Reviewing a design for a solar PV system that is tying into a panel. This panel is located in a parking garage and is fed from another distribution panel in the main building which is fed from the utility.
The inverter from the PV system is a 250kW inverter and therefore requires a 400A breaker at the interface panel. The interface panel has an 800A rated bus with an 800A breaker.
Looking at this it appears to be a violation of 705.12(D)(2) which says that the OCPD's from the PV inverter and the panel utility supply feed (in this case fed from an upstream panel) cannon exceed 120% of the bus rating. 120% of the 800A bus rating is 960A which is less than the 1200A total of the two breakers. Am I right in saying that there is a problem here even though this panel isn't fed directly from the utility but is fed from the utility source via an upstream distribution panel?
The way I see it we have (2) options which would be to either 1) verify that the interface panels buss is capable of 1000A continuous rating, or 2) if possible reduce the main breaker to a 500A breaker if the bus is only rated for 800A continuous duty.
Since the inverter is rated at 250kW then it needs to have a 400A breaker at the interface per the NEC.
Do you guys agree with the two options above?
What if the main breaker is an 800A frame but is set for a 500A trip setting. I assume its the trip setting we're concerned with, not necessarily the frame size?
The inverter from the PV system is a 250kW inverter and therefore requires a 400A breaker at the interface panel. The interface panel has an 800A rated bus with an 800A breaker.
Looking at this it appears to be a violation of 705.12(D)(2) which says that the OCPD's from the PV inverter and the panel utility supply feed (in this case fed from an upstream panel) cannon exceed 120% of the bus rating. 120% of the 800A bus rating is 960A which is less than the 1200A total of the two breakers. Am I right in saying that there is a problem here even though this panel isn't fed directly from the utility but is fed from the utility source via an upstream distribution panel?
The way I see it we have (2) options which would be to either 1) verify that the interface panels buss is capable of 1000A continuous rating, or 2) if possible reduce the main breaker to a 500A breaker if the bus is only rated for 800A continuous duty.
Since the inverter is rated at 250kW then it needs to have a 400A breaker at the interface per the NEC.
Do you guys agree with the two options above?
What if the main breaker is an 800A frame but is set for a 500A trip setting. I assume its the trip setting we're concerned with, not necessarily the frame size?