The generator being installed is a 20kw, @83amps, with a 100amp breaker on the generator. The ats is service rated 200amp & the existing service is 200amps. Wanted to use table 310.15b7 which would be (al 2/2/2/w ground ser)from the generator to the switch. The problem I think I see is the code says to use this table if the conductors carry 100% of the load. I'm locking out misc loads such as the electric range,washer & dryer. So, with these loads locked out is this carrying 100% of the load or not???
Genset feeder conductor sizing
- Thread starter Bam
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JoeStillman
Senior Member
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- West Chester, PA
Between the generator and ATS, #2 SER should be ok, as long as you ensure that the connected load is within the generator capacity. If the connected load exceeds the generator capacity, you will stall the engine before you blow up the cable.
Also, the cable is protected at the point where it recieves its supply (the generator output breaker.)
Also, the cable is protected at the point where it recieves its supply (the generator output breaker.)
Lots of possible red flags.
IMHO, you can not use 310.15(B)(7) as it is limited to conductors carrying "all loads ...associated with the dwelling". With the generator supplying only selected loads, you do not have the same diversity as a whole house feeder.
Secondly, at best #2 AL is a 90 amp conductor and SER might even be a 75 amp conductor. In either event, not permissible on a 100 amp breaker.
also, your SER does not happen to run in underground conduit to your generator does it ?
IMHO, you can not use 310.15(B)(7) as it is limited to conductors carrying "all loads ...associated with the dwelling". With the generator supplying only selected loads, you do not have the same diversity as a whole house feeder.
Secondly, at best #2 AL is a 90 amp conductor and SER might even be a 75 amp conductor. In either event, not permissible on a 100 amp breaker.
also, your SER does not happen to run in underground conduit to your generator does it ?
Thanks for the responses, I knew the key words in the code (310.16.B.7) were "all loads" and I still think it's left up to the inspectors interpertation. To be on the safe side I will use the next larger size (al 1/1/1 SEU) from table 310.15.B.16, until I have this discussion with the inspector. Thanks again. & no the cable is not underground.
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