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September 18, 2008 A Penton Media Publication Vol. VI No. 18

250. 32 Buildings or Structures Supplied By Feeder or Branch Circuit

What's Wrong Here?

Code Q&A

Code Quiz

Rhode Island State Electrical Code

Call for Papers


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    Top 2008 Code Changes

    250. 32 Buildings or Structures Supplied By Feeder or Branch Circuit

    By Mike Holt
    The rule that permitted the re-grounding of the neutral conductor at separate buildings and structures was deleted.

    (B) Equipment Grounding Conductor. To quickly clear a fault and remove dangerous voltage from metal parts, the building disconnecting means shall be connected to the circuit equipment grounding conductor of a type described in 250.118. Where the supply circuit equipment grounding conductor is of the wire type, it shall be sized to 250.122, based on the rating of the supply circuit overcurrent device rating.

    Exception: For existing premises, when an equipment grounding conductor was not run to the building or structure disconnecting means, the building or structure disconnecting means can remain connected to the neutral conductor where there are no continuous metallic paths between buildings or structures, ground-fault protection of equipment isn't installed on the supply side of the circuit, and the neutral conductor is sized no smaller than the larger of:

    1. The maximum unbalanced neutral load in accordance with 220.61.
    2. The rating of the circuit overcurrent device, in accordance with 250.122.
    Caution: To prevent dangerous objectionable neutral current from flowing onto metal parts [250.6(A)], the supply circuit neutral conductor is not permitted to be connected to the remote building or structure disconnecting means [250.142(b)].

    In the 2005 NEC, 250.32(B)(2) permitted the neutral conductor to serve as the effective ground-fault current path. This rule was converted into an exception for existing premises. Using the neutral conductor to connect metal objects to the effective ground-fault current path is a dangerous practice, especially if the neutral becomes open.

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    Code Challenge
    What's Wrong Here?
    By Joe Tedesco
    Think you know how this installation violates the NEC? Visit EC&M's Web site to see the answer.

    Hint: D.C. exposure

    Code Q&A
    By Mike Holt
    Q. We have motors that are interlocked, preventing them from being on at the same time. Do we still have to add them up for service and feeder calculations?

    Visit EC&M's Web site to see the answer.

    Code Quiz
    By Steven Owen
    Q. When grounding the ferromagnetic envelope of skin effect-heating systems, what are the grounding requirements?

      1. Grounding is not required.
      2. Grounding one end only with an equipment-grounding conductor is required.
      3. Grounding both ends with an equipment-grounding conductor is required. Grounding any intermediate points in between the ends is also permitted.
      4. GFCI protection (Class C, 30mA trip) is required.

    Visit EC&M's Web site for the answer and explanation.

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    Code News Update
    Rhode Island State Electrical Code
    On June 19, 2008 the Rhode Island Building Code Standards Committee held a public hearing to hear testimony on the adoption of the State Electrical Code (SBC-5). The SBC-5 technical subcommittee recommended the adoption of the 2008 National Electrical Code (NEC) without any technical amendments. It was recommended that the existing administrative amendments to SBC-5 be retained. The Rhode Island Building Code Standards Committee accepted the technical subcommittee recommendation and voted 14-1 to adopt the 2008 NEC. The bill has been filed with the Secretary of State and became effective Aug. 1, 2008, with a mandatory date of Nov. 1, 2008.

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    Shows and Events

    Call for Papers

    The National Fire Protection Association (NFPA) is accepting proposals for educational presentations at its 2009 Conference & Expo to be held June 8-10 at McCormick Place in Chicago. The deadline is tomorrow (September 19, 2008), but you still have time to submit your proposal online or download a proposal form.

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