secure cable to boxes to protect connections
should a cable get yanked.
inside the box, so wire splices or connections to
devices cannot get yanked apart or compromised.
A metal locknut connector consists of
Cable clamps in metal boxes also keep wires
two separate pieces. Two screws
from being nicked by burrs created when metal
tighten down to grip the cable.
box knockouts are removed (see p. 290).
The exception to this rule is single-gang plas-
tic boxes. If framing is exposed and cable can be
stapled within 8 in. of the box, code doesn’t
require cable clamps in a single-gang plastic box.
However, two-gang plastic boxes must have cable
clamps—typically, a plastic tension clip that
keeps cables from being pulled out. And, as noted
earlier, all cut-in boxes must contain cable clamps.
Two-piece locknut connectors are still the most
Plastic snapin connectors snap easily
common type of clamp, but professional electri-
into place and don’t require
tightening to secure cable.
cians racing the clock swear by plastic snap-in
cable connectors, which seat instantly and grip
NM cable tightly.
Wire connectors. Wire connectors, often called
by the brand name Wire-Nut®, twist onto a group
of wires in a box to splice them together and
ensure a solid mechanical connection. The
importance of solid connections between spliced
wires (or between wires and devices) can’t be
overstated. If wires work loose, electricity can
leap over the gaps (arc) between them and cause
a house fire. Wire connectors are sized according
to the number of wires and wire gauge they can
accommodate; each size is color-coded.
Choosing reCePTaCles
and sWiTChes
Receptacles and switches can differ greatly in
quality. Over the life of the device, the difference
in price is trivial, but the difference in perfor-
mance can be substantial. For this reason, buy
A divided pouch transforms a 5gal.
quality. As shown in the photo on p. 284, cheap
bucket into a portable hardware store
receptacles are pretty much all plastic. Their thin
of wire connectors, cable clamps,
screws, staples, and other small items.
electrical Wiring
283
either 14AWG or 12AWG wire. It’s much easier to
work with 14-gauge wire, so general illumination
a neW KInd oF nut
circuits (to which general use receptacles are
splicing with twist-on wire nuts can be
wired) commonly are wired with 14-gauge cable.
problematic because stranded wire
The NEC specifies 20-amp circuit protection for
small appliance branch circuits, which are
tends to slide down solid wire when
required for kitchen countertop receptacles and
you join solid wires to twisted-strand
dining room receptacles. The only case in which
fixture leads. Wago Wall-nuts™
a 20-amp receptacle is required by the code is
simplify the task: strip the wire ends
when there is a single receptacle on a 20-amp
the specified amount, and then push
circuit; it may be a 15-amp receptacle. There’s no
them into nut ports that hold the wires
good reason to use a 20-amp receptacle in
fast. the clear plastic housing allows
residential wiring. It is a good idea to use
you to see if the wires are connected,
“specification-grade” or higher-quality 15-amp
and the ports grasp both stranded and
receptacles. It used to be that to get a good
solid wire well. Wagos are also a good
quality receptacle, you had to use a 20-amp
solution if the box has very short wires.
version. Not any more. GFCI receptacles come
in both 15-amp and 20-amp versions, and a
15-amp GFCI receptacle is the best choice for
residential wiring.
The 2011 NEC requires that receptacles
(including GFCI receptacles) be tamper-resistant,
metal mounting tabs will distort easily, and they
except for those more than 51⁄2 ft. above the floor,
tend to crack if subjected to heavy use.
and those behind a not-easily moved appliance,
High-quality receptacles and switches tend to
those that are part of a light fixture, and non-
have heavier nylon faces and may be reinforced
grounding receptacles used for replacements in
with metal support yokes that reinforce the back
non-grounding wiring.
of the devices.
In addition, you can obtain various kinds of
Another telling detail is how wires are
specialty 15-amp receptacles, such as weather-
attached—whether they’re screwed to terminals
resistant (WR) receptacles for damp locations,
on the side of the device, inserted into the back of recessed receptacles in which clock wires can be
the device and held by internal clamps tightened
hidden, and covered floor receptacles. In addi-
by the side screws (clamp back-wired, which is
tion, there are receptacles specifically matched to
very good), or inserted into holes in the recepta-
the plugs of 30-amp, 40-amp, and 50-amp appli-
cle back and held by small spring bronze strips
ances. Your electrical supplier can help you find
(spring back-wired, which is fast but not as reliable the right receptacle for your needs.
as the other methods). Again, better-quality devices
An exciting new entry to the switch family is
have better mechanisms for gripping wire.
the wireless switch, a great boon to renovators
Most general-use household receptacles are
because wireless switches can be installed with-
rated for 15-amp circuits and can be wired with
Betterquality receptacles and switches are usually heftier and more reliable
receptacles for different loads. Clockwise from upper left: 15amp surge
than cheaper ones. The quality receptacle on the right has a nylon face, and its
suppressor, 50amp range (250v), 30amp dryer (125/250v), 20amp duplex,
back is reinforced with a brass yoke.
15amp duplex, and GfCI 15amp with 20amp feedthrough. In new
installations, 30amp and 50amp receptacles must be 4pole models.
284 Chapter 11
out tearing up walls and ceilings. See “Installing
neutral slot
15 amp
20 amp
a Wireless Switch” on p. 308.
hot slot
Matching load ratings. Circuit components
must be matched according to their load ratings.
neutral screw
hot screw
That is, a 20-amp receptacle must be fed by
(silver)
(brass)
12AWG cable, which is also rated at 20 amps,
and protected by a 20-amp breaker or fuse. A
15-amp receptacle or switch should be fed by
ground slot
14AWG cable, which is rated for 15 a
mps, and
green grounding
screw
protected by a 15-amp breaker or fuse. (There’s
no harm in wiring a 15-amp receptacle with
12-gauge wire if that’s what you have on hand, as
long as the circuit is protected by a 15-amp
breaker.) Accordingly, a 20-amp circuit (wired
with 12-gauge cable) can be wired with 15-amp
Polarized receptacles. The 20amp receptacle (at right) has a Tshaped neutral slot so it can receive
receptacles.
a special 20amp plug in addition to standard 15amp plugs. But 15amp receptacles cannot
receive 20amp plugs. Both receptacles are also polarized, so that only the large blade of a plug can
NM cable manufacturers have voluntarily
fit into the large slot of the receptacle.
chosen to color-code the cable sheathing for the
commonly used gauges to help correctly match
wire size to breakers: White sheathing denotes
14-gauge wire; yellow sheathing, 12 gauge; and
orange sheathing, 10 gauge.
Rough-in Wiring
Rough-in wiring refers to the first phase of a wir-
ing installation. It is the stage at which you set
outlet boxes and run electrical cable to them—
as opposed to finish wiring, or connecting wires
to devices and fixtures.
Rough-in wiring is pretty straightforward
when studs and joists are exposed. Whether a
house is new or old, running wires through
exposed framing is called new work, or new con-
struction. If the framing is covered with finish
surfaces such as plaster and drywall, however,
the job is referred to as remodel wiring, or “old
work.” Remodel wiring is almost always more
complicated and costly because first you must
drill through or cut into finish surfaces to install
boxes and run cable, and later you need to patch
the holes you made.
When running cable around doors
rough-in PreliMinaries
Polarized and windows, find the easiest path.
Consider drilling through top or
Wait until rough carpentry is complete before
reCePtaCles
bottom plates and running cable in
you begin rough-in wiring. Part of an electrician’s
the space above or below.
job is setting boxes so they’ll be flush to finished
receptacles, plugs, and fixtures are polarized so
surfaces. Before an electrician starts working,
they can fit together only one way. a recepta-
modifications to the framing—such as furring
cle’s brass screw terminal connects to hot wires
out or planing down irregular studs and ceiling
and, internally, to the hot (narrow) prong of a
joists—must be complete.
polarized plug. the receptacle’s silver screw ter-
Wait until the plumbers are gone. Waste pipes
minal connects to neutral wires and, internally,
are large and often difficult to locate, which usu-
to the neutral (wide) prong of a polarized plug.
ally means a lot of drilling and cutting into studs
Finally, the green ground screw connects to the
and joists. Once the plumbing pipes are in place,
you’ll clearly see what obstacles you face and will
ground wire and the grounding prong of the plug.
have more room to move around.
electrical Wiring
285
similar tasks. You’ll waste less time. In general,
the sequence of rough-in tasks looks like this:
remodel Wiring safety essentials
1. Walk the room with plans, marking outlet
before removing box covers or handling wires, turn off the power to the area and
locations on walls and the ceiling.
use a voltage tester to be sure it is off.
2. Snap chalklines or shoot laser lines to pin-
first, remove the fuse or flip off the circuit breaker controlling the circuit and
point box elevations.
post a sign on the main panel warning people of work in progress. better yet, if
3. Attach boxes to studs and ceiling joists.
you’ve got circuit breakers, do as the pros do and install a breaker lockout so it will
be impossible for anyone to turn it on. breaker lockouts are available at electrical-
4. Drill holes for cable runs.
supply houses and most home centers.
5. Pull cable through holes and into boxes.
Testing for power is particularly important in remodel wiring because walls and
6. Make up boxes—strip wire ends, splice
ceilings often contain old cables that are energized. here, a non-contact tester is
current-carrying conductors, make up (splice)
especially useful. simply touch the tester tip to cable sheathing or wire insulation.
grounds, attach mud rings, and push wires into
you don’t have to touch the tester tip to bare wires to get a reading: if a cable, wire,
boxes.
or electrical device is energized, the tip will glow. a non-contact tester can detect
7. Rough-in inspection. (See the box on the
voltage through cable sheathing.
facing page and “The Rough-in Inspection”
Whatever tester you use, test it first on an outlet that you know is live to make
on p. 300.)
sure the tester is working properly.
After the inspection, finish surfaces are
installed. Then, at the trim-out stage or finish stage,
wires are attached to the devices and fixtures.
Always use a voltage tester to test
for power before handling cables,
ordering MaTerials
devices, or fixtures. Here, a noncontact voltage tester detects
In general, order 10% extra of all boxes and cover
voltage through cable insulation.
plates (they crack easily) and the exact number
of switches, receptacles, light fixtures, and other
devices specified on the plans. It’s OK to order
one or two extra switches and receptacles, but
because they’re costly, pros try not to order too
many extras.
Cable is another matter altogether.
Calculating the amount of cable can be tricky
because there are many ways to route cable
between two points. Electricians typically mea-
sure the running distances between several pairs
of boxes to come up with an average length. They
Check your plans often. If there’s not a table
then use that average to calculate a total for each
on site where you can roll out your electrical
room. In new work, for example, boxes spaced
plans, staple them to a stud—preferably at eye
12 ft. apart (per code) take 15 ft. to 20 ft. of cable
level so you can read them easily. Checking and
to run about 2 ft. above the boxes and drop it
rechecking the plans is particularly important if
down to each box. After you’ve calculated cable
you’re not a professional electrician.
for the whole job, add 10%.
Be flexible. As you lay out devices, you’ll real-
Cable for remodel jobs is tougher to calculate
ize that not everything specified on the plans is
because it’s impossible to know what obstruc-
possible; most plans are developed without
tions hide behind finish surfaces. You may have
knowing exactly what the framing looks like or
to fish cable up to the top of wall plates, across
where obstructions are. Be flexible and choose a
an attic, and then down to each box. Do some
solution that makes sense.
exploring, measure that imaginary route, and
During a roughin inspection,
again create an average cable length to multiply.
inspectors demand solid ground
organize your Work
If it takes, say, 25 ft. for each pair of wall boxes
wire splices and, in metal boxes, a
Perform one task at a time. Each task—such as
and you have eight outlets to wire, then 8 outlets
ground screw or clip that secures
setting boxes or drilling—requires a different set
× 25 ft. = 200 ft. Add 10%, and your total is 220 ft.
the ground wire.
of tools. So once you have the tools out to do a
Because the average roll of wire sold at home
given task, go around the room and complete all
centers contains 250 ft., one roll should do it.
286 Chapter 11
rouGh-In reCaP: electrical Code
Circuit breakers, wiring, and devices must be correctly sized for the loads they carry. For example,
20-amp circuits require 12aWg wire. receptacles can be rated for either 15 or 20 amps. mismatching
circuit elements can lead to house fires.
all wire connections must be good mechanical connections. there must be good pressure between
the connectors you are joining, whether wires are spliced together or connected to a device. In general,
P r O t I P
devices with screw terminals are more reliable than back-wired (stab-in) devices whose internal spring
clamps can weaken and allow the wire to become loose.
When marking box locations
all wire connections must be housed in a covered box.
on finish surfaces, use a pencil—
Boxes must be securely attached to framing (or the wall, in old work)so that normal use will not
never a crayon, grease pencil,
loosen them.
or a felt-tipped marker. Pencil
Box edges must be flush to finish surfaces. In noncombustible surfaces (drywall, plaster), there
marks will not show through new
may be a 1⁄4-in. gap between the box edge and the surface. But in combustible surfaces, such as wood
paint. also, grease pencils and
paneling, there must be no gap.
crayons can prevent paint from
Renovation 4th Edition Page 67