Thanks Nicholas for passing on this information. We have a couple of recent sites where we upgraded old string inverters to modern models and found intermittent ground faults originating from the modules. I think the modern inverters have more sensitive ground fault sensing. One system was with ~2015 SunPower modules, which was covered under warranty by Maxeon and the other was for ~2008 Sanyo modules. The SunPower modules showed visible separation of the cells and backsheet from the front glass. We haven't yet confirmed the situation with Sanyo, but I thought I would just mention that these ground faults are hard to deal with. As you mentioned, they may be intermittent and appear more often during wet weather.
August On Tue, May 5, 2026 at 9:16 AM Nicholas Ponzio via RE-wrenches < [email protected]> wrote: > Wrenches, > > Sharing a finding from this week that I figure plenty of you are running > into and may not have connected the dots on. I know I hadn't until > yesterday. > > We pulled an old array off a roof in Vermont. Not our installation. > Modules were Schuco, vintage ~2010. Client asked about reinstalling vs. > replacing, and that question sent me down a rabbit hole. > > It turns out Schuco issued a formal product safety warning in 2022 > covering modules delivered from 2010 to 2014. The polyamide backsheet from > a specific supplier can develop chalking and cracking along the internal > cell connector. When this happens, the panel frame can become electrically > live. Critical detail: inverter shutdown does NOT eliminate the hazard > while the panels see sunlight. The manufacturer's own remediation guidance > is to uninstall and dispose of panels. UK Government issued a formal > product safety alert (2211-0050). > > That alone was news to me. But the bigger story is that this is not a > Schuco-specific defect. The polyamide backsheet failure mode is > industry-wide for the 2010 to 2014 era. DuPont's 2019 field reliability > study estimated 12 GW of field failures from PA backsheet through-cracks. > Schuco is unusual in that they actually published a recall. Most of the > other affected manufacturers either went out of business (Solon, Scheuten, > Conergy, Suntech) or quietly handle replacements case-by-case without > public notification. Trina, Yingli, early Canadian Solar, Jinko, Renesola > all show up in field failure literature for this era. > > Why I'm posting: > > 1. We've installed a few of these brands in that window ourselves. I'm now > building an outreach list to proactively notify those clients. I'd be > surprised if I'm the only one in this group with legacy 2010 to 2014 > systems that warrant a second look. > > 2. Symptom that prompted me to dig deeper: we've had multiple clients this > winter reporting intermittent DC ground faults, mostly in cold/wet > conditions, that clear up in dry weather. Classic signature of insulation > breakdown in cracked PA backsheets. Insulation resistance drops with > moisture, recovers when dry. If you're seeing winter-correlated GFDI events > on legacy systems, this is worth checking before chalking it up to age. > > 3. Field protocol matters. Treat suspect arrays as energized regardless of > inverter state. Insulated gloves, photograph nameplates and serial numbers, > and document backsheet condition. Visual cues: chalky white residue, fine > cracks between cells, yellowing, powdery feel when wiped. > > 4. For confirmed-recall modules (Schuco MPE in the affected serial range): > do not reinstall. Manufacturer guidance is to uninstall and dispose. For > other PA-backsheet modules without a formal recall, treat the decision as > an engineering judgment call. Visual inspection (chalking, cracking, > yellowing) plus insulation resistance testing should be your minimum bar > before considering reuse. My personal bias is heavily against reinstalling > any 10+ year old PA-backsheet module given the cost of labor vs. the risk > profile, but that's a business call, not a safety mandate. > > References for anyone who wants to dig in further: > > - Schuco product warning (2022): solarpowerportal.co.uk article "Schüco > issues product warning over potential defect in solar modules" > - pv-magazine coverage of the expanded warning (Nov 2022) > - UK Gov product safety alert 2211-0050 > - DuPont 2019 Global Field Reliability Study (12 GW failure estimate) > - ScienceDirect, Eder et al, "Error analysis of aged modules with cracked > polyamide backsheets" (2019) > > I searched the list archive and didn't see this come up before. If I > missed an earlier thread, apologies for the duplication. Otherwise, I'm > curious whether others are seeing the winter ground fault pattern, and how > folks are handling client communication and remediation scoping on these > legacy systems. > > > > -- > Nicholas Ponzio > Building Energy > Williston, VT 05495 > http://www.BuildingEnergyVT.com <http://www.buildingenergyvt.com/> > > "Building Solutions for a Sustainable Future" > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/[email protected]/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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