Is there a lifetime failure count for a breaker?

Question

I have an external cutoff for my air conditioner that has two physical fuses (TR-50's, time delay 50 amps) outside. This is between the condenser unit and the main power panel, where it is protected by a 50 amp circuit breaker.

An electrician is coming to replace the cutoff (containing fuses) with a simple lever cutoff.

In discussing this he said that a circuit breaker should not be allowed to trip more than 4 or 5 times before being replaced.

That struck me as odd. I have never experienced a need to replace a breaker, and some in my house due to stupid wiring patterns (a plug we use for a kettle is on the same circuit as the plug my wife uses for her hair dryer in the washroom) have tripped more often than 5 times.

I am trying to decide if he trying to upsell me, or has a valid point.

Answer 1

Breakers do wear out, and do fail, but without looking it up i would say that wear is not an issue until hundreds or thousands of trips. When they fail, they almost always fail open anyway. I have seen dozens of failed breakers, and they always fail open. Each breaker is tested several times at the factory, and one that has tripped few times in the field is probably more reliable since this type of device has higher failure rate at the beginning and end of life, with most reliable service after some use. Lifetime is not determined just by number of trips, but by how hot it gets for extended periods and, of course, it is working hardest just before it trips so if the circuit is overloaded but rarely trips the breaker is working harder than one that trips regularly due to short overloads.The former sounds like your situation so i would replace just to avoid nuisance trips in the future. Breakers are cheap.

Also, very old breakers have less stringent standards than new ones, depending on national electrical codes so for very old breakers it is always a good idea to upgrade when doing a major rewire.

Finally, when breakers do start to fail they often start to become too sensitive and trip at lower than rated current so if it trips a few times even though it looks like circuit is not overloaded its a good idea to change the breaker.

Answer 2

I've sold breakers for 25 years and never heard of it, but it doesn't make it untrue. Weigh the difference in the price he is charging you to put the breaker in now against what it would cost to have him come back and change it. Then compare your savings. No savings means don't do it until you start having problems.

Answer 3

I don't know. But I've had two breakers fail, both of which had tripped many times (including an exciting "fail closed"--luckily while I was standing there with the breaker box open and could pull the master switch).

It may have depended on the build quality of the breakers, or there may have been other problems. The wiring in that house was quite dodgy.

Answer 4

I find this hard to believe, but it may be true in the "worst case" of a dead short.

A breaker has an electromagnet in it, that when a certain amount of current is passing through, causes the spring-loaded contacts to release. Therefore, best case, it should last as long as a relay -- it is an anti-relay, in a sense.

Now if you have a hard short, that may stress the electromagnet for the 200 milliseconds or so it is absorbing the extra current, and that may reduce its lifetime. Breaking a high-current load may also pit and burn the breaker's contacts.

Contrast this with plugging in one too many appliances, where the electromagnet is operating well within design parameters -- it should last nearly as long as an ordinary wall switch in this case.

I think he's trying to up-sell you. Contact the manufacturer of your circuit breakers for the definitive info, and if they don't back the electrician up, report him to your local better business bureau.