either side to engage internal clamps that grip
tripping of the GFCI receptacle.
the wire, thus ensuring a solid connection. Avoid
receptacles that lack this feature. They aren’t reli-
able. (Back-wired switches, on the other hand,
rarely fail.)
If the GFCI is going to protect users at a
single outlet, attach incoming wires only to LINE
screw terminals. The yellow tape across one set
of screws indicates that they are load terminals.
If you are hooking up the device to protect only
a single point of use, leave the tape in place and
connect wires only to the screw terminals
marked “line.” After attaching the ground pigtail,
screw down the silver screw to secure the
neutral pigtail.
Connect the hot pigtail to the brass screw last,
then push the device into the box carefully, hand
screw it to the box, and install a cover plate.
Quality GfCI receptacles can be
By using pigtails, you wire a GfCI
Feeding the circuit through a GFCI receptacle.
reliably wired by inserting stripped
receptacle to protect only itself and
If you want to use a single GFCI receptacle to
wire ends into terminal holes in the
not outlets downstream.
protect downstream outlets, attach the outgoing
back where screws tighten pressure
plates to hold the wires, or by
wires to the “load” terminals of the GFCI recepta-
attaching wires to screw terminals on
cle. That is, connect incoming and outgoing cable
the side. note the “lOAD” and “lInE”
wires directly to the device rather than using pig-
descriptors; they are important.
tails. Again, it’s important to connect incoming
wires to the terminals marked “line” and outgo-
ing wires to terminals marked “load.”
Wiring a split-tab receptacle. Standard duplex
A GfCI receptacle wired to protect a
receptacles have a small metal tab between the
single outlet has just three wires
brass screw terminals. The tab conducts power to
attached: a ground wire to the
both terminals, even if you connect a hot wire to
ground screw and a neutral wire and
just one terminal. However, if you break off and
a hot wire attaching to terminals
remove the tab, you isolate the two terminals and
marked “lInE.”
302 Chapter 11
gfCi receptacle, Multiple-location
S a f e t y a l e r t
Protection
From power
zzzzzz
if you install three-prong
source
receptacles on an ungrounded
circuit, the neC requires the new
receptacles be gfCi-protected
and that you label affected
receptacles “no equipment
ground.”
Spliced
ground
wires
A GfCI receptacle wired to protect
outlets downstream does not use
pigtails for hot and neutral wires.
Incoming wires from the power
source attach to terminals marked
To devices
“lInE”; outgoing wires attach to
downstream
LINE
T
terminals marked “lOAD.”
NEUTRAL
HO
WIrInG A SPlITTAB rECEPTAClE
Neutral
LOAD
NEUTRAL
THO
*Devices
include
Hot
receptacles,
switches, and
light fixtures.
A GFCI receptacle can protect devices* downstream
if wired as shown. Attach wires from the power source
to terminals marked "line." Attach wires continuing
downstream to terminals marked "load." As with any
receptacle, attach hot wires to brass screws, white wires
to silver screws, and a grounding pigtail to the ground
screw. Note: Here only ground wires are spliced; hot and
neutral wires attach directly to screw terminals.
1. To convert a standard duplex
2. Connect the ground wire to the
receptacle into two single
green grounding screw, then the
create, in effect, two single receptacles—each of
receptacles, start by twisting off the
neutral to one of the silver screw
which requires a hot lead wire to supply power.
small metal tab between the two
terminals.
brass screw terminals.
This technique, known as split-tab wiring, is
often used to provide separate circuits from a
single outlet, a configuration commonly used
when connecting a disposal and a dishwasher.
The disposal receptacle is almost always con-
trolled by a switch, which allows you to turn off
the disposal at another location. To supply two
hot leads to a split-tab receptacle, electricians
usually run a 12/3 or 14/3 cable.
To create a split-tab receptacle, use needle-
nose pliers to twist off the small metal tab
between the brass screws. Next, connect the bare
ground wire to the green grounding screw on the
device and connect the white neutral wire to a
silver screw. If you keep a slight tension on the
wires as you tighten each screw, they’ll be less
likely to slip off.
3. Connect the hot wires last.
4. A correctly wired splittab
Flip the receptacle over to expose the brass
removing the tab creates, in effect,
receptacle. Typically, one wire is
screws on the other side, and connect a hot lead
two receptacles, so each needs a
controlled by a switch.
to each brass screw. If you’re running 12/3 or
separate hot wire. It’s common to use
14/3 cable, one hot wire will typically be red and
a 12/3 or 14/3 cable for splittab
the other black. Finally, push the receptacle into
circuits. Typically, one hot wire of the
cable will be black, the other red.
electrical Wiring
303
the box, install the mounting screws, and apply
insert wires into holes on the back of the device.
the cover plate.
Here, back-wiring is acceptable because you
Although this 15-amp split-tab receptacle
must tighten screws on either side to engage
is fed with 12/3 cable (rated for 20 amps), there’s
internal clamps that grip the wire and ensure a
no danger of the load exceeding the rating of
solid connection.
the receptacle. Because of the configuration
of the slots, the receptacle can receive only a
Wiring Switches
15-amp plug.
Because switches interrupt only hot wires, you’d
think they’d all be easy to wire. As you can see
baCksTab or Push-in deviCes
from the wiring schematics on pp. 314–315, how-
A backstab switch. After stripping the Cheap backstab receptacles have holes in the
ever, switch wiring can be q
uite complex, espe-
wire end, insert it into a back port/
back, into which you push stripped wire ends,
cially three-way and four-way switches and
hole until the wire bottoms, then pull which are grabbed by strips of spring metal.
switches with electronic components. So follow
gently to make sure that the device’s
They’re quicker to wire than screw terminals, but the manufacturer’s instructions carefully. Simple
internal clamp has gripped the wire
the receptacle’s internal spring clamps can weak-
securely.
switches have a top and bottom, so wire the
en, leading to loose wires, flickering lights, and
switch correctly.
arcing. Moreover, each time you insert and
Before connecting wires to a switch (or dis-
remove plugs, the receptacles move slightly,
connecting wires, if you’re replacing one) use a
which increases the likelihood of clamp failure.
voltage tester to make sure that the wires aren’t
Manufacturers have stopped making back-wired
energized. Test with the switch both on and
20-amp receptacles. Backstab switches, on the
off to be sure.
other hand, rarely fail.
Wiring a single-pole switch. The most com-
Also, high-quality devices such as the GFCI
monly installed switch, a single-pole, is straight-
receptacle shown in the photo on p. 302 allow
forward to wire. Spliced together during the
you to loop wires around its screw terminals or
rough-in stage, the neutral wires stay tucked in
the outlet box. Pull ground and hot-wire groups
out of the roughed-in box. Use the hole in the
handle of your wire strippers or use needle-nose
pliers to loop the conductor ends so they can be
wrapped around the screw terminals.
light fixture at end of
Cable run
zzzzzz
1. When wiring switches, leave
2. next, attach the hot wires to terminals. One wire is
To fixture
neutral wires tucked in the box.
considered the hot (from the power source), whereas the
Switches interrupt the current
other is the switch leg (power going out to the fixture).
flowing through hot wires only.
With a singlepole switch, it doesn’t matter which hot
Attach the ground wire first.
wire you attach to which screw.
Ground
Neutral
Incoming power
Hot
3. Wires are ready to be tucked into 4. Straighten switches in the box, and tighten the screws
the box.
carefully so you don’t strip the box’s threads. Using a drilldriver will speed the task.
304 Chapter 11
Wiring a “switch loop”:
WIrInG switches
the historical Method
Before connecting or disconnecting wires to a
zzzzzz
switch, use a non-contact tester to make sure
In the “old school” way of wiring a switch loop,
that the power to the switch outlet is off.
a single length of two-wire cable serves as a
test with the switch flipped both on and off
Ground
switch leg. The white wire in the cable is taped
to be sure.
black to show that it is being used as a hot wire.
Because switches interrupt only hot wires,
It was a good solution because it conserved
you’d think they’d all be easy to wire. as you will
copper and was quick to wire, but it has been
superseded by the method shown below.
see, however, switch wiring can also be quite
complex, especially three-way and four-way
switches and switches with electronic compo-
nents. Follow the manufacturer’s instructions
Hot white wire
carefully.
taped black
First, attach the ground wire to the green
A single length of two-wire cable
grounding screw on the switch. Orient the wire
serves as a switch loop
loop in a clockwise direction—the same direction
the screw tightens. When the loop faces the
other way, it can be dislodged as the screw head
is tightened.
Next, connect the hot wires to the switch ter-
minals, again orienting wire loops clockwise.
One black wire is hot (power coming in), and the
other is the s witch leg (power going out to the fix-
ture). With a single-pole switch, however, it
doesn’t matter which wire you attach to which
screw. Generally, pros attach the hot wire last, as
they attach the hot wire on a receptacle last.
Once the ground and hot wires are connect-
ed, the switch can be tucked into the box. Always When an outlet or fixture box is closer to the power
As is customary, connect the ground
push the device into the box by hand until it’s
source than to the switch box, it’s common to run a single
wire first, then connect the hot wire
length of 12/2 or 14/2 cable as a switch loop. Because the
and the switchleg wire to screw
flush to the wall. Don’t use the screws to draw a
white wire in the cable functions as a switch leg, tape it
terminals. When all connections are
device to a box because the device may not lie
black to show that it functions as a hot wire.
tight, tuck the wires into the box and
flat, and it’s easy to strip the screw holes in a
screw the switch to the box.
plastic box. Using a cordless drill/driver is a lot
faster than using a screwdriver, but use a light
Wiring a “switch loop”:
trigger finger on the torque clutch of the driver
the Modern Method
The 2011 NEC requires that
there be a neutral in every
to avoid striping the screw head or snapping off
zzzzzz
switch box because some
the screw.
electronic timer switches and
Ground
a single-pole switch with a “switch loop.”
other energy-saving controls
This section shows two ways of wiring a switch
Neutral available need a neutral. Thus, if you
for electronic
when an outlet or fixture box is closer to the
switch
want to use a switch-loop
power source than to the switch box, commonly
approach, you must use
called a switch loop. The first way to wire a
three-conductor (“3-wire”)
cable, connect the neutral at
switch loop, shown in the drawing above right,
the power source, and then
can probably be found in 90 percent of homes
cap off the neutral in the
but has been superseded by changes in the elec-
switch box. Because 3-wire
trical code. The second way to wire a switch
cable has both a black and red
loop, shown in the drawing at right, conforms
conductor, there is no need to
to the 2011 NEC and should be used for new
re-identify the white
installations.
&nbs
p; conductor as hot, as was done
in the old method, above.
electrical Wiring
305
dimmer leads
It’s critical which circuit wires you attach to
dimmer leads. so during the rough-in stage, dis-
tinguish which wire is the switch leg and which
is the incoming hot wire for each single-pole
dimmer that you install. to distinguish these
wires, many electricians wrap the wires together
and bend back the switch leg wire. typically, the
red dimmer lead attaches to the switch leg wire,
and the black dimmer lead attaches to the
incoming hot wire. or slip a short sleeve of cable
sheathing back onto the stripped wires and use a
1. Dimmer specifics vary from one
felt-tipped marker to label what each wire does.
manufacturer to the next. read
installation instructions beforehand:
see the photo on the bottom of p. 291.
It’s critical which circuit wires you
attach to dimmer leads.
the historical method. Before the code
2. Prepare stranded dimmer leads by
changed it was common to run a single length of
twisting them to compact them,
12/2 or 14/2 cable as a switch loop. This means
before attaching them to solidwire
bringing the power down from the fixture to and
circuit wires.
through the switch and then back up to the fix-
ture. As such, the black wire in the 12/2 or 14/2
switch loop functions as the incoming hot wire,
and the normally neutral white wire acts to
return the power to the fixture. Here, the white
wire is actually a hot wire and is marked to iden-
tify it as such.
At the outlet or fixture box, splice all the
grounds together. Attach the source neutral wire
to the fixture neutral wire. Attach the source hot
wire to the white wire (taped black) of the switch
loop. Last, connect the switch loop black wire to
the black fixture wire (see p. 314 for more).
3. Cap any lead you won’t connect.
4. Attach the ground wire, then connect the red lead to
Note: Here, for convenience, we bend the rule
the switch.
of using a white wire only as a neutral wire and
instead wind black tape on each end of the white
P r O t I P
wire to show that—in this case—the white wire is
being used as a hot wire.
unless manufacturer’s
At the switch, start by stripping and looping
instructions say otherwise,
the wire ends in the switch loop. Next, tape the
Renovation 4th Edition Page 71