Hold the saw at a low angle; you’ll be less likely
to break blades or cut into studs. Using a ham-
mer, gently crush the plaster between the lines.
Use a utility bar (flat bar) to pry out the lath
strips or drywall section. If you expose any cables
in the walls, use an inductance tester to make
sure they’re not hot. Next, drill through the studs
so you can run cable in the trench. Wherever
there’s an outlet indicated, expand the trench
width to accommodate the boxes.
6. Pull out any nails still stuck in the
Finally, pull any lath or drywall nails from
studs; this will make later repairs
stud edges. They’re easy to overlook because
easier.
they’re small; if you pull them now, patching the
trench will go smoothly.
5. Use a hammer and a flat bar to pry the lath free from
the studs. Work slowly to minimize damage.
electrical Wiring
297
1. for metal boxes, start by
2. Screw the box to the side of a stud.
3. for the best appearance, install sidebyside outlets at
removing knockouts and then insert a
the same height. The piece being plumbed is a data ring,
connector.
which is essentially a face plate without a box. Data lines
have such low voltage that they don’t need to be
protected in an outlet box.
4. run cable to each box.
5. feed cable through cable connectors until you have a 6. Staple the cable within 12 in. of
generous amount to work with—9 in. or 10 in. is plenty.
each box. Here, the electrician drives
staples to the underside of a rough
windowsill.
Pulling Cable To reTrofiT boxes
room to loop the cable and staple it to a stud, it’s
acceptable to staple it to other solid framing,
Once you’ve cut a wiring trench and drilled the
such as the underside of a windowsill.
holes, installing the boxes and pulling cable is
fairly straightforward. If you’re installing metal
sTriPPing nM Cable
boxes, remove knockouts and insert cable con-
WiTh a Cable riPPer
nectors into their openings. Then screw boxes to
studs; screwing is less likely to damage nearby
Most professional electricians favor utility knives
finish surfaces. Be sure that the box will be flush
for removing plastic sheathing. But non-pros
to finish surfaces or, if you’ll install plaster rings
should use a cable ripper to avoid nicking wire
later, flush to the stud edge. Whenever you install insulation. Because the ripper’s tooth is inten-
boxes side by side—as with the outlet and low-
tionally dull (so it won’t nick wire insulation), it
voltage data ring shown—install them plumb and usually takes several pulls to slit the sheathing
at the same height.
completely. Once that’s done, pull back the
Installing cable in remodels can be tricky
sheathing and the kraft paper and snip off both,
because space is tight and you must avoid bend-
using diagonal cutters.
ing cable sharply, which can damage wire insula-
Because cable clamps grip sheathing—not
tion. Install nail plates wherever the edge of the
individual wires—there should be at least 1⁄4 in.
hole is less than 11⁄4 in. from the stud edges. Feed of sheathing still peeking out from under cable
cable through the cable connectors into the
clamps when you’re done. If you leave more than
boxes. Finally, staple the cable to the framing
a 1⁄2 in., you make working with the wires more
within 8 in. of a single-gang box without clamps,
difficult. If you didn’t tighten cable clamps earlier,
or within 12 in. of other boxes. If there’s not
do so now.
298 Chapter 11
If there is only one cable entering a box, just
P r O t I P
cut individual wires to length—typically, 6 in. to
8 in. If there’s more than one cable, you’ll add a
Test new outlets before
6-in. pigtail to each wire group.
patching walls or ceilings. if the
outlet’s not correctly wired, you
sPliCing Cable
can repair it without having to
Electricians call the last stage of rough wiring
rip out a newly installed patch to
making up a box. After removing sheathing from
get access.
cables, rough-cut individual wires about 8 in.
long, group like-wires, and, to save time later,
splice all wire groups.
Typically, electricians start by splicing the
ground wires, which are usually bare copper. (If
they’re green insulated wires, first strip approxi-
mately 3⁄4 in. of insulation off their ends.) If you
use standard wire connectors, trim the ground
wires and butt their ends together, along with a
6-in. pigtail, which you’ll connect later to the
green ground screw of a receptacle.
However, many pros prefer to twist the
ground wires together, leave one ground long,
and thread it through the hole in the end of a
special wire connector (see the top photo on
p. 300). If the box is metal, first bond the ground
A cable ripper slits sheathing without damaging
A crimp tool may be used instead of a
individual wire insulation. Use diagonal cutters to
wire nut to splice ground wires.
wire to the box, using a grounding clip or a
cut free sheathing.
grounding screw.
Splicing hot and neutral wire groups is essen-
tially the same. Trim hot wires to the same
length. Strip 3⁄4 in. of insulation off the cable
wires and the pigtail, and use lineman’s pliers to
twist the wires. Screw on a wire connector. If a
box has more than one circuit in it, all the
grounds must be spliced together, but the
neutrals of the different circuits must be kept
separate.
Once the wire groups are spliced, gently
accordion-fold the wires back into the box until
you’re ready to wire switches and receptacles.
Wiring Receptacles
The long wire of the spliced grounds is looped beneath the Strip about 1⁄2 in. of insulation from
grounding screw in a metal box.
wire ends, and splice likewires
Wiring an electrical device is considered part of
together.
finish wiring—also called the trim-out stage—
when finish walls are in place and painted. At the
trim-out, everything should be ready so that the
electrician needs only a pair of strippers and a
screwdriver or screw gun.
All work in this section must be done with
power off: Use a voltage tester to be sure.
Wiring a duPlex reCePTaCle
The duplex receptacle is the workhorse of house
wiring. Receptacles are so indispensable to mod-
ern life that code dictates that no space along a
wall in a habitable room should be more than
6 ft. from a receptacle and any wall at least 2 ft.
for the two receptacles that will be
fold the wires carefully into the box, and install a mud
wide must have a receptacle.
installed in this box, two sets of
ring. This box is ready for a roughin inspection.
pigtails are needed.
electrical Wiring
299
The rough-in inspection
at the rough-in stage, inspectors will look for a few key signs of a job well done:
cables properly sized for the loads they’ll carry; the requisite number and type of
outlets specified by code; cables protected by nail plates as needed; neat, consis-
tent work throughout the system; and, above all, ground wires spliced and, in metal
boxes, bonded to the box with a ground screw. if grounds aren’t complete, you won’t
pass the rough-in inspection. remember the inspection is usually a spot-check, so
do not count on the inspector to catch every mistake or omission.
at this inspection, only grounds need to be spliced. but since you’ve got the
tools out, it makes sense to splice neutrals in a group, and continuous hot wires
1. When wiring a receptacle, electricians usually start
with the ground. “Wiring in an Orderly Way” on p. 301
(those not attached to switches).
explains why.
When all splices are complete, carefully fold the wire groups into the box. When
you come back to do the trim-out stage, simply pull the wires out of the box, con-
nect wires to devices, and install devices and cover plates.
Connecting circuit wires to a main panel or subpanel is the very last step of an
installation. as noted throughout this book, you should never handle energized
cables or devices. if you are testing circuits, shut off power to manipulate the wir-
ing and set up to test, power up and then test, and then cut the power to continue
the work. remember, 120 volts can kill.
receptacle in Midcircuit
2. next, connect the neutralwire pigtail to a silver screw
terminal. Screw terminals are generally a more secure
zzzzzz
connection than using a spring backwire hole terminal
on a device.
Incoming
Outgoing power
power
(downstream)
Twist-on
wire connectors
Hot
pigtail
3. finally, tighten the hotwire
4. When you finish wiring a
Neutral
pigtail
pigtail wire to a brass screw
receptacle, carefully fold wires into
terminal. Make the connections
the box so the face of the device will
good and tight.
be parallel to the wall. Crooked
devices suggest sloppy work.
Ground
S a f e t y a l e r t
The ground screw must compress
the ground wire evenly. never
By splicing like-wire groups and running pigtails (short wires)
cross the ground wire (or any
to the receptacle in this conventional method, you ensure
wire) over itself because the
continuous current downstream.
5. Push in the receptacle, too, before
screw would touch only that
screwing it to the box. That is, don’t
high spot.
use screws to pull the receptacle into
a packed box—you might strip the
threaded screw holes of a plastic box.
300 Chapter 11
When a duplex receptacle is in the middle of
receptacle at end of Circuit
a circuit, there will be two 12/2 or 14/2 cables
entering the box—one from the power source
and the other running downstream to the next
zzzzzz
Incoming
outlet.
power
To ensure continuity downstream, all wire
groups will have been spliced with wire connec-
Because there
tors during the rough-in stage. A pigtail from
are no receptacles
each splice will need to be connected to a screw
downstream, attach
all wires directly to
terminal on the receptacle. Unless the small tab
the device.
between screw pairs has been removed, you need
to attach only one conductor to each side of the
receptacle.
Loop and install the ground wire to the recep-
tacle’s green grounding screw first. Place the loop
clockwise on the screw shaft so that when the
screw is tightened down, the screw head will grip—
rather than dislodge—the wire.
Next, loop and attach a neutral conductor to a
silver screw terminal. (Some electricians also
tighten down the screw that isn’t used as a matter
of good practice.) Then flip the receptacle over to
access the brass screw terminals on the other
side. If a looped wire end is too wide, use needle-
nose pliers to close it.
Screw down the brass screw so that it grips
the hot wire. Pros frequently use screw guns
for this operation, but weekend electricians
Two-slot receptacles
should tighten the screw by hand to ensure a
solid connection.
receptacles with only two slots are ungrounded. because they are fed by two-wire
Push the wired receptacle into the box by
cable without a ground wire, they are inherently less safe than three-slot recepta-
hand, keeping the receptacle face parallel to the
cles fed with a grounded cable. if existing cables and receptacles are correctly wired
wall. You can hand-screw the device to the box,
and in good condition, most codes allow you to keep using them. should you add
but if you take it slow and use a fresh bit, a cord-
circuits, however, code requires they be wired with grounded cable (12/2 w/grd or
less drill/driver is much easier. Finally, install a
14/2 w/grd) and three-slot receptacles.
cover plate to protect the electrical connections
replacing a two-slot receptacle with a gfCi receptacle can be a cost-effective
in the box and to prevent someone from inadver-
way to add protection to a two-wire circuit. There will still not be a ground wire on
tently touching a bare wire end or the end of a
the circuit, but the gfCi will trip and cut the power if it detects a ground fault. you
screw terminal.
can wire the gfCi receptacle to protect just that outlet or that outlet and all outlets
downstream (away from the power source).
Wiring
Note: if one slot of a two-slot recepta-
In an orderly Way
cle is longer, the receptacle is polarized.
That is, a receptacle’s brass screw terminal
any habit that increases your safety is worth
will connect to a hot wire and, internally,
adopting. When connecting wires to devices,
to the hot (narrow) prong of a polarized
most electricians connect the ground wire first,
two-prong plug. The receptacle’s silver
then the neutral wire, and then the hot wire.
screw terminal connects to neutral wires
When disconnecting wires, they reverse the
and,
internally, to the neutral (wide) prong
order: disconnect the hot first, then the neutral,
of a polarized plug.
then the ground wire. Because the ground wire
offers the lowest impedance path to ground, it
makes sense to leave it connected as long as
possible. Follow this order even if you’re work-
receptacles with two slots (instead of three)
ing on circuits that are disconnected: as veteran
are nongrounding types. If the two slots are
the same length, the receptacle is also nonelectricians say, “treat every conductor as if it
polarized and should be replaced with a
were live and you’ll stay alive.”
polarized nongrounding receptacle.
electrical Wiring
301
When a receptacle is at the end of a circuit—
gfCi receptacle, single-location Protection
where only one cable feeds an outlet—there’s no
To devices
need for pigtails. Just attach incoming wires
zzzzzz
downstream
directly to the receptacle as shown in the illustra-
Incoming
power
tion on p. 301. As with pigtail wiring, connect
the ground wire first, then the neutral, then the
Neutral
hot wire.
wires spliced
Hot
wires spliced
Wiring a gfCi reCePTaCle
When wiring a GFCI receptacle, it’s important
to connect incoming wires (from the power
source) to the terminals marked “line” on the
Line
back of the receptacle. To distinguish line and
brass
load wires during rough-in, write each term on
small pieces of the cable sheathing and slip them
over the appropriate wires before folding them
into the box.
Line silver
Ground
The GFCI shown here is something of a
wires spliced
hybrid because it allows you to loop stripped
Ground screw
wire ends around the screw terminals or to leave
the stripped wire ends straight and insert them
This configuration provides GFCI protection at one location
into holes in the back of the device—also known
—say, near a sink—while leaving devices downstream unprotected.
as back-wiring. In this case, back-wiring is
Here, splice hot and neutral wires so the power downstream is
continuous and attach pigtails to the GFCI's "line" screw terminals.
acceptable because you must tighten screws on
With this setup, receptacle use downstream won’t cause nuisance
Renovation 4th Edition Page 70