SolarEdge DC Isolation Fault when it rains?

[Oliver84]

I've been having an issue with my solar panels for 5 months now and nobody seems to be able to figure out what the problem is. My system has 2 inverters with 20 panels on each inverter. Given the title, one would probably assume the problem must be a bad connection, right? Well, we've tried so many things and still have yet to find out what the problem is. We've replaced both inverters, so that's been ruled out. We used a megger tester to try and find the isolation but the readings weren't very helpful. We've tried splitting the strings, unmounting and mounting everything again, and replaced some connectors that were thought to have been "faulty". After all this, we still had an issue where 1 inverter was totally fine and the other was just seeing 8 panels out of the 20. The technician when and checked all the wiring again and said that everything checked out just fine. But the system still wasn't reading all 20 panels. Then we had a big rain storm come in and now both of the inverters have shut down because of a DC Isolation fault.

I'm not sure what else to try besides replacing each and every connector, which I'd like to try to avoid if possible. I can't see how each connector would be bad, I'm hoping there's a way to find the bad connectors and just replace those. But the problem seems to be more apparent when it rains, so I'm not sure how we can really test for this faulty connector without the rain. Do any of you here have suggestions? I've searched and found similar issues, but all the solutions we've tried haven't worked thus far.

[PVAndy]

Are any of the connectors lying on the roof? We've seen this issue when they are. Also have you asked SolarEdge support to diagnose? They can be helpful

[Oliver84]

No, they all seem to be connected. We've checked them several times and the odd thing is that one of the inverters were just fine before. But now both are stuck in a "reboot" loop showing an isolation fault in each.

I've contacted SolarEdge and they say they can't do anything from their end, that the installer needs to call them on site. As far as I know, he's been doing everything they ask him (he's shown me chat conversations with them), and neither side seems to be able to figure out what's going on. It's the craziest thing. The installer tells me that in the 7+ years he's been doing this, he's never had a case like this that they haven't been able to resolve. But it's been 5 months now and I feel like we're still on square one.

I'm not sure what else it could be. DC Isolation fault when it rains. Doesn't sound like that would be super difficult to figure out but it's got us really stumped.

[J.P.M.]

Another happy SolarEdge user.

[oregon_phil]

Oliver84 , a quick search revealed a Solar Edge Isolation fault troubleshooting guide. Did your technician follow the SE guidelines?

Pretty basic troubleshooting. Start at the string level then work your way down to component level. Don't jump to any conclusions regarding the potential cause of the problem because you might never get to root cause.

You have already spent 5 months trying to solve the problem. Worse case: You follow the SE document and finally have to uninstall everything to test each component individually.

If the SE document is any good, you might not have to uninstall everything.

I am a fan of Kepner Tregoe to help solve complex problems (this is a complex problem); especially the problem analysis section. Specify the problem, Identify differences and changes, formulate potential causes, then prove root cause. This probably doesn't appear to be very helpful to you right now. The data that you gave in post #1 is very general and your installer has already tried the easy stuff.

I am not an installer and do not own SE equipment, but have been a design and process engineer all of my working life. Troubleshooting complex problems is hard work.

If I had your system, I would get the schematic from your installer and write everything down on that schematic that you know about your system. For every solar panel, optimizer & inverter record model numbers, serial numbers, date codes. Identify optimizers on the schematic that can and can't be identified. What is the same for each system, what is different.

[PVAndy]

Another happy SolarEdge user.

We have several thousand SolarEdge systems installed and while we do have problems, no where near what you would expect from reading this forum. Many issues traced to installation issues

Andy