Colleagues:
Not too long ago we finished a large off-grid residential power system installation. It has a three-stack Radian 8048A with three FM80s and about 3,000 AH of battery. The home has all the bells and whistles including VFD drive pool pumps and home automation. We have been experiencing some GFI tripping on various AC branch circuits. I checked the bonding scenario and it appears to be correct: One bond only at the AC Combiner output of the inverters. We have checked N-G voltages and they seem minimal. We did find some high THD when the generator is charging the batteries, as high as 19%. I am not sure if this is voltage or current waveform distortion but I ordered a Fluke power quality meter and will be testing again as soon as it arrives. An Outback engineer told me distortion of a generator AC waveform under charging loads is normal. Unlike the recent case reviewed on this forum--where a specific appliance seemed to be causing problems in the PV GFI circuit, I have no indication that one appliance is the culprit and the problem is on the AC side. As an aside, I have always been interested in the design of PV GFI technology. It seems counterintuitive to me to deliberately un-bond any ground-referenced system and run that bond through a breaker pole. Nonetheless, the PV GFI circuit has not opened in this scenario. This does not mean there is no ground fault current, it means there is not a ground fault current in excess of 1 amps. I have reviewed all of the recent and historic posts about GFI tripping and I don’t see anything that might help. I suspect we have plumbed the depths of Wrenches current knowledge on this subject, but I am laying out the scenario in case any part of this description elicits a recollection. When we get this figured out, I will report back. Sincerely, William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985
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