I talked to an engineer at Square D about their failure rate once, while trying to do some reliability calculations for an emergency power system. The company line is that their breakers are 100% reliable with absolutely no failures EVER up to the limit of the UL listing, which requires a certain number of cycles. He wouldn't give me any numbers about their in-house failures. I imagine you'd get pretty much the same story from every supplier. (Well, maybe not FPE)
Every breaker sold has been tested and tripped at least once already, as evidenced by the "tripped" position out of the box. No need to test it again! I look at breakers the same way I look at hard drives- if I have ANY reason, ANY at all to suspect the slightest chance of failure, it goes in the garbage and a new one takes its place. There are some things you just don't dick with.
[This message has been edited by SteveFehr (edited 11-09-2006).]
