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houser 12-01-2006 12:39 PM

breaker life expectancy??
 
In another forum, someone noted that the tensoin spring in most breakers will start to give at around 12 cycles (trips). I'd never really thought about this before, but does this square with the good folks here in the e- forum? It sure seems low to me. I've never had one trip 12x before, but I have cycled breakers numerous times while doing odds and ends work on circuits over the years, and never given one thought to maybe playing out the breaker. Do I need to rethink this?:eek:

thanks!
houser

jbfan 12-01-2006 02:06 PM

I have never seen anything in the instructions that say a breaker will last X times of being turned on and off.
I think the other fourm is blowing smoke.

mdshunk 12-01-2006 05:10 PM

Even if the springs in the breaker did get weak after 12 trip cycles, that would present no hazard. The breaker would trip prematurely or nuisance trip. Don't sweat it. Large, commercial breakers have a special little button you're supposed to press on a scheduled interval to exercise the trip mechanism. If this was a real concern, it would be in published data from the manufacturers or in the UL book. It is in neither place. Sleep well.

LanterDan 12-02-2006 12:05 AM

Two other questions if I may.

How does this affect the use of breaker of as switches? In my area this is commonly done in, for example, machine shops during off hours. I was told once that this was bad practice, but as I said it is common. I also have numerous peices of electrical equipment (mainly DC power supplies) for which use a breaker as the on/off switch, so presumably the manufactor wouldn't do this if there where a problem, but then they aren't using "normal" breakers, so maybe they are sepcially desgined for this.

I though large commercial breakers were a PITA to reset. I basically thought one had to have a special team come out and perform various equipment tests. We where once contemplating having a breaker (which was in readily accessible location) also serve as an emergency power switch, and were told that even in an emergency we weren't ever supposed to actuate them. (I was also under the impression that some of the really big breakers were ordinance actuated.)

mdshunk 12-02-2006 09:39 AM

Quote:

Originally Posted by LanterDan (Post 25570)
How does this affect the use of breaker of as switches?

Breakers used as switches must be marked as "switch duty". It will have a the marking "SWD" on the breaker. Most branch circuit breakers nowadays are so marked.

[quote=LanterDan;25570] I though large commercial breakers were a PITA to reset. I basically thought one had to have a special team come out and perform various equipment tests. [/quote]
The reason for the "team" is to determine if a fault still exists before you reset the breaker. If you reset a very large breaker that tripped due to a bonafide fault, you could cause all hell to break loose. I have never heard of an ordinance actuated breaker, but they may exist someplace. I suspect the reason that this impression might exist is because some breakers say "ARMED" in a little window when the trip mechanism is fully cocked or fully wound. There are larger breakers that you need to pump a handle to cock the trip spring, and there are larger breakers that use a small motor to wind the trip spring.

There is required testing at certain intervals on all very large commercial breakers. These are breakers that cost in the 20,000 and up range when they are new. Insurance companies generally want them tested every few years. This is done on site, by companies that specialize in such testing.


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