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Friday, October 7, 2016
Question:
Suppose the utility company runs #8 AWG wire from the transformer to my house and my service needs to be 100 amps. The feeder need to be #4, but according to section 215.2(A)(4) the feeder can be #8 and I comply with NEC rules
Jaime Garcia
A
Answer:
Hey Jaime thanks for your question. What the utility does is not covered by the NEC as stated in 90.2(B)(5). Keep in mind the service drop conductors are usually in free air and the utility has many years of experience in sizing conductors without significant problems.
Service conductors for a 100 ampere dwelling service can be sized using 310.15(B)(7) if they meet all the conditions. For a 100 ampere service, 4 AWG conductors would be suitable because they are at least 83% of 100 using Table 310.15(B)(16) assuming no additional factors. Section 215.2(A)(4) was deleted in the 2014 NEC but it was based on customer owned service conductors, not the utility owned conductors.