[RE-wrenches] Enphase String Breaker Heating Up

Jason Szumlanski jason at floridasolardesigngroup.com
Thu Aug 4 11:11:39 PDT 2022

I have a commercial 208 volt job where four of 11 fully populated strings
of IQ7A had breakers that were tripped as reported by the client. They were
able to reset two of them. They also reported that the two they were not
able to reset we're very hot. The other two were warm.  By the time I got
to the site, all four breakers had permanently failed.

Once I got replacements, I was able to install them and they turned on
without any faults. I gave it about 15 minutes and then put my infrared
camera on it. To my surprise, the breaker immediately above two of the
failed breakers and across from the other two failed breakers was clearly
hot. I'm thinking this might have been the bad breaker all along causing
the heat issue on the bus bar which made adjacent breakers fail. But this
hot breaker did not fail.

Does this seem like a plausible scenario, and if so, any ideas on what
might have caused it? All of the breaker bolts were tight, but a couple
were not torqued to spec. I just find it strange that one breaker that
didn't fail would cause other adjacent breakers to heat up enough to fail.

Flir image attached. This was after I replaced the four failed breakers.

Jason Szumlanski
Florida Solar Design Group
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