Well this house i went to was about 30 years old . The main breaker had blown so they wanted me to replace it,i did. 1 month later it done it again i went theire and reset it. the house isnt overloaded what could it be????????????

It sounds like there could be a serious ground fault that only occurs because of a specific load coming on. Meaning, is it possible that this occures right after the homeowner turn on a large load like a pump motor or heater unit? If the ampere reading with typical loads on is not near the OCD rating, this is the only thing I can think that could be causing this to happen.

Stan,

How about vibration?
Anyone banging on the walls near the panel?

Bill

gravity then what should i do im in a mess???

Stan: Is this a bolt-on main breaker, or is it a plug-on? Any signs of overheating around it?

Mike (mamills)

I too would look for signs of heating, the only times I have seen a branch circuit fault take out a main, the branch breaker had also tripped, but it might happen.

Are you sure of the connected load?

Have you checked your amp-clamp against a known load to verify it is working properly?

Back to the vibration thing. I have seen several times where vibration had tripped the main. Once or twice when siding was being done and once when when a roof was being redone above the panel.

Was any construction being done?

Bill

[This message has been edited by Bill Addiss (edited 04-22-2003).]

Stan, I take it that none of the circuit breakers had tripped except for the main breaker?

If one of the circuit breakers is faulty and won't trip, the main breaker will trip instead if there is a short in the branch circuit.

A remote possibility that comes to mind is that there is a ground fault or short circuit soon after the branch breaker resulting in a very high current. The new main breaker responds faster than the old branch breaker. However, this doesn't explain why the old main breaker blew.

well guys thanks for the ideas,in the morning im going to see if any of the branch circuit breakers are faulty.By the way no vibrations can occure its on a basement wall. thanks guys

What brand panel? FPE breakers are well-known to not trip if there is a fault...