pic: 3692's PDP after catching on fire at Queen City

[DonRotolo]

Originally Posted by kpie3692

It was for sure a massive short but the inline breaker and the main breaker never tripped throughout the fire.

Just a comment on circuit protectuion devices (such as fuses and circuit breakers): They are designed to limit the current or open the circuit after a certain current and time has been reached, and they do so quite reliably. However, there are circumstances where they cannot help: An Arc.

An arc is electrical current flowing across a 'space', a gap in the conductor, creating a (relatively) low-resistance plasma which conducts the current. An arc can have a resistance on the order of an ohm, which for 12 volts means maybe a dozen or two Amps - not enough to trip a 40A breaker, but plenty of energy to get real hot, real fast.

I work in the automotive industry, and while this is not my area of expertise, we know that a 30A circuit can form an arc that starts a fire but does not blow the 30A fuse. The arc sustains itself for a 'long' time (more than several seconds, sometimes several minutes).

You likely know what a GFCI (Ground-Fault Circuit Interrupter) is, but look up the term "Arc-Fault Interrupter". The National Electric Code began asking for (or maybe requiring, not certain) AFCIs in all new wiring circuits serving bedrooms back around 2002. They did this because arcs start fires and conventional circuit breakers cannot do anything about it because the arc does not draw enough current to trip one.

All that being said: An arc may have formed (won't speculate why or how, or really even if) that drew less than the circuit breaker's rating, and the resulting plasma arc (several thousand degrees) appears to have started a fire.