sticking.
all newly installed devices must be grounded. Code allows you to replace an existing two-prong
receptacle or to replace a nongrounded box that has become damaged. however, if you install a new
three-prong receptacle, it must be grounded. the only exception: You can install a three-prong receptacle
into an ungrounded box if that new device is a gFCI receptacle. If you extend a circuit, the entire circuit
must be upgraded to current code.
In new rough-in work, cable must be supported within 8 in. of a single-gang box without clamps
and within 12 in. of any other box and every 41⁄2 ft.
Begin the layout by consulting wiring plans, then walking
A laser level quickly sets box heights
the room and marking box locations.
around a room.
Have materials on hand when it’s time to start installing
boxes. Electricians often walk from room to room,
dropping a box wherever floor plans indicate.
electrical Wiring
287
Here, a laser beam indicates the
laying ouT The job
center of a box. The notations on the
edge of the stud indicate that this
With electrical plans in hand, walk each room
will be a GfCI receptacle. More
and mark box locations for receptacles, switches,
commonly, electricians measure
and light fixtures. Each device must be mounted
box heights from the bottom or
to a box that houses its wiring connections. The
top of a box.
only exceptions are devices that come with an
integral box, such as bath fans, recessed light
cans, and under-cabinet light fixtures.
Mark receptacle and switch locations on the
walls first. Then mark ceiling fixtures. If studs
Snap a chalkline to indicate box
and joists are exposed, use a brightly colored
heights if there’s no laser on hand.
crayon. If there are finish surfaces, use a pencil
to mark walls at a height where you can see the
notations easily—these marks will be painted over
later. Near each switch box, draw a letter or num-
ber to indicate which fixture the switch controls.
Once you’ve roughly located boxes on the
walls, use a laser level to set exact box heights for
each type of box.
Use the laser to indicate the tops or bottoms of
the boxes. Many electricians prefer to determine
level with the laser and snap a chalkline at that
height so they can move the laser to another room.
To locate ceiling fixtures, mark them on the
floor and use a plumb laser to transfer that mark
up to the ceiling. This may seem counterintuitive,
but it will save you a lot of time. Floors are flat,
almost always the same size and shape as the
ceilings above, and—perhaps most important—
. . . then use a plumb laser to transfer
those markings to the ceiling.
Center your hole saw
on each ceiling mark.
Many electricians prefer to mark ceilingfixture centers
on the floor . . .
288 Chapter 11
for convenience and speed, use a hammer length to
establish the height of work boxes. It’s close to the
standard height of 12 in.
rouGh-In reCaP: box locations
Whatever heights you choose to set outlets and switches, be consistent.
Code requires that no point along a wall may be more than 6 ft. from an outlet.
set the bottom of wall outlets 12 in. to 15 in. above the finished floor surface—or
18 in. above the finished floor surface if someone in the house has mobility issues.
place the top of switch boxes at 48 in., and they will line up with drywall seams
(if sheets run horizontally), thus reducing the drywall cuts you must make.
In kitchens and bathrooms, place the bottom of countertop receptacles 42 in.
above the finished floor surface. this height ensures that each receptacle will clear
the combined height of a standard countertop (36 in.) and the height of a backsplash
(4 in.), with 2 in. extra to accommodate cover plates. If you are unsure of counter
details, set the bottom of the box at 45 in.
accessible and easy to mark. In complex rooms,
such as kitchens, draw cabinet and island out-
lines onto the floor as well. Those outlines will
help you fine-tune ceiling light positions to opti-
mally illuminate work areas.
insTalling neW Work boxes
In this section, we’ll assume that framing mem-
bers are exposed and that boxes will be attached
directly to them. Once you’ve used your plans to
locate receptacle, switch, and light fixture boxes
To install an adjustable box, press the
nailon boxes cannot be adjusted for
on walls and ceilings, installing them is pretty
bracket flush against the stud edge
depth once installed, so use the depth
straightforward. Local electrical codes will dic-
and screw it down. The tiny silver
gauge on the side to ensure that box
tate box capacity and composition.
screw in the edge of the box is the
edges will be flush to finish surfaces.
depthadjusting screw.
Installing wall boxes. In residences, 18-cu.-in.
single-gang PVC plastic boxes are by far the most
Boxes with integral brackets have
common. They’re large enough for a single outlet
small points at top and bottom that
or a single switch and two cables. Otherwise, use
sink into the stud. A mud ring will
a 22.5-cu.-in. single-gang box or a four-square
bring the box flush to the finish wall.
box with a plaster ring.
Set each box to the correct height—as sum-
marized in the recap above—then set box depth
so that its edge will be flush to the finish surface.
If you use adjustable boxes, simply screw them to
a stud. To adjust the box depth, turn the adjust-
ing screw. Side-nailing boxes typically have scales
(graduated depth gauges) on the side. If not, use
To provide solid support for
a scrap of finish material (such as 1⁄2-in. drywall)
multigang boxes, first install an
as a depth gauge. Metal boxes frequently have
adjustable box bracket that spans the
brackets that mount the box flush to a stud edge;
distance between studs or use
blocking behind the box.
after the box is wired, add a mud ring (plaster
ring) to bring the box flush to the finish surface.
Multiple-gang boxes mount to studs in the
same way. But if plans locate the box away from
studs or a multigang box is particularly wide, nail
blocking between the studs or install an adjust-
able box bracket and screw the box to it. (The
electrical Wiring
289
Knockouts on metal boxes require a bit more force, so jab
them with a stout pair of needlenose pliers.
Once the knockout is loose, remove it using pliers.
Use a screwdriver to remove a
plasticbox knockout.
/> bracket is sometimes called a screw gun bracket
Installing ceiling boxes. Boxes for ceiling lights
because a screw gun is typically used to mount it
are most often 4-in. octagonal or round boxes or
and to attach boxes to it.) The more securely a
recessed light fixtures with integrated junction
P r O t I P
box is supported, the more secure the electrical
boxes. Setting ceiling boxes in new work is simi-
connections will be.
lar to setting wall boxes, with the added concern
that the ceiling box be strong enough to support
locating ceiling fixtures
removing knockouts. Once you’ve mounted
can be a literal pain in the neck.
the fixture. Many electricians prefer to use metal
boxes, you’ll need to remove the appropriate num-
it’s usually smart to determine
boxes for ceiling fixtures anyway. Ceiling fans
ber of box knockouts and install cable connectors
the approximate position of a
require fan-rated boxes.
(clamps). Single-gang, new-construction plastic
ceiling fixture on the floor or
In many cases, you’ll need to reposition the
boxes don’t need clamps: Simply strike a screw-
over a counter, then use a plumb
box to avoid obstacles or line it up with other fix-
driver handle with the heel of your hand to drive
bob or a laser to transfer the
tures, but it’s quick work if the box has an adjust-
out the knockout. To remove a metal-box knock-
location up to the ceiling.
able bar hanger. To install a recessed can, for
out, jab it with the nose of needle-nose pliers to
example, extend the two bar hangers to adjacent
loosen it, then use the pliers’ jaws to twist it free.
ceiling joists. Then screw or nail the hangers to
When the can height is where you want Then slide the can to finetune its
Use blocking to get the box in just the for box placement midway between
it, fasten its hanger bars to the joists.
position. Tighten the screws to lock it right spot.
joists, use an adjustable bar hanger.
in place.
Screw a metal box to the bar
hanger. Make sure the box
Alternately, you can nail
edge will be flush to the
2x4 blocking between
finish ceiling.
joists.
290 Chapter 11
the joists. Slide the can along the hangers until
P r O t I P
its opening (the light well) is where you want it,
and then tighten the setscrews on the side.
drilled holes don’t need to be
To install a 4-in. box, simply nail or screw it to
perfectly aligned, but the closer
the side of a joist. If you need to install it slightly
they line up, the easier it is to
away from a joist, first nail 2x blocking to the joist,
pull cable. some electricians use
then attach the box to the blocking. Remember:
a laser to line up drill holes.
The box edge must be flush to finish surfaces.
To install a 4-in. box between joists, screw an
adjustable hanger bar to the joists, then attach
the box to it. Alternately, you can insert 2x block-
ing between the joists and screw the box to it.
running eleCTriCal Cable
When drilling for cable runs, rest the
drill on your thigh. This method eases
Once boxes are in place, you’re ready to run cable
drilling and places holes at a
to each of them. It’s rather like connecting dots
convenient height above box
locations. Watch for kickback if
with a pencil line.
the bit binds—it can break a hand
drilling for cable. To prevent screws or nails
or an arm. Wear goggles when
from puncturing cables, drill in the middle of
drilling.
studs or joists whenever possible. If the holes
you drill are less than 11⁄4 in. from the edge of
framing members, you must install steel nail-
protection plates (see p. 292). Always wear eye
protection when drilling.
identifying Cable runs
Drill for cables running horizontally (through
studs) first. It doesn’t matter whether you start
To avoid confusion when it’s time to wire devices, identify incoming cables. use
drilling at the outlet box closest to the panel or at
felt-tip markers to write on the cable sheathing, or write on masking tape wrapped
the last outlet on the circuit. Just be methodical:
on grouped wires.
Drill holes in one direction as you go from box to
box. However, if you’re drilling for an appliance
Cables running from the panel board to an outlet should be marked “source,”
that has a dedicated circuit—and thus only one
“from source,” or “upstream.” if you’re wiring gfCi receptacles, these incoming
outlet—it’s usually less work to drill a hole
cable wires attach to gfCi terminals marked “line.” Cables running on to the next
through a top or bottom plate and then run cable
outlet (away from the power source) are denoted “next outlet” or “downstream”;
through the attic or basement instead of drilling
they attach to gfCi terminals marked “load.”
through numerous studs to reach the outlet.
double- or triple-gang boxes will have a lot of cables entering, so make the cable
If possible, drill holes thigh high. Partially rest
descriptions specific: “switch leg to ceiling fixture,” “3-way switch #2,” and so on.
the drill on your thigh so your arms won’t get as
tired. This method also helps you drill holes that
are roughly the same height—making cable-
pulling much easier. Moreover, when you drill
To speed trimout of this multipleswitch
about 1 ft. above a box, you have enough room to
box, the electrician wrote the fixture each
bend the cable and staple it near the box without
switchleg controls onto slugs of cable
crimping the cable and damaging the insulation.
sheathing.
For most drilling, use a 6-in., 3⁄4-in.-dia. auger
bit. Use an 18-in. bit to drill lumber nailed
together around windows, doorways, and the
like. Using an 18-in. bit is also safer because it
enables you to drill through top plates without
standing on a ladder. Standing on the floor is a
big advantage, as the reaction torque from a
heavy duty drill can throw you off a ladder if a bit
binds up.
Pulling cable. For greatest efficiency, install
cable in two steps: (1) Pull cable between outlets,
leaving roughly 10 in. extra beyond each box for
splices, and (2) retrace your steps, stapling cable
to framing and installing nail-protection plates if
electrical Wiring
291
P r O t I P
Cables should be attached to
framing at least every 54 in.
Cables must also be stapled
within 8 in. of a single-gang box
; with no clamps, or within 12 in.
of any other box.
S a f e t y a l e r t
Place a wire wheel near the beginning or end of
each circuit.
Cables should not be stacked
tightly under single staples—it’s
Staple snugly but not tightly enough to squeeze the cable
called bundling—for a distance
sheathing. note the cable spooler on the floor in the
of more than 2 ft. bundling may
background.
cause wires to overheat, thus
reducing the amperage they can
carry safely. instead, use a cable
standoff to hold cables loosely
apart in the middle of the stud
so they can’t get pierced by
drywall screws.
for cables within 11⁄4 in. of a stud
edge, install steel plate to protect
them from being punctured by a
nail or screw.
When bundling two or more cables, use standoffs.
the last box and pull cables toward the panel.
When they reach the first boxes of several cir-
cuits, they will move the wire reels to those loca-
tions. From there, they feed, say, three cables
down to a helper in the crawlspace. The helper
can pull all the cables toward the panel at the
same time. This method is much faster than pull-
they’re required. As with drilling, it doesn’t mat-
P r O t I P
ing single cables three different times.
ter whether you start pulling cable from the first
Staple cable along stud centers to prevent nail
box of a circuit or from the last box. If there are
The neC requires at least 6 in.
or screw punctures. It’s acceptable to stack two
several circuits in a room, start at one end and
of “free” wire in a box, and at
cables under one staple, but use standoffs to fas-
proceed along each circuit, pulling cable until all
least 3 in. of it must extend
ten three or more cables traveling along the same
the boxes are wired. Don’t jump around: You may
beyond the front of the box. but
path. (Multigang boxes are fed by multiple
seasoned electricians usually
become confused and miss a box.
cables, for example.) Standoffs and ties bundle
leave more wire sticking out—
In new construction, electricians usually place cables loosely to prevent heat buildup. As you
about 6 in. is ideal, which means
several wire reels by the panel and pull cables
Renovation 4th Edition Page 68