On Friday, December 25, 2015 at 10:31:41 PM UTC-5, IGot2P wrote:
Approximately 8 years ago I built (with the help of a contractor) a
1,200 sq. ft. shop detached from our home (nice shop with central heat
and air, half bath, hot water, etc.).

Our home has a 200 amp box so I simply put in a 100 amp breaker and run
it to a sub panel in the new shop which has a 100 amp breaker box.
Everything in both the shop and house has worked fine since the
beginning and still does but I did find something somewhat unique.

I have one item in the shop that draws 23+ amps on a 115 volt circuit
and to my surprise had never popped a 20 amp circuit breaker. All
outlets and lights are wired with #12 wire so I know that 23+ amps is a
bit too much but so be it. Well, I moved the item a small amount and
happened to plug it into a different outlet which happened to be on a
different breaker and it popped the breaker after running for about 20
minutes. Tried it again and the same thing happened. Out of curiosity I
checked the voltage and that particular circuit (the one that the
breaker pops on) has 125 volts and all of the others run in the 115/117
range.

Anyone have a clue of how this could happen when they are all coming out
of the same box and are approximately the same distance from the box?

BTW - if you intended reply contains the word "code" or "insurance"
please don't post as it has nothing to do with my question.

te breaker that trips may have tripped a lot in its past, and be worn. for lack of a better term.

i would first try replacing the breaker that trips