Archive

Posts Tagged ‘signs of corrosion’

Disaster Replacement Circuit Breakers

June 25th, 2010 Comments off

An engineer called MIDWEST and asked how he could make sure a replacement for one of his old obsolete circuit breakers was not something out of one of the US disaster areas. He said it was a used replacement circuit breaker, but it looked shiny as new and seemed to operate okay. But he just had a bad feeling. To MIDWEST, that means he knows something he isn’t telling us. Regardless, here’s the short answer to his question. If you are qualified, remove the cover from the circuit breaker. Remove the arc chutes. On old circuit breakers, be careful, because the arc chutes may fall out in a dozen pieces. Remove the lugs.  Carefully remove the trip device.  Be sure not to lose any barriers or arc dividers. Then a close visual inspection must be made to detect any signs of corrosion or contamination on the breaker operating mechanism or inside the circuit breaker trip device or under the current carrying components. If the breaker got wet, corrosion should be easy to spot, but be sure to make a hard focused inspection.  Something more than a cosmetic look. During this process, look for signs that someone else has already tried to recondition the circuit breaker. Just cleaning a used or even a new circuit breaker, after it has been immersed in water, can be nearly impossible. There will be corrosion and dirt, even mud, in areas that are inaccessible. The trip device must be taken apart. MIDWEST has experience repairing old trip devices. It usually just isn’t worth the time. And if you mess with the trip element, there is a whole sequence of over current tests that must be performed afterwards. You can’t take a trip device apart, put it back together, and not completely test the circuit breaker afterwards. So, if you suspect an old, obsolete, or new circuit breaker has been exposed to water or mud, your best decision might be to destroy it and then throw it in the trash. Note, we strongly encourage destruction of any circuit breaker that is defective, so no one tries to reuse it. If you find nothing to indicate the breaker was damaged, then you have to put it all properly back together and test it.