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#77085 04/20/01 09:52 AM
Joined: Apr 2001
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Pete Offline OP
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Built a metal building, with office inside with metal studs. No wood anywhere. Bldg & studs are grounded. Each receptacle has its own grounding lead. Our code enforcement inspector says each junction box must also have a grounding lug. Further, any rigid metal conduit with more than 3 load carrying conductors, conductors must be derated. So, if a 2" conduit has 4 conductors, the wire must be oversized. I'd appreciate comments.

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Joined: Nov 2000
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Pete,
250-148(a) requires the EGC to be connected to the box. Table 310-15(b)(2)(a) requires derating of conductors for more than 3 current carrying conductors. Remember that is you are using THHN you can use the 90°C ampacity for derating purposes.
Don(resqcapt19)


Don(resqcapt19)
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Tom Offline
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Pete,

Don's reply is right on the money. With THHN insulation in a dry location, you usually don't have a derating problem (at least in the smaller sizes) until you get to the 10th conductor.

Tom


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