Service Amperage Rating

[Tom Rees]

I am a little confused as I have read conflicting statements about this. I inspected a large (8000 sq. ft.) new home. At the exterior service panel were two double pole 200 Amp breakers each connected to its own distribution panel in basement. Is this a 200 or 400 Amp service?:D

[Jerry Peck]

At the exterior service panel were two double pole 200 Amp breakers each connected to its own distribution panel in basement. Is this a 200 or 400 Amp service?:D

Yes. :D

It would depend on the size of the service entrance conductors, and it they are sized to 400 amps, then it would be a 400 amp service, however, if they were sized to 300 amps (which is allowed), the the service size is 300 amps. If the service entrance conductors are bus bars, then it would depend on the rating of the bus bars. If either the service entrance or the bus bars are rated over 400 amp, then the limitation would be the 2-200 amp mains, or 400 amps.

Multiple mains cannot just be added together, however, with a little determination you can usually (but not always) determine what is the limiting factor and the smallest limiting factor would be the service rating.

[Tom Rees]

Thanks Jerry. It was what I thought but some people put wrong info in my head.:D