I have a 150 amp main electrical panel. I had electrician install an automatic transfer switch for a whole house generator and I am unaware of the original gauge wire used before the install. After the ATS was installed I noticed the electrician used copper SER 1 gauge conductors with 3 gauge ground wire to connect the meter to the ATS and then used the same size cable to connect the ATS to the original electric panel. I saw one of the NEC charts stating that the 75C rating for SER 1 gauge copper wire is only 130 amps. Will this wire be ok with this installation/150 amp main breaker? Must the wire be replaced with 1/0 gauge or does the 150 amp panel now become a 130 amp panel?

  • I believe feeder(what you have) and circuit gauge sizes are different. According to this chart you have the right size. learnmetrics.com/electrical-feeder-size-chart. Will let the ones who know better answer.
    – crip659
    Nov 17, 2023 at 22:13
  • I meant feeder sizes are allowed more amperage, than regular circuits.
    – crip659
    Nov 17, 2023 at 23:19

1 Answer 1


Services to homes follow their own table

Services and feeders feeding an entire home ("dwelling unit" in Code-ese) use Table 310.12(A) in the NEC, which permits a 150A service to be run using 1AWG copper wire. (If you're wondering how that table is derived, the basic rule is that the ampacity of the service wire can be 83% of the service's "nameplate" ampacity in this case.)

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