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Old 11-24-18, 07:26 PM   #3
where2
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Join Date: Apr 2013
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Thanks for the suggestions Pinball. Occasionally, it's NOT the fault of an Enphase microinverter.

In my case the microinverter was reading exactly what it was seeing. When I disconnected the MC4 terminals between the microinverter and the panel, the output was indeed well under the expected voltage. Voc on these panels is 38V at STC according to the specs on the back of the panels. So, I pulled the cover off where the bypass diodes are, and found that area was fully potted with sealant. Good design, however that makes troubleshooting more difficult.

Reluctantly, I pulled the panel out of the array to get to the back side and dig the potting material out of the junction/wiring box. Once I had most of the potting material removed, I noticed at the other end of the panel was a slight bulge in the PVA material on the back of the panel where one of the wire traces turned 90° and obviously had a solder joint in the trace material. I plugged my cheapie digital volt meter into the output leads (with the panel still facing the roof deck), and when I pressed on the bulged spot in the PVA, the voltage jumped from 17v to 24V. It almost felt like pushing a bubble membrane key switch. Hey, that's the problem!!

So, I carefully cut a postage stamp sized flap open in the PVA where the bulge was, soldered the trace back together (with my soldering gun using an extension cord to the second floor roof). I knew I had a solid connection when the voltage was at 24V watching the meter while I soldered (panel facing the roof). I sealed the open flap in the PVA with 100% silicone sealant, then covered it with tape. I replaced the potting material I had removed from the junction box on the back of the panel with 100% silicone sealant. It's not as neat as the original was, but it will work. I paid particular attention to getting the silicone into all the corners to get a good seal. When the sun comes up tomorrow we'll see if we're back in business. I suspect we will be. Time will tell if my solder connection lasts longer than the factory connection.

If this had been a typical string inverter system, that open connection would have persisted for months. Having microinverters, I was able to determine which panel had issues, and pinpoint where to start troubleshooting.

The most concerning part of the whole repair was having the panel out of the mounting system. Since this was a middle panel, the clamping system relies on the adjacent panel being in place. I was a bit concerned to leave the house to get supplies recognizing that any sudden gust of wind could upset the adjacent panels which were no longer adequately secured. In the end, I had a friend pickup the silicone and bring it to the house while I stayed on the roof minding the panels and the loose one I had upside down on the peak of the roof.
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