I had a customer call with a breaker melted to the bussbar. this was the second or third breaker that has done this according to him.the bussbar was fine but the breaker fell apart I installed a new breaker and it made good tight connection and the amp load was in range. any Ideas? I think it was a g&s panel with challenger breakers.
Load up the circuits and check the voltage drop from the feed conductor to the load conductor terminations. You'll be looking for voltages around 100 ma on the low end to about a volt, depending on the load and the size of breaker. Compare readings for the various breakers for an idea about what is normal in that panel. If the voltage drop seems high, move the probe from the feed wire to the bussbar by the breaker, then the metal part of the breaker.
It's the equivalent of checking the temperature of the connection points, but it's faster and easier to pinpoint the problem because voltage drop doesn't migrate the way heat does.
Do you have a non contact thermometer? They are getting cheap enough for the mortal man and will let you further track down this heat thing. TWH is right about starting with your meter to see where the leak is.
thanks for the input. The bussbar was damaged from a previous breaker but the breaker I removed did not appear to have damaged the buss.I did sand the buss and applied corrosion inhibiter with the new breaker. The breaker is feeding 15 kw heat strips and is pulling 60 amps on each leg.
Since your load is linear my idea that it may be related to non linear loads is not going to explain it. A 3 phase 15 KW load on a 60 amp breaker should be around 42 amps so the breaker looks correct for 3 phase, Single phase would be a 90 amp breaker and a 72 amp load, Note that the 90 amp breaker is actually 1/8th of an amp too much load for the 90 amp breaker but most inspectors would give that much away.