Hmmmm. I wonder why I'm just learning this now with thousands of micros in the wild. I did have a burned up M190 once, but that was very obvious visually and since it was not really a trunk cable situation the diagnostic steps are different.
On Tue, Jul 3, 2018 at 6:06 PM MDElectricSolar <[email protected]> wrote: > I’ve had this happen many times with Enphase micro inverters. I’ve > actually had them burn the back of a PV module. The cause was an internal > short circuit which tripped the strings circuit breaker, when I cycled the > breaker and turned it back on...... instant trip. I would put someone up on > the roof to visually and audibly confirm which micro inverter was causing > the short, it was typically very obvious to the naked eye. > > Michael D Nelson > MD Electric & Solar, Inc. > 707-684-0064 mobile > 707-884-1862 office > www.mdelectricsolar.com > www.facebook.com/mdelectricandsolar > > > On Jul 3, 2018, at 12:45 PM, Jason Szumlanski < > [email protected]> wrote: > > This is not a knock on microinverters, but information to potentially help > save the next guy a bunch of time... This is not specific to any brand, but > for purposes of explaining I will mention it was an Enphase IQ6+ system. > > One of the great advantages of microinverters, even over optimizers, in my > mind is how when a single unit fails the rest of the string just keeps on > running. I recently ran into a tripping breaker. My first diagnostic step > was to swap the string with another string's breaker to eliminate the > breaker itself as a source of the problem. That wasn't it. It just popped > the other breaker. So I probably had a dreaded wiring fault. Knowing that > pulling wires out of this particular conduit would be a nightmare, I hoped > to disconnect the string at the j-box on the roof and crossed my fingers > that the problem wasn't in the pipe. I was delighted to find out that there > was no fault in the home run wiring, so I suspected the trunk cable. To > check that I tested continuity line to line and line to ground. Nothing. > Next stop was the string terminator just to double check because I have > seen intermittent faults from a poorly installed terminator. It looked > great. I checked the waterproof caps on a couple of unused drops. Looked > good. I carefully inspected for any cuts and scuffs in the cable. No luck. > But I was convinced it was a trunk cable issue. I was just about to cut the > trunk cable in half to isolate the issue to one half of the trunk cable > when I decided to just try turning on the breaker once more. > > Pop, sizzle, boom, smoke. Found the problem. It was a microinverter with > an internal fault. Fortunately, it tripped the breaker and damage was > isolated to that unit, which was swapped out and everything was fine. > Problem solved. > > It got me thinking about my approach to diagnosing this issue. I think > next time I will start with disconnecting the string in the junction box > just like I did this time, then test and reconnect it. My next step will be > to disconnect every micro in the string from the trunk cable and test again > by turning on the breaker. Then if it's not the trunk cable or home run > wiring I can narrow down the offending microinverter by plugging in subsets > of the string. I just got lucky because it finally failed catastrophically > when I had the modules off. The owner had reset the breaker several times > before and the system ran for hours or days without issue. There must have > been an intermittent AC fault within the bad micro that finally just > manifest itself in a more demonstrative way. > > So a single point of failure can result in taking down a whole string. > That's the first time I've had that happen other than a straight-up wiring > fault. > > > Jason Szumlanski > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > >
_______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
