400A ATS and 600A bkr

hhsting

Senior Member
I have 400A ATS life and safety branch protected by upstream generator breaker of 600A and while normal side breaker size is 400A. Is that correct or should generator breaker be 400A? What code section regarding this?
 
Thanks, yeah I should have clarified I meant per NEC. Yes manufacturer may have such a requirement.

Another important thing for OP to consider is frequently with transfer switches, the SCCR is effected by what OCPD is ahead of it. I have had to go up to a 400A ATS fed by a 200A frame breaker to get the SCCR I need. If I was a plan reviewer, I would ask to see the charts and sccr rating.
 

hhsting

Senior Member
Thanks, yeah I should have clarified I meant per NEC. Yes manufacturer may have such a requirement.

Another important thing for OP to consider is frequently with transfer switches, the SCCR is effected by what OCPD is ahead of it. I have had to go up to a 400A ATS fed by a 200A frame breaker to get the SCCR I need. If I was a plan reviewer, I would ask to see the charts and sccr rating.

Ok thanks. ATS is an electrical equipment. Wonder why there is no section in NEC 2017 to require its protection? Whats the logic behind that?
 
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