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--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Colleagues:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I have reviewed all of the recent and historic posts about GFI tripping and I don\u2019t 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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Sincerely,</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">William Miller</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">Miller Solar</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">17395 Oak Road, Atascadero, CA 93422</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">805-438-5600</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif""><a href="http://www.millersolar.com/">www.millersolar.com</a></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">CA Lic. 773985</span></p><p class="MsoNormal"> </p></div></body></html>