Chris Lewis wrote:
According to Ajax :

When one of our neighbors came back from vacation they found that the
20 amp single pole breaker for their hot tub and the 20 amp single
pole breaker for their refrigerator in their detached garage had
tripped. Neither GFCI type outlet served by these breakers had
tripped.


then stuff about a subpanel breaker going.


Sounds to me that they have to go over the innards of the main,
and the feed line to the subpanel inch by inch. Wearing
eye protection and gloves, wiggle the cable on every staple and
box clamp. Check for wire exposure on the inside of every box,
gaps in tape covering of splice connectors etc.

It could be a piece of defective cable, or an over tightened
box clamp that only causes a short when the cable moves (thru
temperature changes, wind shake or whatever).

I have encountered defective cable where it's not possible to see the
defect, even after it's blown the breaker multiple times. In
my case, it was a solid short. In this case it sounds like an
externally-induced intermittent.

An intermittent short of this nature won't be detectable with any
kind of metering until its fried the insulation enough to provide
a carbonized conduction path. You don't want to let it go
that far...

Either that, or they have gremlins.

Run the thermal detector over the inside of the main panel
and subpanel too.

That thought just occured to me as well. Breakers are not electronic
but thermal in nature. If that room of the house became very hot for
whatever reason, you could get a lot of trips from odd circuits.

Also check for water or other conductive fluid leaks in the area of the
panel.

--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16