Stumped by the Code? September 2010

Stumped by the Code? September 2010

Your most pressing National Electrical Code (NEC) questions answered

All questions and answers are based on the 2008 NEC.

Q. What are the grounding requirements for a separate building supplied with a feeder?

A. For buildings or structures supplied by a feeder, each building/structure’s disconnect must be connected to an electrode of a type identified in 250.52 [250.32(A)]. The grounding of the building/structure disconnecting means to the earth is intended to help in limiting induced voltages on the metal parts from nearby lightning strikes [250.4(A)(1)]. The Code prohibits the use of the earth to serve as an effective ground-fault current path [250.4(A)(5) and 250.4(B)(4)].

Exception: A grounding electrode isn’t required where the building/structure is served with a 2-wire, 3-wire, or 4-wire multiwire branch circuit.

To quickly clear a ground fault and remove dangerous voltage from metal parts, the building/structure disconnecting means must be connected to the circuit equipment grounding conductor of a type described in 250.118. If the supply circuit equipment grounding conductor is of the wire type, it must be sized in accordance with 250.122, based on the rating of the overcurrent device [250.32(B)], as shown in Fig. 1.

Caution: To prevent dangerous objectionable neutral current from flowing onto metal parts [250.6(A)], the supply circuit neutral conductor isn’t permitted to be connected to the remote building/structure disconnecting means [250.142(B)].

Q. Is it acceptable to install a GFCI receptacle in a dwelling unit bathroom and feed from the load side of the GFCI receptacle to a duplex receptacle in a second bathroom?

A. Yes. One 20A, 120V branch circuit must be provided for the receptacle outlets required by 210.52(D) for a dwelling unit bathroom. This 20A bathroom receptacle circuit must not serve any other outlet, such as bathroom lighting outlets or receptacles in other rooms. However, it can feed the receptacle outlets in multiple bathrooms, which can be fed from the load side of a GFCI receptacle from the first bathroom [210.8(A)(1) and 210.11(C)(3)], as shown in Fig. 2.

Note: A 15A, 125V receptacle is rated for 20A feed-through, so it can be used for this purpose [210.21(B)(3)].

Exception: A single 20A, 120V branch circuit is permitted to supply all of the outlets in a single bathroom, as long as no single load fastened in place is rated more than 10A [210.23(A)].

Q. Does the Code requirement for bonding of pool water in 680.26(C) apply to above ground nonconductive pools?

A. Yes, if it is a permanently installed pool. The requirement for bonding of pool water in 680.26(C) states that pool water must have an electrical connection to one or more of the bonded parts described in 680.26(B). If none of the bonded parts is in direct connection with the pool water, the pool water must be in direct contact with an approved corrosion-resistant conductive surface that exposes not less than 9 sq in. of surface area to the pool water at all times. The conductive surface should be located where it’s not exposed to physical damage or dislodgement during usual pool activities, and it must be bonded in accordance with 680.26(B).

Q. Are 20A rated duplex receptacles required when installed on a 20A, 120V multi-outlet branch circuit?

A. No. If connected to a branch circuit that supplies two or more receptacles, receptacles must have an ampere rating in accordance with the values listed in Table 210.21(B)(3), which allows the use of either 15A or 20A rated receptacles on a 20A branch circuit (Table).

Q. What are the GFCI protection requirements for vending machines?

A. Cord- and plug-connected vending machines must include a GFCI as an integral part of the attachment plug, or within 12 in. of the attachment plug. Older machines that are not so equipped must be connected to a GFCI-protected outlet [422.51]. The term “vending machine” means a self-service device that dispenses products or merchandise and requires coin, paper currency, token, card, key, or receipt of payment by other means. Because electric vending machines are often located in damp or wet locations in public places and are used by people standing on the ground, reliance on an equipment grounding conductor for protection against electrocution is insufficient.

Q. Can conductors be spliced inside a raceway?

A. No. Conductors in raceways must be continuous between all points of the system. This means splices must not be made in raceways, except as permitted for non-circular raceways such as wireways, as noted in Secs. 376.56, 378.56, 384.56, 386.56, or 388.56. [300.13(A)].

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.