Electrical – Could a circuit breaker ever be faulty in a way that prevents it from tripping

electrical

I know that sometimes a circuit breaker will be faulty and will not pass power, but I have a situation where I identified a wiring problem where I expected the breaker to trip but it didn't. Is this possible? How can I test that my breakers will trip when a fault is detected?

To explain the situation a bit better: I had a circuit where three outlets worked, while one was faulty and a switched set of lights didn't operate from the switch. When I investigated the faulty outlet I found a stray wire that had pulled out from the back. I removed the outlet completely and rewired the broken electrical chain together. To my surprise, the lights started to operate correctly.

If there was a fault in that outlet, why didn't the breaker trip? What conditions must be met to trip the breaker? I'm pretty sure a live-to-neutral short would trip it, but what about live-to-ground or neutral-to-ground?

Maybe the fault was something other than a short? I can't really fathom what the actual wiring could've been to have caused the symptoms that I observed. If memory serves correctly I believe it was a white neutral wire that was loose. My non-contact voltage sensor indicated that both slots of the outlet were hot.

Best Answer

Neutral to ground will not blow a breaker. Live to neutral or live to ground should.

It is possible for a circuit breaker to fail to trip. This is a huge concern with old Federal Pacific breakers - some were recalled due to not tripping in a fault, and could cause a fire. Testing for it isn't really a safe thing to do - because if your breaker has failed, intentionally shorting it could cause a fire.

My guess would be that your breaker is fine and there was no short - one wire for the outlet had come disconnected. You said you wired the chain together after removing the outlet - that chain was broken with the wire missing, so any outlets downstream of that didn't get any power.