earshavewalls
Bronze Member
I have an ongoing discussion with a PV designer concerning bus ratings on the AC side of the inverters. (2010 California Elect. Code, based on 2008 NEC).
Setting aside 690.54(A)&(B), 705.12(D)(2) (Interconnected Electric Power Production Sources) contains similar verbiage concerning not exceeding 120% of the rating of the busbar based on the ratings of the overcurrent devices in circuits supplying power to the busbar. The argument from the designer is that you can exceed the rating of the busbar as long as no branch circuits (loads) are expressed in the panel. In other words, they feel that they may use load centers as AC combiners for the output of the inverter(s) and do not need to take into account the power from the utility at the busbar(s).
I have trouble going along with this, but at the same time see what they are trying to say.....they are not adding loads to these panels, they are only passing power through them, for the most part in one direction (except for the inverter power from the utility), and they suggested signage on each of the AC load centers stating that no loads are to be installed on these panels (that option is not in the code, either).
I am leaning toward interpreting that they must consider the feeds from BOTH directions (Utility and the PV output) for each AC busbar that are connected to each power supply, even if they add signage dissallowing any loads on these panels.
Any input out there? Give me something that helps their case, if you can......otherwise, I've been right all this time.....and we can't have that!
Setting aside 690.54(A)&(B), 705.12(D)(2) (Interconnected Electric Power Production Sources) contains similar verbiage concerning not exceeding 120% of the rating of the busbar based on the ratings of the overcurrent devices in circuits supplying power to the busbar. The argument from the designer is that you can exceed the rating of the busbar as long as no branch circuits (loads) are expressed in the panel. In other words, they feel that they may use load centers as AC combiners for the output of the inverter(s) and do not need to take into account the power from the utility at the busbar(s).
I have trouble going along with this, but at the same time see what they are trying to say.....they are not adding loads to these panels, they are only passing power through them, for the most part in one direction (except for the inverter power from the utility), and they suggested signage on each of the AC load centers stating that no loads are to be installed on these panels (that option is not in the code, either).
I am leaning toward interpreting that they must consider the feeds from BOTH directions (Utility and the PV output) for each AC busbar that are connected to each power supply, even if they add signage dissallowing any loads on these panels.
Any input out there? Give me something that helps their case, if you can......otherwise, I've been right all this time.....and we can't have that!
