National Electrical Installation Standards

Standards as High as Your Own

Friday, November 8, 2019


What is the smallest conductor that can be paralleled? If utility conductors enter a building underground and once entering the building proceed more than 20' to the main disconnect of the building are they in violation of the code?

Charles Tucker


Hey Charles thanks for your question. The smallest conductor that can be connected in parallel is a 1/0 as stated in 310.10(H) unless one of the exceptions applies. If the utility owns the conductors the NEC does not apply as stated in 90.2(B)(5). If the conductors are customer owned then the disconnecting means must be located nearest the entrance point of the service conductors as stated in 230.70(A)(1).

No dimension is given for "nearest" and if the service equipment is large such as a unit substation and cannot be located directly where the conductors enter the building it might be allowed. It is up to the AHJ to make that decision.

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