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Anyone ever heard of a rule about after a breaker trips once you have to replace it? This discussion came up at work.
 

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Anyone ever heard of a rule about after a breaker trips once you have to replace it? This discussion came up at work.
I've heard this discussed here once. If the breaker is subject to high fault current aka a short circuit, I believe it's considered no longer reliable and should be replaced.
 

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Um, this seems absolutely ridiculous. What the hell good do breakers do that cheaper fuses can't? I think there is a reason why there are AIC ratings on breakers.
 

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I've heard this discussed here once. If the breaker is subject to high fault current aka a short circuit, I believe it's considered no longer reliable and should be replaced.
This, though long term abuse at lower currents over time will cause the breaker to slowly degrade. And to elaborate the issue, remember these are mechanical devices the more you use em, the quicker they fail.
 

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Only under exceptional circumstances !
I think most times a breaker should be able to handle it !
Is the quality of electrical equipment really this poor ?
 

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Under a bolted fault I would. Every bolted high current fault puts the contacts. And in truth a UL listed breaker is only guaranteed at 3 fully rated faults (I think if memory is correct)
 

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Um, this seems absolutely ridiculous. What the hell good do breakers do that cheaper fuses can't? I think there is a reason why there are AIC ratings on breakers.
There is a reason for AIC ratings and that is to prevent an explosion of the breaker.
 

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Only under exceptional circumstances !
I think most times a breaker should be able to handle it !
Is the quality of electrical equipment really this poor ?
Breakers can handle the AIC and be able to reset and do it again, but UL only asks that they survive it 3 times under testing. After that its any bodies guess. Keep in mind that most commercial breakers are very close if not identical to the resi ones. All that really changes for the most part is the mounting arrangement and the arc shute/contact opening distance. Breakers where oout every time they are faulted even loaded near the trip rating. They are not fuses and require exercise and if you are talking large switchgear types one is supposed to maintain them along with testing. Breakers only really offer the convince of being reset, sometimes computer logic to and shunt trip. Other than that they are mediocre.


At the LV level especially and even the MV and HV levels in some cases fuses are superior. They coordinate better, handle faults better and are far less likely to fail if neglected.
 

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I've heard this discussed here once. If the breaker is subject to high fault current aka a short circuit, I believe it's considered no longer reliable and should be replaced.
Do you know that or are you just guessing based on opinion?

Can someone post a manufacturers white paper regarding this?
 

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I will post the pictures and NEMA standards later.

Found one of the pictures

2nd attempt to close a circuit breaker into a fault, trip and extended stay at the hospital for this electrician




When you have a CB closed into a fault there is carbon and metallic debris from the arcing contacts eventually depending on the extent of previous faults this carbon and metallic deposits can result in a fault.

AT a minimum the circuit breaker should be meggered, phase to phase and pole to pole-line to load.

I'll look for the NEMA STANDARDS
 

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lmfao a tripped breaker must be replaced!

Is this the same guy who was debating you about not having to use connectors on cables?

I'm starting to think people are just messing with you.
 

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I only throw in a main feeder breaker after everything upstream is opened.Shutdown, smallest to largest. Startup, largest to smallest is my M.O.
 

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I only throw in a main feeder breaker after everything upstream is opened.Shutdown, smallest to largest. Startup, largest to smallest is my M.O.
Well that's what you get for having common sense and a bit of electrical knowledge. :thumbsup:

Who just tries to flip a 400A breaker on after it already flipped back and told you NO! :laughing:

Probably was Brian John himself. :whistling2:
 

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NEMA says

If a circuit breaker with a
cracked case or burn
marks is found,
immediately take the circuit
breaker out of service and
replace it.

We say if there is a fault the CB should be at a minimum meggered phase to phase and pole to pole line to load. Additionally we like to ductor/micro ohm the CB and perform a visual inspection of the contacts if possible.

 

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Molded case low voltage circuit breakers are designed and tested to UL standard 489. UL uses the following test goals to determine if a breaker is considered to be safe (incompliance with their safety standard):

· The breaker must interrupt the maximum short circuit current two times.
· The breaker must protect itself and the connected conductor and the equipment it is installed in.
· After having been tested the breaker must be fully functional and pass a thermal calibration trip test at 250% of its rated ampacity; and pass a dielectric withstand test at two times its rated voltage or a minimum of 900 volts.
· The tested breaker must also operate properly and have continuity in all of its poles.

UL-489 listed circuit breakers are tested with a four-foot length of wire, as they must perform during the test as they would when installed in the real world, so wire is connected to make the test a bit more realistic. During the test the conductor’s insulation must not be damaged. The connected wires must not be pulled loose from the breaker-conductor termination lug. The breaker case must not be damaged as a result of cable whip forces (caused by the potentially huge amount of magnetic force developed under short circuit conditions). The connected wire acts to some degree as a heat sink for the breaker. That is, it helps to dissipate heat produced within the breaker. This is because the breaker’s case acts as not only an electrical but a thermal insulation also, in that it tends to ****** the rate of heat transfer. This is one reason why breakers have wire size ranges marked on them. Too small a wire attached to the breaker cannot adequately aid in cooling the breaker.

The temperature at the circuit breaker’s terminals must not rise more than 50 degrees C. above the ambient air temperature surrounding the breaker. The UL-489 test standard has been used to test many, many circuit breakers over the years and has proven to be a pretty good standard by which the safety of circuit breakers can be determined.

Now LV/MV power breakers you find in switchgear are a whole different story, they are not UL listed they are designed and tested to ANSI C37, whole different concept. They have very high performance standards and are designed to last forever with proper maintenance. Depending on the size and voltage they require an overhaul after a certian number of operations and/or a certian number of fault interuptions.
 

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Under a bolted fault I would. Every bolted high current fault puts the contacts. And in truth a UL listed breaker is only guaranteed at 3 fully rated faults (I think if memory is correct)
Agreed. UL 489 tests MCCBs to open and close three times into their full interrupting rating, after that, all bets are off.

That said, I still think it's a terrible idea. I've seen a single short circuit test blow pieces out of a breaker, and the factory rep argued that was "normal" just as long as the breaker was completely torn-down and repaired after each short-circuit fault. Well, yeah, but what are the odds of that happening? :rolleyes:
 
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