Renovation 4th Edition

by Michael Litchfield

  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