It is my understanding that for an ATS per its UL listing an upstream OCPD is required in order to clear faults within the ATS specific withstand rating. I cam across a situation where an ATS is fed on the normal side directly from the secondary of a transformer with no OCPD between the transformer secondary and ATS. The emergency side of the ATS has an OCPD located upstream at the generator however there is no OCPD located on the normal side.
Is it correct that an OCPD is required to be located upstream of the ATS on the normal side according to its UL listing?
Is it correct that an OCPD is required to be located upstream of the ATS on the normal side according to its UL listing?