are barely lit and are flickering.
6. Discoloration of the wires or exposed copper turning green under the wirenut holding the neutral wires together.
1 2
3 6
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■ How to Troubleshoot an Open Neutral
1 2 3
Verify which lights and receptacles Start at the outlet nearest to the When you encounter a point at
are on the circuit by turning the panel. With the breaker off and using which you read infinity ohms or there is
breaker off and by checking for power a multimeter, check for continuity no continuity between the neutral and
with a non-contact voltage tester. It between the neutral (white wire) and ground wires, the problem lies within
is helpful to either draw a map of the the ground (bare or green wire). These the connections in that box or the box
house or place some tape on every two wires land at the same point just upstream (toward) the panel from
affected opening. electrically in your electrical panel. the one you are checking. Sometimes
If there is an indication of continuity you will see evidence of arcing on the
between these two wires, the neutral wire cap containing the connection
and ground connections are sound and which may include discoloration, or a
you should proceed to the next outlet blackish char near the copper.
as you move away from the panel.
4 5
When you have found the problem connection, remove Turn the circuit breaker back on and verify the proper
the wire cap and, if it is possible, cut the damaged portions of voltage is present at your receptacles by measuring with
the wires off and restrip the wires to expose new copper. Line a multimeter.
the wire ends up and twist on a new wire cap.
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■ Troubleshooting a Short Circuit
Short circuits are a direct connection between the idea behind electrical troubleshooting is to simplify
hot or power wire (black or red) and to either the the circuit by checking it at certain points, in order
neutral (white) or ground (bare) wire. This connection to narrow down the problem point by process of
between the two will cause your circuit breaker or elimination. Generally, the problem is that there is
fuse to blow, which should interrupt power to the a bare ground wire touching a hot terminal within a
affected circuit. switch or an outlet box. There will usually be a black
Short circuits are a common problem and can scorched mark or some sign of an electrical arc where
usually be solved by taking the following steps. The the problem lies.
■ How to Troubleshoot a Short Circuit
1 2
Turn the power off at the affected breaker and verify Using a multimeter set to the ohms or continuity setting,
with a non-contact voltage tester that there is no power check the wires at the panel. Touch one of the probes to the
present. Unplug everything from the receptacles and turn the hot or black wire and the other probe to the ground or bare
lights off on the circuit that is affected. wire. If the meter rings or indicates a low resistance value,
you have a direct short to ground. If the meter does not ring
or indicates a high resistance value the circuit is clear. If the
meter does not ring, start by turning the switches on one-by-
one and re-testing to verify the resistance value. If the meter
indicates a low resistance value or a short circuit, the problem
is downstream from the switch or within the light fixture itself.
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3 4
If the meter consistently rings or indicates a low resistive If the box you have chosen is in fact in the middle of the
value, you will need to find the electrical box that contains the run, it will contain at least two cables. Remove the receptacle
affected circuit. Choose a box that is convenient to open and from the two cables and separate all of the wires.
preferably in the middle of the run, such as a receptacle. Verify
there is no power present by touching all of the wires within
the box with a non-contact voltage tester.
5 6 7
Check the resistance between the Check the wires at the panel to Choose another box in the middle of
black and the ground on both sets of see if the short has cleared. If the short the affected circuit, there by narrowing
cables. One of the cables should cause is clear, the problem lies down stream down the possible problem areas
the continuity alert to ring and the other from the opened box and it is now safe until the short circuit can be positively
should not. Mark the affected one with to turn the breaker back on to help identified and corrected. When you have
a piece of black tape and place wire eliminate further problem points. If the discovered the short circuit, verify the
caps over the exposed ends of the short is still present, the problem lies wires are still in good shape and repair
black wires. between the opened electrical box and the connection.
the panel.
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Types of Wall Switches
W all switches are available in three general types.
To re‑connect or replace a switch, it is important
to identify its type.
terminals, and four‑way switches have four. Most
switches include a grounding screw terminal, which is
identified by its green color.
Single‑pole switches are used to control a set of When replacing a switch, choose a new switch
lights from one location. Three‑way switches are used that has the same number of screw terminals as the
to control a set of lights from two different locations old one. The location of the screws on the switch
and are always installed in pairs. Four‑way switches body varies depending on the manufacturer, but these
are used in combination with a pair of three‑way differences will not affect the switch operation.
switches to control a set of lights from three or Whenever possible, connect switches using the
more locations. screw terminals rather than push‑in fittings. Some
Identify switch types by counting the screw specialty switches (pages 118 to 119) have wire leads
terminals. Single‑pole switches have two screw instead of screw terminals. They are connected to
terminals, three‑way switches have three screw circuit wires with wire connectors.
A wall switch is connected to circuit
wires with screw terminals or with push-in
fittings on the back of the switch. A switch
may have a stamped strip gauge that
indicates how much insulation must be
stripped from the circuit wires to make
the connections.
The switch body is attached to a
Push‑in fittings metal mounting strap that allows it to
be mounted in an electrical box. Several
Grounding screw
rating stamps are found on the strap and
on the back of the switch. The abbreviation
Amperage & Wire UL or UND. LAB. INC. LIST means that the
voltage ratings gauge
rating switch meets the safety standards of the
Underwriters Laboratories. Switches also
are stamped with maximum voltage and
amperage ratings. Standard wall switches
Wire
strip are rated 15A or 125V. Voltage ratings of
Screw terminals
gauge 110, 120, and 125 are considered to be
identical for purposes of identification.
For standard wall switch installations,
choose a switch that has a wire gauge
Wire compatibilty ratings
rating of #12 or #14. For wire systems
with solid-core copper wiring, use only
underwriters
Laboratories Wire release
switches marked COPPER, CU, or CO/ALR.
(uL) approved opening For aluminum wiring, use only switches
for push‑in marked CO/ALR. Note that while CO/ALR
fittings
switches and receptacles are approved by
the National Electrical Code for use with
Mounting screw
aluminum wiring, the Consumer Products
Safety Commission does not recommend
Mounting strap
using these. Switches and receptacles
marked AL/CU can no longer be used with
Front Back
aluminum wiring, according to the National
Electrical Code.
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■ Single‑Pole Wall Switches
A single‑pole switch is the most common type of
wall switch. It has ON‑OFF markings on the
switch lever and is used to control a set of lights, Grounding Note: Position
screw of the screw
an appliance, or a receptacle from a single location. terminals on a
A single‑pole switch has two screw terminals and a switch may vary,
depending on
grounding screw. When installing a single‑pole switch, manufacturer
check to make sure the ON marking shows when the
switch lever is in the up position.
In a correctly wired single‑pole switch, a hot Switch lever Two screw
terminals
circuit wire is attached to each screw terminal.
However, the color and number of wires inside the
switch box will vary, depending on the location of the
switch along the electrical circuit.
If two cables enter the box, then the switch lies in
the middle of the circuit. In this installation, both of
the hot wires attached to the switch are black.
If only one cable enters the box, then the switch
lies at the end of the circuit. In this installation
(sometimes called a switch loop), one of the hot wires A single‑pole switch is essentially an interruption in the black
is black, but the other hot wire usually is white. A white power supply wire that is opened or closed with the toggle.
hot wire should be coded with black tape or paint. Single-pole switches are the simplest of all home wiring switches.
■ Typical Single‑Pole Switch Installations
Grounding Groundingwire
wires
Grounding
wire
Neutral out
Power out
Available
neutral
Power out
Neutral in
Power in Power in
Two cables enter the box when Old method: One cable enters the Code change: In new switch wiring,
a switch is located in the middle of a box when a switch is located at the end the white wire should not supply current
circuit. Each cable has a white and a of a circuit. In this installation, both of to the switched device and a separate
black insulated wire, plus a bare copper the insulated wires are hot. The white neutral wire should be available in the
grounding wire. The black wires are wire should be labeled with black tape switch box.
hot and are connected to the screw or paint to identify it as a hot wire. The
terminals on the switch. The white wires grounding wire is connected to the
are neutral and are joined together with switch grounding screw.
a wire connector. Grounding wires are
pigtailed to the switch.
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■ Three‑Way Wall Switches
Three‑way switches have three screw terminals and
do not have ON‑OFF markings. Three‑way
switches are always installed in pairs and are used to
control a set of lights from two locations.
One of the screw terminals on a three‑way switch
Traveler screw
is darker than the others. This screw is the common terminals
screw terminal. The position of the common screw
terminal on the switch body may vary, depending on
the manufacturer. Before disconnecting a three‑way
switch, always label the wire that is connected to the
common screw terminal. It must be reconnected to Common screw
the common screw terminal on the new switch. terminal
The two lighter‑colored screw terminals on
a three‑way switch are called the traveler screw
terminals. The traveler terminals are interchangeable,
so there is no need to label the wires attached to them. Grounding screw
Because three‑way switches are installed in terminals
pairs, it sometimes is difficult to determine which of
the switches is causing a problem. The switch that
receives greater use is more likely to fail, but you may
need to inspect both switches to find the source of
the problem.
■ Typical Three‑Way Switch Installation
Two cables enter the box: one
Traveler screw terminals Grounding wires Two‑wire cable cable has two wires, plus a bare
copper grounding wire; the other cable
has three wires, plus a ground. The
black wire from the two-wire cable is
connected to the dark common screw
terminal. The red and black wires from
the three-wire cable are connected to
the traveler screw terminals. The white
neutral wires are joined together with a
wire connector, and the grounding wires
are pigtailed to the grounded metal box.
Common screw terminal Three‑wire cable
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■ How to Replace a Three‑Way Wall Switch
1 2
Turn off the power to the switch at the panel, and then Test for power by touching one probe of the circuit tester to
remove the switch cover plate and mounting screws. Holding the the grounded metal box or to the bare copper grounding wire
mounting strap carefully, pull the switch from the box. Be careful and touching the other probe to each screw terminal. Tester
not to touch the bare wires or screw terminals until they have should not glow. If it does, there is still power entering the box.
been tested for power. Note: If you are installing a new switch Return to the panel, and turn off the correct circuit.
circuit, you must provide a neutral conductor at the switch.
3 4 5
Common screw terminal Common screw terminal
Locate the dark common screw Connect the common wire to the Connect the remaining two circuit
terminal, and use masking tape to dark common screw terminal on the wires to the screw terminals. These
label the “common” wire attached to it. switch. On most three-way switches, wires are interchangeable and can be
Disconnect wires and remove switch. the common screw terminal is black. connected to either screw terminal.
Test the switch for continuity. If it tests Or it may be labeled with the word Carefully tuck the wires into the box.
faulty, buy a replacement. Inspect wires COMMON stamped on the back of the Remount the switch, and attach the
for nicks and scratches. If necessary, clip switch. Reconnect the grounding screw, cover plate. Turn on the power at
damaged wires and strip them. and connect it to the circuit grounding the panel.
wires with a pigtail.
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■ Four‑Way Wall Switches
Four‑way switches have four screw terminals and
do not have ON‑OFF markings. Four‑way switches
are always installed between a pair of three‑way Line 1 screw
terminals
switches. This switch combination makes it possible
to control a set of lights from three or more locations.
Four‑way switches are common in homes where
large rooms contain multiple living areas, such as a
kitchen opening into a dining room. Switch problems
in a four‑way installation can be caused by loose
Line 2 screw
connections or worn parts in a four‑way switch or in terminals
one of the three‑way switches (facing page).
In a typical installation, there will be a pair of
three‑wire cables that enter the box for the four‑way
switch. With most switches, the white and red wires
from one cable should be attached to the bottom or
top pair of screw terminals, and the white and red
wires from the other cable should be attached to the
Note: Position
remaining pair of screw terminals. However, not all of the screw
terminals on a
switches are configured the same way, and wiring switch may vary,
configurations in the box may vary, so always study the depending on
manufacturer.
wiring diagram that comes with the switch.
■ Typical Four‑Way Switch Installation
Grounding wires
Available
neutral
Four wires are connected to a four‑way switch. The red Switch variation: Some four-way switches have a wiring
and white wires from one cable are attached to the top pair guide stamped on the back to help simplify installation. For the
of screw terminals, while the red and white wires from the switch shown above, one pair of color-matched circuit wires
other cable are attached to the bottom screw terminals. In will be connected to the screw terminals marked LINE 1, while
new switch wiring, the white wire should not supply current the other pair of wires will be attached to the screw terminals
to the switched device, and a separate neutral wire should be marked LINE 2.
available in the switch box.
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■ How to Replace a Four‑Way Wall Switch
1 2
Turn off the power to the switch at the panel, and then remove the switch cover Disconnect the wires and inspect
plate and mounting screws. Holding the mounting strap carefully, pull the switch from them for nicks and scratches. If
the box. Be careful not to touch any bare wires or screw terminals until they have necessary, clip damaged wires and strip
been tested for power. Test for power by touching one probe of the neon circuit tester them. Test the switch for continuity. Buy
to the grounded metal box or bare copper grounding wire and touching the other a replacement if the switch tests faulty.
probe to each of the screw terminals. The tester should not glow. If it does, there is still
power entering the box. Return to the panel, and turn off the correct circuit.
3 4
Connect two wires from one incoming cable to the top set Attach remaining wires to the other set of screw terminals.
of screw terminals. Pigtail the grounding wires to the grounding screw. Carefully
tuck the wires inside the switch box, and then remount the
switch and cover plate. Turn on power at the panel.
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■ Double Switches
A double switch has two switch levers in a single
housing. It is used to control two light fixtures or
appliances from the same switch box.
In most installations, both halves of the Tab
switch are powered by the same circuit. In these
single‑circuit installations, three wires are connected To
fixtures
to the double switch. One wire, called the feed Ground
wire (which is hot), supplies power to both halves
of the switch. The other wires, called the switch
leg, carry power out to the individual light fixtures Feed
or appliances.
In rare installations, each half of the switch Single‑circuit wiring: Three black wires are attached to the
is powered by a separate circuit. In these switch. The black feed wire bringing power into the box is
connected to the side of the switch that has a connecting tab.
separate‑circuit installations, four wires are
The wires carrying power out to the light fixtures or appliances
connected to the switch, and the metal connecting are connected to the side of the switch that does not have
tab joining two of the screw terminals is removed (see a connecting tab. The white neutral wires are connected
photo below). together with a wire connector.
Connecting tab
To fixture
Tab removed
Ground
Feed
Separate‑circuit wiring: Four black wires are attached to the switch. Feed wires Remove the connecting tab on
from the power source are attached to the side of the switch that has a connecting a double switch when wired in a
tab, and the connecting tab is removed (photo, right). Wires carrying power from the separate-circuit installation. The tab can
switch to light fixtures or appliances are connected to the side of the switch that be removed with needlenose pliers or
does not have a connecting tab. White neutral wires are connected together with a a screwdriver.
wire connector.
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■ Pilot‑Light Switches
A pilot‑light switch has a built‑in bulb that glows
Tab Neutral
when power flows through the switch to a light fixture
or appliance. Pilot‑light switches often are installed for
Silver
convenience if a light fixture or appliance cannot be
seen from the switch location. Basement lights, garage
lights, and attic exhaust fans frequently are controlled To fixture
by pilot‑light switches. Gold
A pilot‑light switch requires a neutral wire Grounds
connection. A switch box that contains a single
two‑wire cable has only hot wires and cannot be fitted
with a pilot‑light switch.
Feed wire
Pilot‑light switch wiring: Three wires are connected to the
switch. One black wire is the feed wire that brings power into
the box. It is connected to the brass (gold) screw terminal on
the side of the switch that does not have a connecting tab. The
white neutral wires are pigtailed to the silver screw terminal.
The black wire carrying power out to a light fixture or appliance
is connected to the screw terminal on the side of the switch
that has a connecting tab.
■ Switch/Receptacles
A switch/receptacle combines a grounded receptacle
Ground
with a single‑pole wall switch. In a room that does not Neutral wires
Silver
have enough wall receptacles, electrical service can
Tab
be improved by replacing a single‑pole switch with a
switch/receptacle.
A switch/receptacle requires a neutral wire
connection. A switch box that contains a single
two‑wire cable has only hot wires and cannot be fitted
To fixture
with a switch/receptacle. Gold
A switch/receptacle can be installed in one Grounds
of two ways. In the most common installations,
the receptacle is hot even when the switch is off
(photo, right).
Feed
In rare installations, a switch/receptacle is wired
so the receptacle is hot only when the switch is
on. In this installation, the hot wires are reversed,
so that the feed wire is attached to the brass screw Switch/receptacle wiring: Three wires are connected to the
switch/receptacle. One of the hot wires is the feed wire that
terminal on the side of the switch that does not have a
brings power into the box. It is connected to the side of the
connecting tab. switch that has a connecting tab. The other hot wire carries
power out to the light fixture or appliance. It is connected to
the brass screw terminal on the side that does not have a
connecting tab. The white neutral wire is pigtailed to the silver
screw terminal. The grounding wires must be pigtailed to the
green grounding screw on the switch/receptacle and to the
grounded metal box.
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Specialty Switches
Y our house may have several types of specialty
switches. Dimmer switches (pages 96 to 97) are
used frequently to control light intensity in dining
cannot be installed in switch boxes that have only one
cable with two hot wires. It is precisely due to the rise
in popularity of “smart” switches that the NEC Code
and recreation areas. Timer switches and time‑delay was changed in 2014 to require an available neutral
switches (below) are used to control light fixtures wire in newly‑installed switch boxes.
and exhaust fans automatically. Electronic switches If a specialty switch is not operating correctly, you
provide added convenience and home security, and may be able to test it with a continuity tester. Timer
they are easy to install. Electronic switches are switches and time‑delay switches can be tested for
durable, and they rarely need replacement. continuity, but dimmer switches cannot be tested.
Most specialty switches have preattached wire With electronic switches, the manual switch can
leads instead of screw terminals and are connected to be tested for continuity, but the automatic features
circuit wires with wire connectors. Some motor‑driven cannot be tested.
timer switches require a neutral wire connection and
■ Timer Switches
Countdown timer switches can be set to turn lights or to the light fixture. The remaining wire lead is the
fans on and off automatically once each day. They are neutral lead. It must be connected to any neutral
commonly used to control outdoor light fixtures. circuit wires. A switch box that contains only one
Timer switches have three preattached wire cable has no neutral wires, so it cannot be fitted with
leads. The black wire lead is connected to the hot a timer switch.
feed wire that brings power into the box, and the After a power failure, the dial on a timer switch
red lead is connected to the wire carrying power out must be reset to the proper time.
Countdown timer switch. This Occupancy sensor. Many smart Programmable timer switch. A
rocker-type switch gives you the option switches incorporate a motion detector dial-type timer allows you to program
to easily program the switch to shut that will switch the lights on if they the switch to turn on for specific time
off after a specified time: from 5 to 60 sense movement in the room and will periods at designated times of day
minutes. Garage lights or basement also shut them off when no movement within a 24-hour cycle. Security lights,
lights are good applications: anywhere is detected for a period of time. The space heaters, towel warmers, and
you want the light to stay on long model shown above also has a dimmer radiant floors are typical applications.
enough to allow you to exit, but not to function for further energy savings.
stay on indefinitely. These switches often
are used to control vent fans.
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Preset timer switch. This lets you turn on lights, heat lamps, Spring‑wound timer switch. A relatively simple device, this
and other loads for a designated amount of time (10 to 60 timer switch functions exactly like a kitchen timer, employing a
minutes) with one easy push of a button. The green LED at hand-turned dial to and spring mechanism to shut the switch
the bottom of this unit provides a readout of how much time off in increments up to 15 minutes.
is left before the switch shuts off. The model shown is not
compatible with fluorescent ballasts.
Daylight sensor switch. This switch automatically turns on Backlit countdown timer. This digital switch lets you
when light levels drop below a proscribed level. It can also be program lights or other devices to stay on for up to 24 hours
programmed as an occupancy sensor to shut off when the and then shut off automatically. The backlit, LED readout gives
room is vacant and turn on when the room is entered. a countdown, in minutes, of the amount of time left in the
“on” cycle. Up and down buttons let you raise or lower the
remaining time easily, and a manual override button will shut
off the switch until it is turned back on.
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Ground-fault (GFCI) & Arc-fault (AFCI) Protection
GRound-FAult loCAtion RequiRements on all 120-volt receptacles located in garages and
1. Kitchen receptacles. Install ground-fault circuit grade-level areas of unfinished accessory buildings.
interrupt (GFCI) protection on all 120-volt 5. Exterior receptacles. Install ground-fault circuit
receptacles that serve kitchen countertops. This interrupt (GFCI) protection on all 120-volt
does not include receptacles under the kitchen receptacles located outdoors. This does not apply to
sink receptacles located on kitchen walls that do receptacles that are dedicated for deicing equipment
not serve the countertop and receptacles that are and are located under the eaves. This applies to
not within six feet of a sink. holiday lighting receptacles located under the eaves.
2. Kitchen. Install ground-fault circuit interrupt 6. Basement receptacles. Install ground-fault circuit
(GFCI) protection on the outlets that supply interrupt (GFCI) protection on all 120-volt
dishwashing machines. receptacles located in unfinished basements. An
3. Bathroom receptacles. Install ground-fault circuit unfinished basement is not intended as habitable
interrupt (GFCI) protection on all 120-volt space and is limited to storage and work space.
receptacles located in bathrooms. This applies 7. Crawl space receptacles. Install ground-fault
to all receptacles regardless of where they are circuit interrupt (GFCI) protection on all 120-volt
located in the bathroom and includes receptacles receptacles located in crawl spaces. Receptacles
located at countertops, inside cabinets, and along in crawl spaces are not required unless equipment
bathroom walls. This also applies to bathtubs and requiring service is located there.
shower stalls that are not located in a bathroom. 8. Sink receptacles. Install ground-fault circuit interrupt
Install ground-fault circuit interrupt (GFCI) (GFCI) protection on all 120-volt receptacles that are
protection on all circuits serving electrically located within six feet of the outside edge of a sink.
heated floors in bathrooms, kitchens, and around This includes wall, floor, and countertop receptacles.
whirlpool tubs, spas, and hot tubs. 9. Boathouse receptacles. Install ground-fault circuit
4. Garage and Accessory Building receptacles. Install interrupt (GFCI) protection on all 120-volt
ground-fault circuit interrupt (GFCI) protection receptacles located in boathouses.
Ground-fault receptacles and circuit breakers detect A combination ARC-fault circuit breaker detects sparking
unwanted current running between an energized wire and a (arcing) faults along damaged energized wires and detects
grounded wire. these faults between wires. A branch ARC-fault circuit breaker
only detects arcing faults between wires.
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10. Spas, tubs, and other circuits requiring ground‑fault this list, although local building officials may
protection. Install ground‑fault circuit interrupt include these areas by interpretation.
(GFCI) protection on all circuits serving spa tubs, 2. You may provide AFCI protection for the entire
whirlpool tubs, hot tubs, and similar equipment. branch circuit by installing a combination‑type
Refer to the general codes for more information AFCI circuit breaker in the electrical panel where
about receptacles serving these components. the branch circuit originates.
11. Install GFCI circuit breakers and receptacles so 3. You may provide AFCI protection to a branch
that they are readily accessible. circuit using several different combinations of
branch‑circuit type AFCI circuit breakers and
ARC‑FAULT LOCATION REqUIREMENTS branch‑circuit type AFCI receptacles. Refer to
1. Install a combination type or an outlet general codes or your local building inspector for
(receptacle) type arc‑fault circuit interrupter details about these alternate methods.
(AFCI) on all 15‑ and 20‑amp, 120‑volt branch 4. Provide AFCI for branch circuits that are
circuits serving sleeping, family, dining, living, modified, replaced, or extended. You may use
sun, and recreation rooms, kitchens, laundry either of the following methods: (a) install
areas, and parlors, libraries, dens, hallways, a combination‑type AFCI circuit breaker in
closets, and similar rooms and areas. This the electrical panel where the branch circuit
means that 15‑and 20‑amp, 120‑volt branch originates, or (b) install a branch‑circuit type
circuits serving most interior spaces in a home AFCI receptacle at the first receptacle in the
are required to have AFCI protection. Note that existing branch circuit.
garages, basements, utility and mechanical rooms, 5. Install AFCI circuit breakers and receptacles so
and exterior branch circuits are not included in that they are readily accessible.
Receptacles for whirlpool tubs must be GFCI protected.
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Junction Boxes, Device Boxes & Enclosures
A ll electrical boxes are available in different
depths. A box must be deep enough so a switch
or receptacle can be removed or installed easily
without crimping and damaging the circuit wires.
Replace an undersized box with a larger box using
the Electrical Box Fill Chart (see page 124) as a
guide. The NEC also says that all electrical
boxes must remain accessible. Never cover
an electrical box with drywall, paneling, or
wall coverings.
NONMETALLIC BOx INSTALLATION
1. Use nonmetallic boxes only with NM type cable
or with nonmetallic conduit or tubing. You may
use nonmetallic boxes with metallic conduit or
tubing if you maintain the electrical continuity
of the metallic conduit or tubing by installing Box shape is directly related to function, as electrical fixtures
are created to fit on boxes of a particular shape. Octagonal and
a bonding jumper through the box. In many
round boxes generally are designed for ceiling mounting, while
situations it is easier to use a metallic box with square and rectangular boxes are sized for single-pole, duplex,
metallic conduit or tubing. and other standard switch and receptacle sizes.
2. Extend NM cable sheathing at least 1⁄4 inch into a
nonmetallic box knockout opening.
3. Secure NM cable, conduit, and tubing to each
box. You may secure NM cable with cable clamps
inside the box or with compression tabs provided
where the cable enters the box. You do not need
to secure NM cable to a standard single‑gang box
(21⁄4 by 4 inches) mounted in a wall or ceiling if
you fasten the cable not more than eight inches
from the box and if the sheathing enters the box at
least 1⁄4 inch. Measure the eight inches along the
length of the sheathing, not from the outside of
the box.
LIGHT FIxTURE BOx INSTALLATION
1. Use boxes designed for mounting light fixtures if
a light fixture is to be mounted to the box. These
boxes are usually four‑inch round or octagonal.
2. You may use other boxes to mount light fixtures on
walls if the fixture weighs less than 6 pounds and
if the fixture is secured to the box using at least
#6 screws.
3. Support light fixtures weighing at least 50 pounds
independently from the light fixture box. You may
Do not support heavy light fixtures using only the light
use the light fixture box to support light fixtures fixture electrical box. The eye hook supporting this chandelier
weighing less than 50 pounds. Note that ceiling is driven into the same ceiling joist to which the electrical box
fans are not light fixtures. is mounted.
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BOx CONTENTS LIMITATIONS
1. Limit the number of wires, devices (such as switches
and receptacles), and fittings in a box. This limitation
is primarily based on the heat generated by the wires
and devices in the box. The actual size of the box
relative to its contents is a secondary consideration.
2. Use the cubic inch volume printed on the box or
provided in the box manufacturer’s instructions to
determine box volume. Do not attempt to measure
the box volume. Do not estimate box volume from the
volume of similar size boxes. You will probably not get
the same volume as provided by the manufacturer.
3. Use table “Wire Volume Unit” to determine the Boxes must be installed so the front edges are flush with the
volume units required by wires, devices, and finished wall surface, and the gap between the box and the wall
fittings in a box. covering is not more than 1⁄8".
BOx INSTALLATION TOLERANCES
1. Install boxes in non‑combustible material, such as
masonry, so that the front edge is not more than
Wire Volume unit ▸
1
⁄4 inch from the finished surface.
WIrE SIzE (AWG) WIrE VoLuME
2. Install boxes in walls and ceilings made of wood or
14 2.00 in.3
other combustible material so that the front edge
is flush with the finished surface or projects from 12 2.25 in.3
the finished surface. 10 2.50 in.3
3. Cut openings for boxes in drywall and plaster so 8 3.00 in.3
that the opening is not more than 1⁄8 inch from the 6 5.00 in.3
perimeter of the box.
Volume units ▸
Calculate the volume units required by wires, devices, and box. From Table 47, #14 wire uses 2.00 cubic inches and #12
fittings based on the following definitions: wire uses 2.25 cubic inches. Allow 4.5 cubic inches volume
units (2 × 2.25 cubic inches) for each switch or receptacle in
Volume units for current‑carrying wires. Allow one the box based on the volume of the larger #12 NM cable.
volume unit for each individual hot (ungrounded) and neutral
(grounded) wire in the box. Use Table 47 to determine the Volume units for grounding wires. Allow one volume
volume units of common wire sizes. Example: two pieces unit for all grounding wires in the box. Base the volume
of #14/2 NM are in a box. Each piece of this cable contains unit on the largest hot (ungrounded) or neutral (grounded)
one hot (ungrounded) and one neutral (grounded) wire wire in the box.
and one grounding wire. From table “Wire Volume Unit”,
each #14 wire uses 2.00 cubic inches in the box. The total Volume units for clamps. Allow one volume unit for all
volume units required by the hot (ungrounded) and neutral internal cable clamps in the box, if any. Base the volume
(grounded) wires is eight cubic inches. unit on the largest hot (ungrounded) or neutral (grounded)
wire in the box.
Volume units for devices. Allow two volume units for each
device (switch or receptacle) in the box. Base the volume Volume units for fittings. Allow one volume unit for all
units on the largest hot (ungrounded) or neutral (grounded) fittings in the box, if any. Base the volume unit on the largest
wire in the box. Example: NM cable size #14 and #12 are in a hot (ungrounded) or neutral (grounded) wire in the box.
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BOx SUPPORT IN WALLS,
Electrical Box Fill Chart ▸ CEILINGS & FLOORS
1. Provide support for boxes that rigidly and securely
Box SIzE MAxIMuM NuMBEr oF
fasten them in place. You may use nails or screws
AND SHAPE VoLuME uNITS PErMITTED
to support these boxes.
(SEE NoTES BELoW)
2. Protect screws inside boxes so that the threads
14 12 10 8
(If volume not labeled by manufacturer) will not damage the wires.
AWG AWG AWG AWG
3. Wood braces used to support boxes must be at
JuNCTIoN BoxES least one by two inches.
4 × 11⁄4" R or O 6 5 5 4 4. Use “cut‑in” or “old work” retrofit boxes only
4 × 1 ⁄2" R or O
1
7 6 6 5 if they have approved clamps or anchors that
are identified for the location where they
4 × 21⁄8" R or O 10 9 8 7
are installed.
4 × 1 1⁄ 4" S 9 8 7 6
4 × 1 ⁄ 2" S
1
10 9 8 7 DAMP LOCATIONS
4 × 2 ⁄ 8" S
1
15 13 12 10 1. Install a receptacle box cover that is
411⁄16 × 11⁄4" S 12 11 10 8 weatherproof when the cover is closed and a
4 ⁄16 × 1 ⁄2" S
11 1
14 13 11 9
plug is not inserted into a receptacle located in
a damp location. This applies to 15‑amp and
4 ⁄16 × 2 ⁄8" S
11 1
21 18 16 14
20‑amp receptacles. A damp area is protected
DEVICE BoxES from direct contact with water. Refer to the
3 × 2 × 1 1⁄ 2" 3 3 3 2 definition of damp location. You may use a
3 × 2 × 2" 5 4 4 3 receptacle cover suitable for wet locations in a
3 × 2 × 2 ⁄4" 1
5 4 4 3 damp location.
2. Install a watertight seal between a flush‑
3 × 2 × 2 ⁄ 2" 1
6 5 5 4
mounted receptacle and its faceplate. This will
3 × 2 × 2 ⁄4" 3
7 6 6 4 require a gasket or sealant between the finished
3 × 2 × 3 ⁄ 2" 1
9 8 7 6 surface (such as stucco, brick, or siding) and
4 × 2 ⁄ 8 × 1 ⁄ 2"
1 1
5 4 4 3 the faceplate.
4 × 2 ⁄ 8 × 1 ⁄ 8"
1 7
6 5 5 4
WET LOCATIONS
4 × 2 1⁄ 8 × 2 1⁄ 8" 7 6 5 4
1. Install a receptacle box cover that is
Notes: weatherproof when the cover is closed on any
• R = Round; O = Octagonal; S = Square receptacle located in a wet location. This applies
or rectangular
• Each hot or neutral wire entering the box is
to 15‑amp and 20‑amp receptacles in any indoor
counted as one volume unit or outdoor wet location. This applies regardless
• Grounding wires are counted as one volume unit of whether or not a plug is inserted into
in total—do not count each one individually. the receptacle.
• Raceway fittings and external cable clamps do 2. Install a watertight seal between a flush‑
not count. Internal cable connectors and straps
mounted receptacle and its faceplate. This will
count as one volume unit.
• Devices (switches and receptacles mainly) each require a gasket or sealant between the finished
count as two volume units. surface (such as stucco, brick, or siding) and
• When calculating total volume units, any non-wire the faceplate.
components should be assigned the gauge of the
largest wire in the box.
• For wire gauges not shown here, contact your
local electrical inspections office.
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resources
Applied Energy Innovations www.passandseymour.com
Solar, wind, geothermal installations
612 532 0384 Unistrut Metal Framing
www.appliedenergyinnovations.org Solar panel mounts
www.unistrut.com
Black & Decker
Portable power tools and more Westinghouse
www.blackandddecker.com Ceiling fans, decorative lighting, solar outdoor
lighting, & other lighting fixtures and bulbs
Broan‑NuTone, LLC 866 442 7873
Vent fans Purchase here: www.budgetlighting.com
800 558 1711 www.westinghouse.com
www.broan.com
Generac Power Systems
Standby generators and switches
888 436 3722
www.generac.com
Honda Power Equipment/
American Honda Motor Company, Inc.
Standby generators
770 497 6400
www.hondapowerequipment.com
Kohler
Standby generators
800 544 2444
www.kohlergenerators.com
Pass & Seymour Legrand
Home automation products
877 295 3472
Photo Credits
p. 53 photo © Mike Clarke / www.istock.com
p. 74 photo © Jeff Chevrier / www.istock.com
p. 75 photos (top right & lower) courtesy of Generac Power Systems, Inc.
p. 86 photo courtesy of Cabin Fever, featuring McMaster Carr vapor‑tight
light fixtures
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Index
A NEC requirements, 48, 120 freezers, 19
AFCI (arc fault circuit interruption) breakers vs. GFCI, 48 fuse panels. See service panels
installation, 49 compatibility, 7 fuses
location requirements, 121 exercising, 61 catastrophe, 100
NEC requirements, 48 GFCI compatibility, 7
vs. GFCI, 48 installation, 49
air conditioners, central, wattage of, 19 vs. AFCI, 48 G
air conditioners, window measuring current at, 103 garages, 120, 121
circuits for, 40 short circuit troubleshooting, 108–109 garbage disposals, 18
wattage of, 19 slimline breakers, 64 gas pipes, metal, 59–60
amperage circuit indexes, 6, 55 generators
evaluating loads and, 16 circuit maps, 32–47 automatic standby, 79, 85
measuring with multimeter, 103 circuits choosing, 76, 77
appliances arc‑fault protection requirements, 121 manual transfer switch installation, 80–84
circuits for high‑wattage, 39–40 diagnostic tools for testing, 101, 102 outage operation of portable, 79
circuits from small, 38 evaluating loads on, 9, 16–19 selecting backup circuits, 81
NEC requirements, 11 generators and backup, 81 types of, 74–75
arc fault circuit interruption (AFCI) breakers. maps for, 32–47 typical system layout, 76
See AFCI (arc fault circuit interruption) NEC requirements for, 11 See also backup power supply
breakers open neutral troubleshooting, 106–107 GFCI (ground‑fault circuit interrupter) breakers
arc‑fault location requirements, 121 sample kitchen project, 26–29 installation, 49
sample room addition, 22–25 location requirements, 120–121
B troubleshooting short circuits, 108–109 vs. AFCI, 48
backup power supply clamp‑on multimeters, 103 GFCI (ground‑fault circuit interrupter)
transfer switch types, 77 clothes dryers, wattage of, 19 receptacles, 120–121
types of, 74–75 computers, 40 ground fault circuit interrupter (GFCI) breakers.
typical system layout, 76 conduit, nonmetallic electrical boxes and, 122 See GFCI (ground‑fault circuit interrupter)
See also generators continuity, testing for, 105 breakers
baseboard heaters crawl spaces, 120 ground fault circuit interrupter (GFCI)
calculating heating needs, 69 current, measuring, 103. receptacles. See GFCI (ground‑fault circuit
circuits for, 39, 68–69 See also amperage interrupter) receptacles
installation, 240‑volt, 70–71 ground‑fault protection location requirements,
thermostats for, 69 D 120–121
basements, 120, 121 device boxes. See electrical boxes grounding
bathrooms diagnostic tools, 101 service panel upgrades/replacements, 56
circuits for, 32, 41 dining rooms, 13 wiring systems, 58–63
ground‑fault protection requirements, dishwashers, 18, 120 grounding electrode systems, 61–63
120–121 dryers. See clothes dryers grounding rods, installing, 58, 61–63
NEC requirements, 11, 13 duplex receptacles. See receptacles
batteries H
for DC lighting circuits, 100 E hallways, 13
measuring voltage with multimeter, 104 electrical boxes heating and air conditioning
bedrooms, NEC requirements, 13 about nonmetallic, 122 baseboard heater installation, 70–71
boathouses, 120 accessibility and, 122 evaluation of electrical loads and, 17
bonding wiring systems, 58–63 content limits of, 123 thermostats for baseboard heaters, 69
boxes. See electrical boxes damp/wet locations and, 124 wall heater installation, 72–73
branch circuits, 121 depth of, 122
breakers. See circuit breakers fill chart for, 124 I
inspections and, 14–15 inspections
C installation tolerances, 123 planning projects and, 9
cables labeling, 15 preparing for, 14–15
NEC requirements, 12 light fixtures, 122 service panel upgrades and, 57
nonmetallic electrical boxes and, 122 NEC requirements, 12, 122 inspectors, 11
in outbuildings, 90–91, 93 in outbuilding, 90–92
volume of in electrical boxes, 123 shape of, 122 J
volume unit chart for electrical boxes, 123 volume unit chart, 123 junction boxes. See electrical boxes
catastrophe fuses, 100 electrical loads
ceiling fans evaluating, 9, 16–19 K
circuits for, 47 locating wattage information, 18–19 kitchens
supporting, 122 electrical symbols, 21 arc‑fault protection requirements, 121
See also light fixtures electric meters, service panel upgrades/ circuits for, 32
ceilings replacements and, 56–57 GFCI requirements, 120
electrical boxes in, 122–123, 124 electric ranges NEC requirements, 11, 13
light fixtures in circuit maps, 47 in circuit maps, 39 receptacle spacing in, 15
shutting off power for work in, 7 wattage of, 18 sample project circuits, 26–27
See also ceiling fans; light fixtures extension cords, 7
central air conditioners, wattage of, 19 L
circuit breaker panels F laundry rooms
NEC requirements, 12 fixtures arc‑fault protection requirements, 121
See also service panels NEC requirements, 12 NEC requirements, 13
circuit breakers See also light fixtures light bulbs, wattage of, 18
AFCI food disposers, 18 light fixtures
installation, 49 forced‑air furnaces, wattage of, 19 ceiling fans, 47, 122
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Text Page: 126
in circuit maps, 33–35, 41–47 wiring diagrams, 9 pilot‑light switches, 117
DC circuits for, 97–100 drawing, 20–21 speed‑control, 47
electrical boxes for, 122 electrical symbol key, 21 switch‑controlled split receptacles, 36–37
evaluation of electrical loads and, 17 plug‑in testers, 101 switch/receptacles, 117
NEC requirements, 11, 12 power timer switches, 118–119
in outbuildings, 92 shutting off, 6
supporting, 122 testing receptacles for, 6 T
living areas PV (photovoltaic) panels, 94–96 thermostats, for baseboard heaters, 69
arc‑fault protection requirements, 121 timer switches, 118–119
NEC requirements, 11, 13 R touchless circuit testers, 101
sample room addition receptacles troubleshooting
circuits for, 22–23 circuit maps containing, 32–33, 35–40, 43 about, 101
wiring diagrams for, 24–25 GFCI multimeters, 102–105
local codes,11 AFCI breakers and, 48 open neutrals, 106–107
See also National Electrical Code location requirements, 120–121 short circuits, 108–109
inspections and, 14–15
M measuring current at, 103 U
main service panels. See service panels NEC requirements, 11, 12 ufers, 63
meters, service panel upgrades/replacements safety and, 6 UL (Underwriters Laboratories), 6
and, 56–57 short circuit troubleshooting, 108–109 Underwriters Laboratories (UL), 6
microwave ovens, wattage of, 18 spacing of, 15 utility companies, 50, 53
multimeters switch‑controlled split receptacles, 36–37 utility rooms, 13, 121
about, 101, 102 switch/receptacles, 117
measuring current with, 103 testing for power, 6, 104 V
measuring voltage with, 104 repairs, 101 vent fans, 40
testing for continuity, 105 resistance, measuring, 105 voltage, measuring, 104
types of, 102 room heaters, 19 volume unit chart, for electrical boxes, 123
N S W
National Electrical Code safety walls
by area, 13 baseboard heaters and, 68 electrical boxes in, 123, 124
bathrooms, 11 basics of, 6–7 NEC requirements, 11
electrical boxes, 12, 122 screw terminals, wall switches, 110 shutting off power for work in, 7
fixtures, 12 service drops, 50, 51, 57 wall switches
grounding, 12 service laterals, 50–51 in circuit maps, 33–37, 41–47
grounding and, 58 service masts double switches, 116
kitchens, 11 safety and, 7 four‑way
living areas, 11 short roofs and, 57 about, 110, 114
permanent appliances, 11 service panels in circuit maps, 45–46
planning projects and, 8, 11 circuit indexes, 6, 55 typical installation, 114
receptacles, 11, 12 expandability of, 10 four‑way replacing, 115
service panels, 12 finding service size of, 10 installing, 110
switch requirements, 12 grounding main, 60 NEC requirements, 11
wires/cables, 12 location of, 52 pilot‑light switches, 117
neon circuit testers, 102 measuring current at, 103 screw terminals and, 110
NEC requirements, 12 single‑pole
O outbuildings and, 93 about, 110–111
open neutrals planning projects and, 8, 9, 10 in circuit maps, 33–35, 41
about, 106 replacing main, 53–57 typical installation, 111
symptoms of, 106 short circuit troubleshooting, 108–109 three‑way
troubleshooting, 106–107 splicing in box, 177 about, 110, 111
outbuildings upgrading in circuit maps, 42–44
about, 86 equipment for, 52 replacing, 112
ground‑fault protection requirements, new panel location, 52 testing, 105
120–121 permits for, 50 typical installation, 111
installing wiring in, 88–93 replacing main, 53–57 water heaters
materials for wiring, 87 short circuits bonding/grounding wiring systems and,
wiring plan for connecting to main panel, 65 about, 108 58, 59
outdoors troubleshooting, 108–109 wattage of, 19
circuits for, 33 sinks, 120 water pipes, metal
ground‑fault protection requirements, solar lighting. See standalone solar lighting bonding, 58–60
120–121 systems window air conditioners
NEC requirements, 13 speed‑control switches, 47 circuits for, 40
See also outbuildings stairways, 13 wattage of, 19
outlets. See receptacles standalone solar lighting systems wires
about, 94–95 NEC requirements, 12
P DC lighting circuit wiring, 97–100 nonmetallic electrical boxes and, 122
permits, 9, 50 PV (photovoltaic) panel installation, 286 volume of in electrical boxes, 123
pilot‑light switches, 117 subpanels volume unit chart for electrical boxes, 123
planning about, 64 wiring diagrams, 9
evaluating loads, 9, 16–17 connecting to main service panels, 64 wiring plans
examining service panels, 8, 9, 10 installation, 65–67 connecting outbuildings to main panel, 65
locating wattage information, 18–19 outbuildings and, 65, 93 drawing, 20–21
National Electrical Code and, 8 wiring diagrams for, 65 electrical symbol key, 21
permits and, 9 switch‑controlled split receptacles, 36–37 for sample kitchen project, 28–29
sample kitchen project wiring diagrams, switches for sample room addition, 24–25
28–29 in circuit maps, 33–37, 41–47
sample room addition dimmer switches, 47
circuits for, 22–23 measuring current at, 103
wiring diagrams for, 24–25 NEC requirements, 12
AdvAnced Home Wiring ■ 127Edition 41940 - Advanced Home Wiring_064-128.indd 127 10/10/14Edition Job: 41940 Title: CSP - Advanced Home Wiring-4th 12:45 AM 11:05 pm
ge: 126 Text Page: 127
128 ■ ADVANCED HOME WIRING41940 - Advanced Home Wiring_064-128.indd 128 10/10/14Edition Job: 41940 Title: CSP - Advanced Home Wiring-4th 12:45 AM 11:05 pm
Text Page: 128Rather have me do it?
Electrical work is dangerous. I do it safely and to code.