"TimR" wrote in message
...
I tried to google to find out how long a circuit breaker will last.

It turns out quite a while, on mechanical operation or overload.

One Square D breaker I found data for was rated at 12,500 cycles mechanical
operation (meaning you turned it off by hand) and 2,800 electrical
operation (meaning it overloaded but did NOT fault). I would think
mechanical operation would depend on how much current was being drawn at
the time, and I always try to turn off loads before flipping a breaker
just in case. We had a nasty explosion in the plant once when somebody
flipped a disconnect under load.

I could not find the fault rating for that breaker but several other
searches said a breaker is guaranteed to interrupt the full fault current
(meaning a short) ONCE, and should be replaced after twice. So Stormin and
his .buddy just reduced the life of that breaker by 50%.

AND: violated OSHA in the process. OSHA says it is forbidden to
re-energize a tripped breaker without inspection and testing, UNLESS it is
known that the trip was caused by a simple overload and not a fault
current. The arcing of a fault current can damage the contacts that have
to open to interrupt the .current. .OSHA .applies to a workplace, I'm not
sure if that includes a church or not. Anyway, that breaker .did not see
a routine overload, but full bolted fault current.

There are several kinds of breakers. Some are made to use as switches such
as cutting lights off every night and some are not to be used as switches.

I could send some pix of an explosion where I worked. This was in a 480
volt 3 phase motor control center that was fed with another breaker of about
300 amps. The MCC has about 10 rows and 5 motor starters and breakers, each
one about a foot square. An electrician turned on a 15 amp
breaker/disconnect and something arcked and took out most of the MCC.



---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com