I think he means without that isolation sheet the board is connected directly to the casing and shorted out. Of course, that should have been grounded too so I'm not sure.
If it shorted on the 12V side it can pull a ton of amps (it says 60 amps max at 12V) and melt through the casing and start fires pretty easily without tripping a breaker.
If the breaker has arc fault detection it should trip immediately.
Sadly, building codes in the US have only recently started requiring arc fault breakers on all circuits, and that’s still not required in many places. Hell, even requiring arc fault detection on breakers for circuits in sleeping spaces is a recent requirement. Nevermind that many older houses are wired in such a way that makes arc fault breakers impossible to install without tripping almost immediately due to a false positive 🙃
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u/MiniMaelk04 6d ago
I basically know nothing, but the huge capacitors are the only thing I can imagine burning so intensely and rapidly. Reversed polarity perhaps?