On 2017/02/03 2:41 PM, Jon Elson wrote:
Had two circuit breakers do something odd at home. One tripped, and I
assumed somebody had a space heater and a hair dryer on at the same time or
something. Then, a breaker for my computer room tripped when I turned on a
laser printer. No unusual loads that I haven't done a hundred times before.
I unplugged the laser printer, thinking it might have given up the ghost.
When I reset the breaker, it was noticeably warm, which seemed odd, as it
was not feeding a heavy load. The laser printer and everything else was
just fine.
It took a couple hours for the breaker to cool. I can't remember for sure
if the breaker that tripped earlier had also been warm, but it might have.

So, anyway, it seems these breakers developed poor contact after just
staying turned on for several years, and needed the contacts cycled to wipe
them clean. I have some other breakers in the shop that are used as
shutoffs for various machines, and they never do this, I guess because the
contacts are exercised routinely.

Jon


It is not the breaker per se that was overheating here, it was the
breakers contacts to the power bus! I suggest you take that breaker out
(safely!!) and check for signs of overheated junction pins on both the
breaker wipers and the bus tab.

Had this happen to a friend and it could have been nasty if they hadn't
noticed it.

John

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