9 Common Wiring Mistakes and Code Violations
Total Page：16
File Type：pdf, Size：1020Kb
Common Wiring Mistakes and Code Violations Some are illegal, some are dangerous, 9and some are both—but all are simple to avoid BY JOSEPH FRATELLO hether to save time or money, 1. Protect wiring lots of nonelectricians do electrical work. This is espe- from nails cially true during the rough- and screws. Win phase of new construction: drilling holes, running wire, and nailing up boxes. Remod- elers take on tasks as seemingly mundane as installing a new light fixture. As an electrical PROBLEM There must be a 11⁄4-in. contractor, I’ve hired many union and non- clearance from the edge of a wood-framing union electricians over the years, and most member to any wire to keep drywall screws were horribly misinformed about the elec- and long trim nails from puncturing the trical trade and the building codes. If pro- insulation and causing a short. fessionals have a hard time keeping up with important details, I imagine that carpenters SOLUTION Wiring and do-it-yourselfers are going to have a passing through holes harder time. Before tackling electrical work, closer than 11⁄4 in. to you should be aware of a few things. the framing face must First, check with your local or state build- be protected with nail ing department to see what licenses or per- plates. Several runs of mits are required. The National Electrical wiring can be corralled Code dictates minimum requirements for with inexpensive safe electrical installation, but local building Cable Stackers, which authorities often impose their own codes. maintain the distance mandated by code. Second, in some areas, homeowners are not allowed to perform electrical work unless they are licensed or certified electricians. It’s that make electrical work code-compliant cable (often referred to as Romex), you must a good idea to check with your local or state and safe. If you’re ready to go to work, keep maintain a 11⁄4-in. clearance from the edge of building authorities before doing any work. reading. The following is a list of mistakes to a stud to protect the wire from errant drywall In many instances, a homeowner can hire a avoid during electrical installations. screws or long trim nails. It’s hard enough to licensed electrician who can pull a permit fix the damage properly, but the risk that the and supervise any rough wiring that the Romex needs its jacket whole damaged wire could remain unnoticed and homeowner might do. Potential liabilities are On more than one occasion, I have seen wires start a fire inside the wall cavity is worse. involved (sidebar p. 79), but various resources punctured by a long fastener that missed its What can you do if you are working on a (p. 80) clearly explain the correct methods mark. When using nonmetallic sheathed 2x4 wall and need to bring eight wires into a 76 FINE HOMEBUILDING COPYRIGHT 2007 by The Taunton Press, Inc. Copying and distribution of this article is not permitted. box? Cable Stackers, a 3M product (www 2. Don’t mix line- .3m.com), hold up to eight wires and make it easy to position them correctly. voltage and low- In some circumstances, you have no voltage wires. choice but to bore a hole closer than 11⁄4 in. from a framing edge. There, you must install 1 a steel nail plate, either ⁄16 in. thick or UL- PROBLEM Parallel runs of line- and low- listed for that purpose, to protect the wires voltage wires cause interference in electronics from damage. and/or communication, such as TVs and telephones. Also, any uninsulated contact Keep low and line voltage apart between low- and line-voltage wires in a box I often see two-gang boxes installed with can damage equipment or cause a fire. a cable or phone jack in one half and a 120v outlet in the other. If an exposed conductor of a low-voltage wire comes in contact with SOLUTION Maintain a 120v, the higher voltage can damage what- minimum of 6 in. between ever is at the end of the low-voltage wire. parallel runs, and you won’t A solid connection between the exposed have to shout over the phone. low-voltage wire and a 120v wire also can Don’t bring low voltage cause the insulation to melt and start a fire. and line voltage together in You can’t run communication wires (phone, the same box. Instead, use cable, or other low-voltage wires) into a separate boxes or a box that box occupied by 120v or higher unless the has an approved divider. communication wire or the box is rated for that use. A similar situation concerns proximity. control boards for the heating and air condi- The problem is made worse when you add Phones, cable boxes, computers, and tele- tioning. Although many people blamed the dimmers to a crowded switch box. Dim- visions all are susceptible to interference, a carpenter for the mishap, the HVAC contrac- mers generate a substantial amount of heat condition made worse when line voltage tor had violated the code and was responsible on their own; combined with the heat poten- and low voltage are run parallel through the for the damage. The HVAC mechanic who tial of the wires, a bad situation can be made same hole. The extent of the interference ran the wire lost his job. worse. I’ve never seen a box catch fire as a depends on the quality of wire you use and result of being overfilled with wires, but I the amount of current passing through the Overcrowded boxes can start a fire have seen a few melted dimmers. The next line-voltage wires. When I run low-voltage When too many wires, outlets, or switches time you try to cram eight wires into a single- wires parallel to line-voltage wires, I fasten are crammed into a box, the heat generated gang box, think about who would be respon- the low-voltage wires at least 6 in. away from doesn’t have enough airspace to dissipate and sible if the box caught fire. the line voltage. in turn can melt wire insulation and has the The easiest way to learn how to calculate When you run line- and low-voltage wires potential to cause a fire. the maximum wire fill of any box is to use in the same hole, you risk having the line voltage cross over into the low volt- age, which can also cause a fire. One PROBLEM unfortunate incident I witnessed could 3. Don’t stuff too Overcrowded have been easily avoided by keeping many wires boxes can the wires separated. overheat, cause A carpenter was adding extra brac- into a switch or insulation to melt, ing for floor joists in the basement outlet box. and potentially of a house we had wired. As he was cause a fire. nailing, he didn’t look to see what was on the other side of the joist. He drove a 16d nail straight through a 120v electrical line and into a thermostat wire that the HVAC SOLUTION If contractor had run through the the box is too same hole after the rough wiring small, use a larger was complete. When the 120v crossed into box and a plate the thermostat wire, it destroyed the entire known as a plaster home-automation system, along with all the (or mud) ring. www.finehomebuilding.com 77 COPYRIGHT 2007 by The Taunton Press, Inc. Copying and distribution of this article is not permitted. PROBLEM Because of SOLUTION A splice box and a minimum 4. Use a splice box compatibility issues related to of 3 ft. of new wiring should connect a new safe operating temperatures, new light fixture to a circuit wired before 1987. when installing fixtures can overload an older It’s the preferable alternative to rewiring wiring system and cause a fire if the entire circuit. Here’s a good way to a new fixture improperly installed. determine the wiring’s age: Insulation to old wire. jackets made after 1987 are stamped with the date of manufacture (inset photo right); those made prior to 1987 have no date. the NEC Handbook, which has a section or has 60°C wiring, consult a qualified elec- or kneewall space), you can remove the wire dedicated to this subject; you also can read trician”? Wire is rated for the safe operating from the existing fixture box and install it “More Wires Need Bigger Boxes” (FHB temperature of the conductors. Newer light in a junction box. You can then splice on a #144 or FineHomebuilding.com). fixtures are made with 90°C wires, which new piece of wire (make sure it is the same means the wire inside the fixture is rated to wire gauge) and run the new piece from the Read labels before installing new operate safely at temperatures up to 90°C. junction box back to the fixture box. You light fixtures to old wires Problems occur when you connect the new should have at least 3 ft. of new wire from The last time you put up a new light fixture, fixture to old wires in the house. Most homes the splice box to the fixture box. By installing did you notice the little tag on the fixture that built before 1987 were wired with 60°C con- the new wire in the fixture box, you will be says, “If your house was built prior to 1987 ductors; the new fixture can create heat that code-compliant and not have to worry that can overpower the older wires’ capacity and the new light will cause a fire.