310.12 - Sizing conductors downstream of ATS

[marmathsen]

Do the downstream conductors of an ATS serving the entire load of the house qualify for 83% sizing per 310.12?

In particular I'm thinking about the sense, control, and battery charge conductors that would not be included in the feeder supplied by the ATS. In a Generac transfer switch I'm looking at, the T1, N1, and N2 conductors are protected by (3) 240VAC 6.3A fuses which makes me think I CAN'T USE THE 83% ALLOWANCE.

Rob G - Seattle

 

[jaggedben]

I think you can still use it and those control items don't count as part of the dwelling load. But also, a feeder is never required to be larger than the service conductors are required to be under 310.12. So if the feeder was compliant before, it's still compliant. (And if it isn't compliant now, it wasn't before.)

Edit: actually since it's unclear if this is a retrofit or new construction, I'll put it this way: if the feeder could use 310.12 without the ATS present, it can still use it with the ATS present.