Circuit breaker trips intermittently; causes?

**thaddeus cox** · 10-30-2012, 08:32 PM

Hey all - let me start by saying that I already know you're all going to say "have it evaluated by an electrician"... and rest assured that this is going to happen ASAP.

However... as an academic exercise, what do you suppose is the cause?

The situation: my mom has a circa 1970 single-level ranch with copper wiring... no Al if that's what you're thinking. A month or two ago, she came home from vacation to find that her DVR was off (and she had missed recording some of her shows) because the circuit breaker had tripped.

Since then, the breaker tripped for unexplained reasons a couple more times, so she had the breaker replaced, thinking it may have worn out.

Well, a couple days ago it tripped again.

This circuit is probably one of the most used in the house as it serves the living room and front porch light, but I doubt it ever sees anything near it's rated capacity. It's been performing just fine for decades, and nothing at all has changed in recent memory as far as we know.

Any guesses on the possible cause?

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**John Kogel** · 10-30-2012, 09:08 PM

A rodent has taken up residence and has chewed thru the insulation of the wiring.

A connection, maybe at a back-stabbed receptacle, has gotten loose from overuse or it has gotten corroded.

A water leak has soaked a connection and caused corrosion.

An electrician might be able to narrow down the location to confirm which it is.

Garry Blankenship · 10-30-2012, 09:47 PM

The possibilities are many, but since you replaced the breaker the problem is elsewhere in that circuit. This has been argued B4 on this forum, but I feel wiring through receptacles, ( rather than splicing out to them ), is a bad situation. Particularly bad, if quick wire / stab loc terminations are in play. My first guess is that you have a bad contact at a stab-loc termination at a receptacle in that circuit.

**Chris Weekly** · 10-31-2012, 04:48 PM

Back stabbed receptacles would be my guess, too. I had a house once with this similar problem and after some discovery work, finally found the culprit, made corrections and no problem afterward. Let us know the final outcome or your moms situation.

**thaddeus cox** · 11-01-2012, 11:42 AM

Thanks for the replies all.

So what exactly could be happening inside the back-stabbed receptacles? An intermittent short or just a loose connection? Could a loose connection make the breaker trip?

Seems like anything significant enough to trip the breaker would also make itself evident in the behavior of the equipment connected (TV for example), and at least once she was sitting right there watching TV when it tripped, and she said nothing unusual happened other than the power going off.

**Harry Janssen** · 11-01-2012, 05:23 PM

Could a mouse,or other rodent chewed on the wires,some thing had to have changed to caused the trip.

**Greg Filian** · 11-01-2012, 06:03 PM

Originally Posted by thaddeus cox

Thanks for the replies all.

So what exactly could be happening inside the back-stabbed receptacles? An intermittent short or just a loose connection? Could a loose connection make the breaker trip?

Seems like anything significant enough to trip the breaker would also make itself evident in the behavior of the equipment connected (TV for example), and at least once she was sitting right there watching TV when it tripped, and she said nothing unusual happened other than the power going off.

Possibly both, a loose connection would cause an intermittant short. Wire heats up and expands the more appliances being used. Conversly it shrinks when it's cold. Copper does it much less than aluminum, but it still happens. Your electrician will need to open each outlet check the wire connections and rule them out as the source of the problem. I'd start there because it may be the easiest place to start.

**Chris Weekly** · 11-01-2012, 06:08 PM

So what exactly could be happening inside the back-stabbed receptacles? An intermittent short or just a loose connection? Could a loose connection make the breaker trip?

The wire could work its' way loose on those back stabbed outlets. The connection is relatively poor to begin with, and as the electrical cords are inserted and pulled out, this gives more opportunity for the wires to loosen from the pinch connectors in the outlet. Loose wire, poor connection, arcing or sparking sending a signal back to the breaker, and the breaker is there and is doing its' job - detects a problem, and trips the power. Your job is to find the culprit and fix it, or to call your electrician and let him find it and fix it.

**thaddeus cox** · 11-01-2012, 06:21 PM

I guess what I mean is... "should" an intermittent/loose connection cause a conventional breaker to trip? I thought that was the reason we have AFCIs, and that conventional breakers should only trip magnetically (due to *large* overcurrent) or thermally (due to lesser overcurrent).

Is the theory here that a loose connection would trip the magnetic protection?

Thanks again, just trying to learn here.

PS, I sure hope mom's house doesn't have backstabs... after all I've read about them here, I'll probably end up replacing them all if so.

**Eric Barker** · 11-02-2012, 08:56 AM

Originally Posted by thaddeus cox

Hey all - let me start by saying that I already know you're all going to say "have it evaluated by an electrician"... and rest assured that this is going to happen ASAP.

So while you're waiting to call for the electrician and going through all possible scenarios I strongly recommend keeping the power off for that circuit. The breaker is telling you that there is a problem - don't ignore it by constantly turning the breaker back on.