One More Question Re House Circuit Breakers, Please ?

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Hi again,
Should have asked this as part of my previous circuit breaker question, but forgot:
Is it common or typical for an "old" house service box circuit breaker (perhaps 25 yrs old) to go bad, and trip by itself, even if there is nothing wrong with the circuit it is controlling ?
What's a "typical" life for these things ?
Thanks again, Bob
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A lot of older Murray brand will do that. The internal latch that holds the handle in the on position, just stops holding and vibrations can cause them to turn off

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yes it is............ breakers are designed to become more sensitive as they age, and its more common for a breaker to become super sensitive if its on a heavily loaded circuit.
theres no set life. but do replace the questionable breaker
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snipped-for-privacy@aol.com wrote: ...

Have you any reference from a manufacturer that is a design criterion?
Don't say it isn't so, but I've never heard or seen it mentioned in any literature which one would think would be so if were an actual design feature.
I just did a search of the entire product brochure for the Square D QO breaker series and there's no mention of "age" or "aging" or "sensitivity" throughout.
--
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hey when there trying to sell you something NEW they dont mention againg might hurt sales.......
dont have a link of one even exists, but its true of all breakers.........
a matter of liability, as it ages it has to change.
I repair office machines for a living that draw lots of current.
customer complains its tripping breaker, replace breaker trouble gone provided circuit isnt overloaded.
some machines i service have breakers built in, and they fail sensitive.
breakers trip from heat, my theory is contacts degrade a little, heat and make things more sensitive.
I used to spend a couple days a month at westinghouse beaver, breaker manufacturer. back before it was sold off, a fascinating place. nice friendly folks, who told me more than i really wanted to know about breakers. i tended to have lunch with the engineering group who were the first to talk about more sensitive with age.......... had a bunch of machines in engineering.
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snipped-for-privacy@aol.com wrote: ...

Like somebody isn't going to buy a breaker because there's a data sheet that shows it's 20-yr future sensitivity--right. :(

...
If it were a serious issue (which theoretically it would be if sensitivity were to go the other way) in the spec's I'm quite sure it would be addressed in the design phase. (And, I'm _QUITE_ sure the major manufacturers do significant aging studies.)
--
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This doesn't apply to residential, but the large industrial building where I work is having the main breakers replaced in the near future. The only reason I know about this is that obviously the power will be out for the duration of the replacement, and they have warned all of the building tenants. Apparently there is some rule about replacing main breakers in industrial and/or commercial buildings at 5 year intervals.
Ken
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Ken wrote: ...

I'd guess it's something different than just a 5-yr interval...
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I have worked at a large industrial plant for 20 years and the plant was built in 1965. As far as I know the original breakers are still in use except for a few that have failed. There are breakers from 120 volts at 15 amps to the very large 13.200 volt main breakers. Nothing gets changed unless it fails or an inferred scan indicates it may fail.
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Ralph Mowery wrote:

That's been my experience in power plants, paper mills and coal mines/prep plants as well.
There are some generating plants built in the early 50s w/ much of the original electrical controls, switchgear, etc., ...
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There's a hydroelectric powerhouse near hear that was built in 1912 and remained in use until the late 1990's. Then a new powerhouse with more efficient turbines came online, and the old powerhouse was turned into a museum. All the original switchgear still seems to be there, though it was adapted for remote monitoring and control at some point.
There are a few photos here: http://www.bchydro.com/recreation/mainland/mainland5361.html
It was built in a time when there was no power grid in the area, so it was designed to be able to start "cold", with no outside source of electricity. A bank of lead-acid batteries provided initial power, probably for instruments and DC generator field. There are a pair of DC generators, driven by tiny turbines, to provide DC armature power to the main alternators. Output voltage control seems to have been done with *large* carbon rheostats in the DC supply to each alternator.
The washrooms look like they are 1912 vintage, too...
    Dave
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On 4/8/2008 7:39 AM snipped-for-privacy@aol.com spake thus:

Ah, so it's another hallerb "theory". We can safely ignore it in that case.
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no i report what westinghouse breaker design engineers told me........
they would change with age so they were made more sensitive to trip on less current than designed........
this was better than starting a fire..
i happened to be there one day when they were testing knock off westinghouse breakers, made in mexico. looked just like the ones they produced from the outside.
when taken to 120% of rated current they exploded, a real fireball. these breakers were high voltage distribution ones
so has anyone found a breaker that wouldnt trip other than FPE stab lock??
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snipped-for-privacy@aol.com wrote: ...

...
You'll excuse me if I wait to hear from the Circle-W engineers directly what they _actually_ said and see their design criteria...
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spake thus:

no i report what westinghouse breaker design engineers told me........
they would change with age so they were made more sensitive to trip on less current than designed........
this was better than starting a fire..
i happened to be there one day when they were testing knock off westinghouse breakers, made in mexico. looked just like the ones they produced from the outside.
when taken to 120% of rated current they exploded, a real fireball. these breakers were high voltage distribution ones
so has anyone found a breaker that wouldnt trip other than FPE stab lock??
I've seen breakers of all manufacturers fail. You think Federal is the only brand that's had that problem. Try Frank Adams or Zinsco. Personally I think the only difference is that Federal sold more product
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most breakers work when needed
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From my empirical information I'd agree that breakers become more sensitive with age, at least ones that routinely control loads close to their rated limit, but I've never heard or read that it was by any kind of design. Just more unsubstantiated blather Haller pulls out of his ass
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I was / am an electrical engineer for 40 years before retiring, and have never, ever heard of such a design which is deliberately engineered to become more sensitive as it gets older. This concept for a circuit breaker is pure nonsense in my opinion.
Smarty
wrote:

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Smarty wrote:

...
That's what I think, too... :)
I can see there being an issue of a sizable _de_-sensitization w/ time if there were some physical process going on in the bimetal or similar, but I'd be quite certain if it ever was an issue it has been resolved long ere now...
--
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It's entirely possible that some aging process makes a breaker more sensitive, less sensitive, totally nonfunctional, etc. Such is the nature of any design, man made or otherwise. Things change as they age. I just wanted to make the comment that a deliberate electrical design to become more sensitive as time passes is not even slightly, remotely possible for a circuit breaker.
Now, if you wanted to argue that Detroit's engineers design shock absorbers that are deliberately designed to age in such a way as to have less shock absorption, then that is a whole different matter.........
Smarty

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