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Renovation 4th Edition

Page 67

by Michael Litchfield


  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-r />
  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

 

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