Breaker Lifetime

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ykee

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I was wondering how circuit breakers degrade over time, and what I could expect as a reasonable lifetime. I've tried to search for this info, but can't seem to find anything.
 
080502-1928 EST

ykee:

Most breakers will have some sort of mechanical latch. These will have a sharp edge in the latch mechanism. If you operate one of these many times there will be wear at the sharp edge and this rounding will increase the variability in the trip point. This should tend to cause tripping at a lower current. A good fail safe direction.

There will be criteria for minimum and maximum trip points as a function of current, temperature, altitude, humidity, vibration, shock, and so on. Then there will be durability requirements for mechanical switching life, and overload life.

I did some consulting with a breaker manufacture many years ago. One problem was breakers for the B1 bomber were producing about a 10% yield in production. However, these would meet commerical specifications. This was putting manufaturing very much in the red on these units. My job was to find the cause. It was a problem relating to the modulus of elasticity of one component. Solving this increased the yield to 90%.

You have to run a lot of tests on different samples from production to really evaluate a breaker design.

My own personal experience with QO breakers has been very good. But I have never done any testing on them other than some very limited tests at 5000 to 10,000 A DC using a bank of car batteries.

Some 15 A QO units I have used as on-off switches several times per day for more than 40 years with no problem. I almost never trip a circuit breaker except in one case where we have a DeWalt radial arm saw at the end of something over 100 ft of #12 at 120 V with a 20 A QO. This trips if I turn off and on to quickly. Really we should run a 240 V circuit to this location.

I believe many others will suggest that QO breakers are generally good. However, there have been some counterfeit units in the marketplace. Buy them only from authorized dealers.

The QO is essentially a magnetic trip at high current and some sort of i^2*t at lower currents. See Sq-D plots of trip time vs current.

.
 
ykee said:
I was wondering how circuit breakers degrade over time, and what I could expect as a reasonable lifetime. I've tried to search for this info, but can't seem to find anything.
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Cicuit breaker is a very broad term, what kind? I have maintained many 480V and 5kV breakers from the 1940's that are still beter (with modern protective devices)than any plastic cased, cheap alloy junk you can buy new today It is all about the testing and maintenance.

Now little MCCB's, I would say 30 years is pushing it, you can test them, but cheaper to replace.
 
crossman said:
According to some on this forum, a breaker goes bad as soon as you replace the panel with a new panel.
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Because the symbiotic relationship has then been destroyed. :D
 
breakdown

breakdown

I did a remodel job (apartments) 4 buildings, 96 units. They were 40 plus years old. They upgraded everything as far as lighting etc. but insisted on leaving the original panels and cb's?? I was told euipment begins to "breakdown" at the point of installation in a ce class?? Some here did not agree??
 
ItsHot said:
I did a remodel job (apartments) 4 buildings, 96 units. They were 40 plus years old. They upgraded everything as far as lighting etc. but insisted on leaving the original panels and cb's?? I was told euipment begins to "breakdown" at the point of installation in a ce class?? Some here did not agree??
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Anything 40 years old or more is at the end of its life. The testing exceeds the cost of most breakers typically employed in an apartment building, so replacement is suggested.

Square D type QO and Cutler-Hammer type CH both have lifetime warranties. I wonder if you just showed up at the supply house with a box of 40 year old breakers if you could trade them in for fresh ones under the lifetime warranty program? Just say they don't trip at the right time. They'd have a tough time proving otherwise.
 
I would take them back on one condition.
That if the breakers did have a life time warranty at the time they were manufactured I would concider it.
If not, if the manufacturer made the "lifetime warranty retroactive I would consider it.
If the user can prove a manufacturing defect I would concider it.

Just what do I mean be concidering it? I would make the contractor put his money where his mouth is had submit a purchase order for the time thatr is required to test the breakers. That is I would gladly replace any breakers at not charge if in fact they could not pass a factory production test that all breakers manufactured in the facility must pass. That the contractor would be charge for those that did not.

I have replaced numerous common industrial breaker that had a one year warranty that I determined had failed because of a manucaturing defect. On very rare occasion I have seen a breaker that has lost a contact, a braze that failed between the load connector and the trip unit, breaker that have good trip free for no appearent reason such that they are not able to be latched and closed.

I believe that you will find it interesting to note what the rigorous are that MCCBs must ne designed for and pass per UL489 test requirements.
 

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templdl said:
Just what do I mean be concidering it? I would make the contractor put his money where his mouth is had submit a purchase order for the time thatr is required to test the breakers. That is I would gladly replace any breakers at not charge if in fact they could not pass a factory production test that all breakers manufactured in the facility must pass. That the contractor would be charge for those that did not.
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I'd be happy to do that if you could show me any language in the warranty that even comes remotely close to that requirement. Until then, it's up to you to prove that they aren't defective if I say that they are.
 
mdshunk said:
I'd be happy to do that if you could show me any language in the warranty that even comes remotely close to that requirement. Until then, it's up to you to prove that they aren't defective if I say that they are.
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What if they asked for your proof that they were defective?
 
Then if the contractor was so sure of their claim that the product is defective it is a non-problem no risk for the contractor.

It is easy for a contractor to simply keep on replacing product that isn't defective with new product returning as defective until the actual cause of problem if located. From my perspective has not been uncommon. When there is no cost to the contractor there is no risk of loosing money. Such a deal.

I don't believe that it is up to the manufacturer to defend their product and assume the cost of determining if it is good or bad at the whim of a contractor. If the contractor is so certain that a product is defective there should be no risk making "put their money where their mouth is." This makes it a mute point wouldn't you think?

If my product has failed because of a manufacturing and not because of an installation or an application issue and it falls within the warranty period there is no hesitation in replacing it. But, I don't think that I should assume the cost on labor to verify that a product isn't defective or has failed because of a misapplication of being incorrectly installed.
 
templdl said:
But, I don't think that I should assume the cost on labor to verify that a product isn't defective or has failed because of a misapplication of being incorrectly installed.
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Why would you even care? It's not coming out of your pocket. I say this, very simply... the warranty does not make it incumbent on the consumer to prove that it is defective or "put any money on the line". If it did, we'd be having a different conversation.
 
mdshunk said:
When have you ever had to prove anything was defective?
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Never. Of course, I've never brought in a box full of 40 year old breakers and asked for new ones either. That would have to cause some kind of reaction. If not the first time, maybe the second or third time.

Care to try it out for us?:smile: I would really be curious how far you could go with that before getting some kind of reaction from SD or CH.
 
When my paycheck is from the company that hired me the money isn't comimg out of my pocket?? That would be a good disussion to have with a manage, district manager, product line manager, all the way to the top.

Here's a quare D warranty:
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STANDARD WARRANTY: Square D warrants equipment manufactured by it and sold through authorized sales channels to be free from defects in materials and workmanship for eighteen (18) months from date of invoice by Square D or its authorized sales channel. If within such period any such equipment shall be proved to Square D's satisfaction to be non-conforming, such equipment shall be repaired or replaced at Square D's option. This warranty shall not apply (a) to equipment not manufactured by Square D, (b) to equipment that has been repaired or altered by other than Square D so as, in its judgment, to affect the same adversely, or (c) to equipment that has been subjected to negligence, accident, or damage by circumstances beyond Square D's control, or improper operation, maintenance or storage, or to other than normal use or service. With respect to equipment not manufactured by Square D, the warranty obligations of Square D shall in all respects conform and be limited to the warranty actually extended to Square D by its supplier. Non-conforming products must be returned at Square D's expense for evaluation unless this is waived in writing. Replacement products may be new or reconditioned. The foregoing warranties do not cover reimbursement for labor, transportation, removal, installation, temporary power, or any other expenses that may be incurred in connection with repair or replacement.
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I also attached a couple of C-H warranties.
 

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mdshunk said:
Anything 40 years old or more is at the end of its life. The testing exceeds the cost of most breakers typically employed in an apartment building, so replacement is suggested.

Square D type QO and Cutler-Hammer type CH both have lifetime warranties. I wonder if you just showed up at the supply house with a box of 40 year old breakers if you could trade them in for fresh ones under the lifetime warranty program? Just say they don't trip at the right time. They'd have a tough time proving otherwise.
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Interesting. In all of my years working in the trade, i have never heard that anything 40 years old is at the end of it's life. I used to have a guy that would go around telling my customers that 20 years was time for a panel change. Needless to say, he no longer works for me. As far as showing up at the supply house with a box of breakers, i worked the counter at one some years ago, and if that happened to me, i would have shown you the door.
 
I'm more concerned with a simple panelboard full of 15 amp breakers. I'm trying to figure out if it is worth replacing in a renovation (money's tight.....isn't it always?). My gut say replace the breakers, but I can't really justify it, other than by saying the breakers are old.

To me, it would seem that the lifetime of the breaker would be determined by the number of operations & by heating.. So, if a 15 amp breaker has been used normally not at the max load, it should last pretty much forever.
 
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