breakers only trip once

[jbwhite]

the rumor mill where i work has a statment, supposed to be from an electric engineer, that circuit breakers are only guarnteed to trip once.

does anyone have a link to some standard that would either prove or disprove this statement.

i cant seem to get the name of the original engineer or i would go ask him myself.

 

[kentirwin]

Re: breakers only trip once

I believe that manufacturers test/certify breakers according to their full fault current rating. I think the "guarantee" is the breaker will then trip under these max circumstances once more while in field service. Seldom does a breaker operate under such extreme circustances. I'm sure somebody will add something to this. It's been some time since I heard the explanation.

 

[charlie b]

Re: breakers only trip once

I have heard that rumor also. I think it was intended to apply to molded case circuit breakers, such as those used in residential panels. The suggestion (I'll not call it a recommendation) that I was given is that if a breaker in my home panel trips on overload, it is a good idea to replace it.

I have no facts to confirm or refute this rumor. But let me ask: When you buy breakers to install in residential projects, is there any instructions or written guarantee that comes in the box? Is it possible that you could find your answer there?

 

[pierre]

Re: breakers only trip once

I just emailed most of the major brand circuit breaker manufacturers, lets see what they have to say.

 

[zog]

Re: breakers only trip once

I have read that alot of the cheapo GFCI's are only gaurnteed to work once, maybe that is what he is refering to

 

[realolman]

Re: breakers only trip once

Originally posted by charlie b:
The suggestion (I'll not call it a recommendation) that I was given is that if a breaker in my home panel trips on overload, it is a good idea to replace it.

That sounds like a fuse

 

[jimwalker]

Re: breakers only trip once

If they are no better than a 1 time deal then we are better of with screw in fuses.Are they to call an electrician every time they trip a breaker :roll:

 

[pierre]

Re: breakers only trip once

SqD already replied to my email effort earlier today. The reply says that the MCCB are only waranteed for 18 months from the date of purchase.

That is pretty clever on their part, I never new that.

 

[ryan_618]

Re: breakers only trip once

In order for a breaker to get an AIC rating, it must withstand the test current for which it is being rated for, trip, then reset. They don't test them again after that. So...will a breaker that has experienced a fault at its AIC rating offer the same AIC rating twice? I don't know, but Bussmann fuse sure talks a lot about it!

 

[bphgravity]

Re: breakers only trip once

What bothers me is that the manufacturer's don't indicate anything to like at all in their literature or instructions. Most breakers and breaker enclosures come with breaker resetting instructions. Sometimes they tell you to consult an electrcician, sometimes they don't. But never have I seen one state the breaker may no longer fuction properly and thus needs replacing, it only tells you how to get the breaker reset.

 

[charlie tuna]

Re: breakers only trip once

i was once told by an engineer that branch circuit breakers are actually designed to trip at a lesser amperage each time they trip. and it has been my expieriance that troubled circuits, where the breaker trips on a regular basis, does trip at a lower setpoint after many resets.

and the screw in fuse is much more dependable than a circuit breaker.................

 

[pierre]

Re: breakers only trip once

Eaton returned my email early this morning. Their response is the breaker is under warranty, and does not loose it's warranty if it trips due to faults or overcurrent.

GE also responded this morning. There response was a list of phone numbers to different tech departments (10)- of which I am not sure which to call. At least 1-800 numbers though.


So, 2 (Eaton, SqD) say that the breakers are under warranty, then the rest is history. GE I still have to call.

So I wonder... do we have to change breakers after 18 months if they were to trip? Or do we have to change them after 18 months regardless?

 

[ed downey]

Re: breakers only trip once

Pierre,

I think your missing the point on the 18 month warranty. Just like waranties on just about every other piece of equipment there is a limit to how long the manufacturer will be responsible. It is not a lifetime guarantee. If their product worked correctly for 18 months it should continue to work for a longer period but they are not going to guarantee that.

I know when we construct a new building the warranties from the manufacturer are usually 18 months from shipment or 12 months from start-up which ever is shorter. Although as a GC we have to warrant the project for 12 months from substantial completion. So to get around the fact that we will use the equipment during construction for temporary power we write in the scope of work that it is the electrical contractors responsibility to provide the additional warranty (either by paying the manufacturer or assuming the risk themselves).
-Ed

 

[charlie b]

Re: breakers only trip once

The NEC requires that the stuff we install must be listed. It does not require that the stuff be guaranteed. So no, there would be no requirement to replace the breakers every 18 months.

 

[bphgravity]

Re: breakers only trip once

I guess in reality, there is nothing that can be guaranteed to work a second time or continuously. We've talked about this before with gfci devices. The test button only tells you it work THAT time and does not indicate it will again. And just because the brakes on your car worked at the last traffic stop, doesn't mean they will at the next.

 

[ryan_618]

Re: breakers only trip once

Originally posted by charlie b:
The NEC requires that the stuff we install must be listed.

I know of no code requirement that a circuit breaker be listed.

 

[rbalex]

Re: breakers only trip once

I have discussed this issue in two other threads with references to both IEEE 1015 (Blue Book on Molded Case Circuit Breakers) and NEMA AB-4 (Molded Case Circuit Breaker Inspection and Maintenance Guide):

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=11;t=004607#000011

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=11;t=003687#000003

What it boils down to is that, after clearing a fault (short-circuit or ground-fault), the future performance of a molded case circuit breaker is indeterminate. Clearing a simple overload is different the physical forces are much less and the thermal effects dissipate quickly.

 

[charlie b]

Re: breakers only trip once

Originally posted by ryan_618:

Originally posted by charlie b:
The NEC requires that the stuff we install must be listed.

I know of no code requirement that a circuit breaker be listed.

I was making a point about guarantees, not about breakers. That is why I said "stuff." I haven't seen a list of what must be listed, and what need not be listed. Where in the NEC do I find that list?

 

[ryan_618]

Re: breakers only trip once

Sorry Charlie, I thought you meant everything whenyou said "stuff". There is no list (that I am aware of), but you can refer to Annex A and get a pretty good idea.

 

[templdl]

Re: breakers only trip once

Here's a C-H application data document which outlines the testing requirements for molded case circuit breakers, UL489. Look at page 5. You should find that the testing is quite extensive to say the least.
An overview of UL489 breaker tests.
Oh, yes, and how do they test fuses to assure that they will work?