Here are the latest short answers to questions posted on our Web site. In our discussion, we will cover topics from Secs. 210-19(d), 220-3(b)(9), 240-3(e), 345-3, 346-3, 347-14, 348-5, 430-6(a), 430-22(a), 430-24, 430-32, 525-1, and 525-13(d); Arts. 525 and 820; and Tables 430-147, 430-148, and 150 of the National Electrical Code (NEC).
Q. How many receptacles does the NEC allow downstream from a feed-through GFCI receptacle?
A. There's no limit on the number of receptacles fed from a feed-through GFCI receptacle; however, the NEC does limit the number of receptacles on a circuit in occupancies other than dwelling units. The maximum number of receptacles permitted on a commercial or industrial circuit is based on the 180VA per outlet rule and the VA rating of the circuit [Sec. 220-3(b)(9)].
Q. Can you use No. 14 wire for receptacle taps from a 20A circuit?
A. No. Sec. 240-3(e) points to Sec. 210-19(d) for rules on branch circuit tap conductors. Exception No. 1(c) to Sec. 210-19(d) permits No. 14 wiretaps for other than receptacle outlets.
Q. When sizing conductors and short-circuit protection for motors, should we use the motor nameplate current or the Table FLC as listed in the Code?
A. According to Sec. 430-6(a), you are to use the FLC values given in Table 430-147, 430-148, or 430-150 to determine the ampacity of conductors or ampere ratings of switches, branch circuit, short circuit, and ground-fault protection instead of the actual current rating marked on the motor nameplate. See Secs. 430-22(a) and 430-24.
Note: You shall use the motor nameplate current rating where separate motor overload protection is provided to comply with Sec. 430-32.
Q. How many consecutive feet of rigid nonmetallic conduit can you run before you need a junction box?
A. There's no limit. The only limitations would be the length of the conductors with no more than the equivalent of four quarter bends (360ø total) between pull points (Sec. 347-14).
Q. When using nonmetallic sheath cable for temporary wiring at carnivals, does Art. 305 or 525 apply? Are splices and joints required in junction boxes?
A. Sec. 525-1 states that Art. 525 covers the installation of portable wiring and equipment for carnivals, a circus, exhibitions, fairs, traveling attractions, and similar functions. Sec. 525-13(d) specifies, "Flexible cords or cables shall be continuous without splice or tap between boxes or fittings."
Q. Is it a Code violation for armored or metal-clad cable to be in contact with copper water piping?
A. No. The Code doesn't prevent the contact of armored or metal-clad cables with copper water piping, but Secs. 345-3 (Rigid), 346-3 (IMC) and 348-5 (EMT) states that where practicable, contact between dissimilar metals shall be avoided to eliminate the possibility of galvanic action. Naturally, we would like to keep the metal armor of electrical wiring from making contact from copper water piping, but this is not a Code requirement.
Q. Does the NEC require you to use coaxial cable for security cameras within a raceway?
A. No. Chapter 8 is independent of other chapters in the Code, and there is no mention in Art. 820 requiring you to install coaxial cable within a raceway.