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Re: CQD answer published Thursday, January 4, 2018 -
I find this web site something like an opioid, I can’t stop. I understand the questioner didn’t specify a 110 volt or 220 volt feeder but I have found electricians like to serve the outbuildings 220 volt feeder using triplex, as our local utility serves our residents. The utility uses the bare messenger in the triplex as the grounded conductor and there isn’t an equipment grounding conductor. Obviously a 220 volt feeder should use quadruplex to provide for the insulated grounded conductor and the bare messenger as the equipment grounding conductor.
Hey Dave thanks for your question, we are glad to hear that reading CQD is habit forming, in a good way. Single conductors in Table 310.104(A) are only allowed to be used as a recognized wiring method as stated in 300.3. Table 310.104 (A) includes various types of insulated conductors as that term is defined in Article 100. Triplex and quadruplex cables are covered by Article 396 as messenger supported wiring but the products typically used by electric utilities are not marked as required by 310.120.
A new definition in 396.2 for insulated conductor in the 2017 NEC indicates that "conductors encased in a polymeric material that has been evaluated for the applied nominal voltage" (triplex and quadruplex) are considered insulated if used for service conductors. They are not yet allowed for feeders and branch circuits. You are correct that an equipment grounding conductor needs to be included as stated in 250.32(B)(1).
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