What made this installation (again, by others) a bit more complicated was that all branch circuit line conductors were black. I make it a point on my installations to require black for L1 and red for L2 up to #6 wire size. It's not a failsafe by any means but does reduce risk.
On Thu, Jan 23, 2020 at 2:41 PM August Goers <[email protected]> wrote: > Jason - > > Thanks for sharing - this is a good lesson for all Wrenches. Years ago we > had a dual string inverter installation where the DC positives and > negatives were mixed between the two interters. String 1 positive went to > inverter 1, string 1 negative went to inverter 2 and vice versa. The > inverters tested out and ran for about two weeks and then one of them > literally caught on fire. Since then, we implemented a policy of checking > wiring coming from the roof down individually. In the case of microinverter > branch circuits, this means checking each branch circuit voltage on the > roof with the other breakers off one branch at a time. > > Not to get too far off on a tangent, but as we're installing more and more > energy storage with lots of onsite wiring work, it is clear that fully > testing wiring is of utmost importance. We have a procedure for checking > voltage at each piece of equipment (such as a backup loads panel, etc) > prior to turning on branch breakers. We've run into a couple of > scenarios where hots and neutrals were mixed up causing 240 v to go to a > 120 v circuit. Not good. > > August > > On Wed, Jan 22, 2020 at 2:58 PM Jason Szumlanski < > [email protected]> wrote: > >> I discovered the issue I believe, so I thought I'd update all of you who >> gave me ideas on what to look for (thank you). >> >> And this is something that I stress the importance of all the time... >> >> The branch circuit pairs were not properly paired up! All of the L1 >> conductors went to L1 on the bus and all of the L2 to L2. However, for >> example, circuit 1 L1 and circuit 2 L2 were on a single 2-pole breaker. And >> circuit 2 L1 and circuit 1 L2 were on another breaker. Everything worked >> because it was electrically connected to the right bus bar. However, when >> there was a previous fault one of the breakers probably didn't trip when it >> should have as a result of the improper pairings. It was reset a few times >> and just kept heating up and heating up. >> >> This isn't conclusive, but it sure makes sense. It wasn't fun tracking >> this down with 5 strings and 5 junction boxes on the roof, but once we >> started continuity testing and finding strange results, it became clear. >> >> Jason Szumlanski >> >> >> >> On Tue, Jan 21, 2020 at 12:10 PM Jason Szumlanski < >> [email protected]> wrote: >> >>> (System installed by another contractor...) >>> >>> I have been tasked with assisting in the investigation of damage in a >>> subpanel used to combine inverter output circuits (5 strings of >>> microinverters). There appears to be no damage to conductors or other >>> system components. It looks like the damage started at the stabs of the bus >>> bar where the breakers connect. Picture attached. Here are a few clues: >>> >>> - Monitoring indicates that damage occurred overnight a few weeks >>> ago. That night we had rain as a winter front came through Florida, >>> possibly lightning. The prior day everything was fine. >>> - The next morning, only 2 of 5 strings started producing power, but >>> 4 of 5 strings were reporting data to the Envoy. The two strings that >>> were >>> reporting but not producing power reported 0Vac and Voc on the DC side of >>> the microinverters. >>> - A couple of weeks later, 1 of the 2 strings that was producing >>> power quit doing so, but continued reporting data. >>> - Customer discovered damage yesterday. >>> - About a week before the initial damage apparently manifested >>> itself, another contractor installed a whole house generator transfer >>> switch on the line side of the PV interconnection. The generator has >>> never >>> been run (there is not even a LP fuel source on site yet). I pointed out >>> that the solar interconnection, which was previously on the supply side, >>> would need to be moved to the supply side of the generator transfer >>> switch's main breaker before operation. During the transfer switch >>> installation, the contractor also switched line 1 and line 2, but that >>> shouldn't really matter, except for Enphase consumption monitoring, which >>> was messed up by the swapping of the lines. >>> >>> So I'm looking for ideas. I'm wondering if the OCPD would be a likely >>> place for lightning damage to manifest itself. I can't visually detect any >>> other damage anywhere else. I can't imagine that the transfer switch >>> installation would have anything to do with it, but the timing is >>> interesting. Other than replacing the subpanel and OCPD and firing it back >>> up (no pun intended), I'm not sure how to approach further investigation. >>> >>> Jason Szumlanski >>> Florida Solar Design Group >>> >>> >>> _______________________________________________ >> 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 >> <https://mailtrack.io/trace/link/0630738790020bf17b7774ad6ed4464425204c4b?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=636f6272fa7ddeb8> >> >> List-Archive: >> http://www.mail-archive.com/[email protected]/maillist.html >> <https://mailtrack.io/trace/link/723f771ba6190c7b8fc2fd06f31ea7a6b6ab41c0?url=http%3A%2F%2Fwww.mail-archive.com%2Fre-wrenches%40lists.re-wrenches.org%2Fmaillist.html&userId=1613865&signature=f6676786e8e04410> >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> <https://mailtrack.io/trace/link/d7ea9ae3eaf8765631db5d80b47f3267e01120c0?url=http%3A%2F%2Fwww.re-wrenches.org%2Fetiquette.htm&userId=1613865&signature=7b3d598ee513f514> >> >> Check out or update participant bios: >> www.members.re-wrenches.org >> <https://mailtrack.io/trace/link/01c37be05208c0de420580d892b553f82dfadc19?url=http%3A%2F%2Fwww.members.re-wrenches.org&userId=1613865&signature=01eb85f151b00d5d> >> >> _______________________________________________ > 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 > <https://mailtrack.io/trace/link/36360340e428b3c123126012a4fa231afa4d6f05?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=ed994c188e79c2d3> > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > <https://mailtrack.io/trace/link/6cd516775bc1800cf14b878dba3290cc3ab86de6?url=http%3A%2F%2Fwww.mail-archive.com%2Fre-wrenches%40lists.re-wrenches.org%2Fmaillist.html&userId=1613865&signature=1c8f4f1539e9183a> > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > <https://mailtrack.io/trace/link/9c3fae629a074d4c8ae47e0eaf0c5201471c0b1d?url=http%3A%2F%2Fwww.re-wrenches.org%2Fetiquette.htm&userId=1613865&signature=6fda5140d3ecc484> > > Check out or update participant bios: > www.members.re-wrenches.org > <https://mailtrack.io/trace/link/ad276d8b16d068c12a6ea6c0cd4c11cbd1f413a5?url=http%3A%2F%2Fwww.members.re-wrenches.org&userId=1613865&signature=92016f985d4b96d5> > >
_______________________________________________ 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
