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viper 04-03-2011 09:06 PM

Heating question on main panel breaker, 15A
OK, rather simple question here. I am experienced with electrical but never have run into this. In a federal pacific box, we have a 15A breaker that is running the squirrel motor for the HVAC. It runs a lot. Amperage FLA is 7.4A which is perfect for the load and there are no concerns of the motor having problems, heating up, and over drawing.

Everything points to a problem with the breaker or the termination. As most of you probably know, these are called "stablok" style breakers and I am not a fan but never had this problem. Basically the breaker is heating up and tripping from heating but is far from exceeding the 80% continuous rating of the breaker.

Thoughts? I guess at least the breaker is working but this most certainly is a problem both in terms of safety and nuisance trips.

a7ecorsair 04-03-2011 09:19 PM

Have you actually measured the circuit current?
Any chance you could swap the breaker or move the wire to a different breaker as a test?

viper 04-03-2011 09:27 PM

Yes, actual load current was tested. I was actually doing some true kw/h testing earlier today and noticed the breaker was warm. I highly suspect the stupid contacts but wondering if that is usually the issue of if something internal in breakers would do this? Yes, I will probably try to divert the load for testing.

Just Bill 04-04-2011 07:01 AM

FP breakers/panels have been suspect for a long time, source of many unwelcome fires. Probably best to replace it.

AllanJ 04-04-2011 07:25 AM

A breaker should never heat up.

Flip the breaker off, unsnap it from the panel, and inspect the fins underneath (both under the breaker itself and in the pane slot). If there is discoloration or deformation or if the breaker fits on loosely then it may be necessary to stop using that slot in the panel and/or replace that breaker.

If there is no discoloration or deformation in the contacts underneath and the breaker is heating up, replace the breaker anyway.

nap 04-04-2011 07:31 AM


AllanJ;622906]A breaker should never heat up.
that isn't true. Part of the function of a thermal/magnetic breaker is activated by heat. Breakers will get warm when used and the closer to max load, the warmer they get. That is how they function.

Now, in this situation, it is apparently getting warm enough to trip although it is running well below max load. I would suspect the breaker is simply worn out. It could be a problem with the interface between the breaker and the bus and I surely wouldn't exclude the possibility and check it out but, due to the age, I would tend to suspect the breaker itself is the problem.

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