[RE-wrenches] Inverter Failure Due to Generator Backfeed (?)

Jason Szumlanski jason at floridasolardesigngroup.com
Fri Jan 29 15:05:52 PST 2016


I'm looking at two Eaton PV250 inverters that failed simultaneously as far
as we know (not my install). Everything checked out normal, but no display
and no power output. I suspect both boards are bad. Upon digging into the
scenario I discovered that the owner had a whole-house generator transfer
switch installed a while back, after the PV was installed. The PV is a load
side interconnection, so calamity should have been expected.

What are the odds that the generator caused the inverter boards to fail? I
was always under the impression that it was more likely for a generator
component to be damaged than an inverter component in this scenario. It
could be coincidence and the inverters may have just failed around the same.

Note:  ~10kW PV, 25kW Generator

Side note: The PV was interconnected at a 50A breaker on a 200A bus bar in
the main distribution panel and somehow passed inspection by an AHJ that
shall not be named... Over 120%, and also not the correct OCPD rating
anyway for these two inverters. Passed plan review and inspection...
Contractor out of business... surprise!


Jason Szumlanski
Florida Solar Design Group
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