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How to find a defective breaker that won't trip?

Posted by thaugen (My Page) on
Mon, Dec 30, 13 at 13:04

Yesterday I plugged a small 800 watt heater into an outlet and the overhead lights flickered for an instant and then everything was fine. Today I plugged in the heater and the lights flickered and then went off and the outlet wouldn't work either. No tripped breaker. The outlet is on the other side of a stud next to the bank of four light switches. Four-way switches, no idea what feeds what.

All I have to test with is a continuity tester and an outlet tester to verify outlets are wired correctly. The outlet and the switches still have some current present, but the outlet won�t even light a 15 watt bulb. I am guessing a bad breaker hasn�t fully tripped and is still passing a small amount of current.

Two Square D 200 amp breaker panels, about 25 breakers per panel, they�re double-breakers (2 breakers in one slot). Only a dozen of the breakers are marked as to what they feed. I removed the panel covers and checked only to find current at all breakers. My uneducated guess is that a breaker has gone bad and instead of tripping is letting some current still pass.

Thanks in advance for any experienced advice.

Tom


Follow-Up Postings:

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RE: How to find a defective breaker that won't trip?

Start by cycling ALL the breakers at your residence. Move the operating handle firmly to OFF, then firmly to ON.
I do not believe that the problem is a breaker. More likely to be a loose connection in one of the wall boxes of the affected devices.


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RE: How to find a defective breaker that won't trip?

I would suspect that you have back-stab devices in the circuit. They are notorious for failing, especially as they age. These devices use internal spring clips to hold the wires and provide electrical continuity rather than machine screws.
I have seen several phantom failures 'cured' by the act of merely removing devices from their junction boxes, leaving the wires connected. As the wires twist slightly in the spring clips, carbon deposits, which are dues to electrical arcing, are chipped away and continuity is restored. A bad design which is still legal on 15 amp circuits.


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RE: How to find a defective breaker that won't trip?

Thanks for the back-stab tip but these switches and outlet are all wired by screws.

By dumb luck I found the breaker in question, and to rule it bad or good I moved the wires to a known good breaker. No luck, breakers are good, Now it is time to tear into the boxes and try to find a bad connection that is letting only a small current pass.


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RE: How to find a defective breaker that won't trip?

What you describe is a typical bad connection. It is no surprise that the breaker is good. Most people knee-jerk to a bad breaker when this is hardly ever the case.
I wouldn't be surprised if you found an errant failed back-stab.


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