I recently installed a 4 pak meter base with room for 4- 200 amp main breakers on an existing building. I installed 1- 200 amp main for an existing 200 amp remote panel and 3- 100 amp mains for (future remote panels) for 3-future 1 bedroom apartments. The electrical inspector informed me that my mast wires (which were 500 mcm) were too small. He said that I had to size the conductors according to the maximum rated load of the buss inside the meter pak.(which was 600 amp max rated). I thought you had to size the feeder conductors according to the load not the size rating of the bussing. The future apartments are going to need approx 50 amps each and the existing 200 amp panel has a current calculated load of 125 amps. Please help me figure the correct size service entrance conductors to install in the 3" mast and weatherhead. Thank you.
Service Conductor sizing
- Thread starter dhobdey1
- Start date
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- Location
- Massachusetts
In my opinion the inspector forgot about 230.90(A) Exception No. 3. 
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
230.90(A)Ex 3
..." The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors provided the calculated load does not exceed the ampacity of the service conductors."
I am not sure which part of this the inspector is having issues with. It is common practice in our area.
..." The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors provided the calculated load does not exceed the ampacity of the service conductors."
I am not sure which part of this the inspector is having issues with. It is common practice in our area.
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