National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, August 21, 2018

Question:

Re: CQD answer published Wednesday, August 10, 2018 - Temporary Feeder 2

Aerial cable such as Triplex, is not listed or labeled by a National Recognized Testing Laboratory (NRTL). It may be used up to the service drop since the NEC does not incorporate that part of the service system owned by the utility. From there on, Listed material must be used unless specifically allowed or sanctioned by other means.

I've heard of Four-Plex cable that allows for the insulated neutral wire (grounded conductor) to be carried with the messenger cable, normally used for the grounding conductor. However, I've yet to come across this method of wiring being described in the NEC for use.

Best Regards, Nick Abbatiello

A

Answer:

Hey Nick thanks for your comment. 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 those products typically used by electric utilities are not listed; or 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.

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