PV AC conductor sizing

[Mikemezz]

What should the conductor size on a PV system with five 10k inverters each 27.79amps x 1.25 = 34.73 amp be between 175amp AC combiner panel and the 175amp linetap disconnect.
We are using NEC 2008 does the wire size need to be the sumof 2 x 175amps are we required to use cable rated at 350amp.

 

[Marvin_Hamon]

You did not give quite enough information so let's make some assumptions:

3 phase system with 3 phase inverters.

Each phase has 5 35A circuit breakers in the AC combiner.

The 175A AC disconnect has 175A fuses.

The conductor has the equivalent of a 175A OCPD on each end so it would be sized to carry 2*175/1.2 = 292A to be code compliant. Most people would size it to be protected by the 175A OCPD and either hope the AHJ did not catch it or, like me, submit an Alternative Methods and Material request to the AHJ to reduce the size of the conductor to 175A based on it being dedicated to the PV system.

Your AC combiner should also be sized to carry at least 292A to be code compliant also, but then again I bet most would go with the 175A panel.

 

[Mikemezz]

PV AC cunducter sizing

PV AC cunducter sizing

The info is very helpful thank you are correct this a a 3 phase 208 with 3phase inverters i did the same math except dividing by the 175 x2 = 350/1.2 why do you devide by 120%

 

[Marvin_Hamon]

NEC 705.12(D)(2)