On Monday, July 10, 2017 at 7:29:52 AM UTC-4, Terry Coombs wrote:
On 7/9/2017 8:28 PM, Lenny Jacobs wrote:
When a breaker is tripped, it's always the main breaker, not the
individual breaker. Shouldn't the individual breaker be tripped first?

This is troublesome because I then have to turn off all individual
breakers with the main breaker on and flip each breaker to see which
one causes the trouble.

That ain't supposed to happen . When an individual circuit overloads
that breaker and only that breaker is supposed to trip . Either you have
a defective main or the wrong amp rating . Or maybe you've got way too
big breakers on the individual circuits . Most mains are 100 or 200 amps
, 30 or 40 amp breakers for stoves/water heaters/dryers , 20 amp for
most outlet circuits and 15's for lighting .

--

Snag

See Clare's post. If you have a panel full of breakers and most are loaded
near the max, you can be at the main breaker limit. Turn on one more load,
add 5A on a circuit that is already pulling 9A, or even on a circuit
that wasn't drawing anything, and it will trip the main. Someone else
pointed out that if the load is unbalanced, you could also exceed the
max on one leg in a similar way. It;s unusual, but so is his problem.

Another question is if the problem is being caused by the addition of
a normal additional load or a dead short. A dead short can exceed both
the main breaker and the individual circuit breaker at the same time.
Normally just the individual one opens, but it's possible that he has
a fast response time main and a slower response time individual breaker.
I tend to doubt that though, those kind of shorts you'd think you'd
know and they would not be intermittently happening again.
breaker, not the individual circuit breaker.