Commercial PV Design Questions

[pvgreeze]

The SE120K-US has 144.3A maximum rated output current, which takes a minimum 180.4A OCPD, which rounds up to 200A. There is nothing "bizarre" about that; that it does not land directly on a standard OCPD size is the rule rather than the exception; most inverters don't and there is no reason why they should.

I have a hundred or more commercial PV systems under my belt in many different AHJ territories and every single one of them evaluates my PV AC combiner panels for compliance with 705.12(B)(3)(3).

Got it, thank you!

 

[mddorogi]

Conductors do not need protection from the inverters; they are sized to withstand 125% of the maximum current that the inverters are capable of sourcing. All the OCPDs on the AC side are to protect the conductors from fault current coming from the utility; that is why they are on the other end of the conductors from the inverters. My guess that the two PEs who think a main breaker is necessary on an inverter combiner panel are not very experienced in dealing with PV.

In cases where the combiner panel is not co-located with the metering and disconnect equipment, would there be a requirement for a main breaker in the combiner? For example, if the combiner panel is on an outside wall, and the rest of the equipment inside an electrical room. I see nothing in the code that would say so.

 

[jaggedben]

In cases where the combiner panel is not co-located with the metering and disconnect equipment, would there be a requirement for a main breaker in the combiner? For example, if the combiner panel is on an outside wall, and the rest of the equipment inside an electrical room. I see nothing in the code that would say so.

Short answer: no. It's no different from any other panel. As long as it has overcurrent protection somewhere else, it doesn't need it at the panel. There might be an essentially unrelated reason to do it, like you need a disconnect because it's at a separate structure, etc., etc. But otherwise no.

 

[Ken70]

Is the switchgear section which has the PV fused disconnect switch rated for 3000A (or less)?

often the distribution section(s) bus bar ratings are less than the MB section, this changes the calculations and location on a load side POI