Breaker tripping - how to troubleshoot?

[bw77]

For the past week, one of the breakers has been tripping.
When it trips I reset it, and it stays on for varying lengths of
time from 2hrs to 48hrs.

House is 45 years old, in the country. Single story with a dry basement.

Panel is in the garage. Cable goes up into the attic, then along the
wall for about 10 ft, then down through the wall into the basement.
I would like to look at the cable in the attic to check for damage, but there is little headroom.
The roof slopes down to that wall, and I can't get in there. Maybe I need
to try harder. Maybe put down some plywood to slide myself in there
and try not to get a roofing nail in my head.

There is only 1 outlet in the basement, nothing plugged in at this time.
There was a freezer there, but I moved it when the problem started.

20A circuit. I replaced the breaker and no change in behavior.

What kind of fault would cause this? If there was rodent or nail damage
wouldn't the breaker trip right away?

 

[Dumber than lumber]

What else is on that 20 amp circuit? Could be a bad outlet or bad fixture.

 

[rancherbill]

My only thought is that there's another outlet or light somewhere that you don't know about. It also may be the actual receptacle has failed or it's wire connection.

 

[sparky 1971]

Pull the receptacle out of the box. I've seen it more than once where the outlet got crammed into the box and the ground wire folded over right next to the hot terminal. Over the years, vibrations got them close enough that contact was made and it shorted. Also, if it is a metal box, especially a handybox, make sure the hot terminal isn't touching the side of the box. If the breaker is a gfci, it could be the same thing with the neutral.

 

[Dagny]

Get someone with a megger. These situations are where fires start. Leave it off till you find it.

 

[Terry D]

Are you sure there is nothing else on that circuit besides that one receptacle.

 

[bw77]

Are you sure there is nothing else on that circuit besides that one receptacle.

I put a toner on the circuit and I could not find any other devices.
The lights are on a different circuit.

I pulled the receptacle out and it looked good. I checked for connectivity
between the hot/neutral and hot/ground and there was none.

I left the breaker off. I expect to need an electrician.

Thanks for all your comments.

 

[Terry D]

I put a toner on the circuit and I could not find any other devices.
The lights are on a different circuit.

I pulled the receptacle out and it looked good. I checked for connectivity
between the hot/neutral and hot/ground and there was none.

I left the breaker off. I expect to need an electrician.

Thanks for all your comments.

Its hard to diagnose the problem over the internet on something like this. Its not a direct short if its not tripping instantly. If you are sure there is nothing else on that circuit, besides what sparky1971 has suggested, i have seen a staple that was hammered in to tight and took all those years to start causing problems.

 

[sparky 1971]

Just for fun, disconnect the receptacle. Cap or tape the ends of the wires real good and turn the breaker on. Leave it that way for a couple of days. If the breaker trips again, look high and low for something you may have overlooked that may not be working. If after that, you are 100% sure there is nothing else on the circuit, it's probably time to abandon that wire and run a new one. You can pay someone to come out and tell you the wire is bad, but you will already know that.

 

[wyliesdiesels]

You havent said whether this is a regular breaker or a GFCI or AFCI...

 

[bw77]

You havent said whether this is a regular breaker or a GFCI or AFCI...

Regular breaker.

 

[Fierljeppen]

The first thing you need to do is throw an amp meter on there and see how many amps you're drawing. You need to establish whether it's a load issue or an intermittent hot-to-neutral/ground. While you're at it, check the voltage at the receptacles on that circuit.

If you don't have an electrical meter or don't feel comfortable with doing this, get a qualified friend or hire an electrician. Since you've already replaced the circuit breaker and are experiencing the same results, I'd keep that circuit locked out until you're able to diagnose and repair it.

 

[bw77]

The first thing you need to do is throw an amp meter on there and see how many amps you're drawing. You need to establish whether it's a load issue or an intermittent hot-to-neutral/ground. While you're at it, check the voltage at the receptacles on that circuit.

If you don't have an electrical meter or don't feel comfortable with doing this, get a qualified friend or hire an electrician. Since you've already replaced the circuit breaker and are experiencing the same results, I'd keep that circuit locked out until you're able to diagnose and repair it.

I had an amp clamp on the hot wire going into the breaker this morning.
Zero amp draw. I checked several times, and then the breaker
tripped after 2.5 hrs. I never saw any current on it.

I reset the breaker, still zero current.

 

[PFSard]

Just out of curiosity. If you have another breaker the same rating. What happens if you swap breakers?

 

[rsparks64]

Some breakers only last a few years, maybe 3-5, and start going bad. Could be your breaker that is the problem.

 

[bw77]

Some breakers only last a few years, maybe 3-5, and start going bad. Could be your breaker that is the problem.

It's a new breaker.

 

[Fierljeppen]

I had an amp clamp on the hot wire going into the breaker this morning.
Zero amp draw. I checked several times, and then the breaker
tripped after 2.5 hrs. I never saw any current on it.

I reset the breaker, still zero current.

Good information...With the power off to that circuit, you could check for ohms across the hot and neutral, you should not read any ohms at all. If you decide to power up that circuit, see if the circuit breaker housing gets warm at all.

An intermittent short-to-neutral/ground is much more serious if your wiring isn't enclosed in steel conduit. Please keep that in mind, my main concern for your situation is an electrical fire. I don't mean to be an alarmist, but you need to understand that an electrical short-to-ground can create a very hot spot before the circuit breaker trips. The amount of amps in a short-to-ground is exponentially higher than the 20 amp circuit breaker.

 

[bw77]

Good information...With the power off to that circuit, you could check for ohms across the hot and neutral, you should not read any ohms at all. If you decide to power up that circuit, see if the circuit breaker housing gets warm at all.

I just measured 100K ohms across hot and neutral. Bad cable?

 

[wyliesdiesels]

It should read open/no continuity.

 

[Fierljeppen]

I just measured 100K ohms across hot and neutral. Bad cable?

Nice work, you found the problem. As far as what's causing that, it's hard to say. It could be frayed wire insulation, penetrating staple / nail, compromised receptacle, etc...

Next step would be to inspect your wires by disconnecting them in sections, from the panel to the last receptacle, using your ohm meter the entire way. You'll eventually find the problem and be able to make a necessary repair.

Nice job! I'm very confident at this point that your going to be successful in your electrical endeavor.

 

[Shiftless]

I don’t understand how a resistance of 100,000 ohms would lead to tripping the breaker.

 

[BillK]

I just measured 100K ohms across hot and neutral. Bad cable?

Is that with the wire still attached to the breaker ? If so take it off the breaker and see if it stays the same.

 

[Fierljeppen]

I don’t understand how a resistance of 100,000 ohms would lead to tripping the breaker.

100K ohms wouldn't lead to tripping the breaker, but it's shows that the electrical wiring or devices are compromised. The ohm reading was done with no potential on the wires. The problem is that at some point the 100K ohms become much lower when there is potential on that circuit. It may even become a direct short-to-ground, which becomes the most serious situation.

Did I answer your question?

 

[Shiftless]

Did I answer your question?

Yes, you did and Thanks!

 

[Shiftless]

(deleted)

 

[SlappyWhite]

It sounds like a bad cable. As others pointed out it could have been a staple etc. It could have also been rodent damage.

Since it is a dedicated run panel to one outlet if you still need the outlet in that location just run a new wire. Where the damage is on the wire is a moot point beyond enlightenment as you should not cut and splice it and end up with a buried splice in the attic etc.

If you don't need the outlet there now, disconnect it and you just freed up a breaker spot for something else...

 

[Walkers]

My guess is a bad out let or a wire nut issue. Pull the cover plate off and pull the outlet out, and post some pics.

 

[bw77]

My guess is a bad out let or a wire nut issue. Pull the cover plate off and pull the outlet out, and post some pics.

I pulled the outlet, removed the wires and tested for resistance on the pulled wires.

 

[rancherbill]

deleted

 

[JeffinIdaho]

Carefully inspect the power cord that looks like a chew toy to the dog.

Oh wait…that was my problem.

 

[Walkers]

I pulled the outlet, removed the wires and tested for resistance on the pulled wires.

Gotcha. Any other J boxes in between?

 

[Dagny]

Sometimes wires or other things will get a carbon track. Engine people will be familiar with it cause it happens more with higher voltages. I don't know for sure but suspect moisture or some other conductive substance gets a little current flowing and creates a semi conductor. Carbon is a strange element it's resistance goes down as it warms. A track can conduct a small current that gradually increases then an arc occurs and trips the breaker.

 

[sparky 1971]

If there is nothing else on the circuit and it wasn't the unlikely event that it was a bad receptacle, my guess is that it will be one of two things. 1) A staple was driven in too far and over the last 45 years has finally (barely) worn through the jacket and insulation. 2) When the wire leaves to go to the basement, it got yanked into a corner of the roof framing and as the house has settled, has pinched the cable and worn through the jacket and insulation. In either case, it isn't worth fixing. Just run a new wire.

Did you leave the breaker on with the receptacle disconnected? If so, has the breaker tripped again?

 

[MoonRise]

The wire/cable is 'bad' somewhere. The wire, a staple/nail nicked it, etc.

Either trace it (section by section) or just replace it.

(my cable/breaker weirdness was when some new wiring with a new breaker insta-tripped with a LOUD bang when first energized. Check for anything obvious on the circuit, reset the breaker and energized again. Insta BANG. Check again, more closely, found nothing. Reset breaker and energized. BANG. I don't remember how many times I did the check-reset-BANG cycle until there was yet another BANG but this time with a relatively small flash of light right by the outside of the panel. Shut the panel off, look closely and find a 'slight' carbon scorch mark on the outside off the panel where the branch circuit NM-B cable exited the panel. Removed the cable clamp holding the cable in the panel knock-out and there was a factory burr/splinter on the inside of the metal clamp body that just HAPPENED to line up with the HOT wire in the NM cable. When everything was installed and tightened, that sliver punctured the outer NM insulation jacket and the inner hot wire insulation and created a dead-short through the clamp body to the panel enclosure. If the sliver had hit the neutral or ground, it wouldn't have tripped. Removed the sliver, cleaned things up, energized things and all good.)

 

[bw77]

Did you leave the breaker on with the receptacle disconnected? If so, has the breaker tripped again?

It's been on for 24hrs without tripping. Maybe just a bad receptacle? But no signs of arcing or odor.
If it stays on a few more days I will replace the receptacle.

 

[Terry D]

It's been on for 24hrs without tripping. Maybe just a bad receptacle? But no signs of arcing or odor.
If it stays on a few more days I will replace the receptacle.

I don't think if I have ever seen a receptacle go bad in that way, not saying it cant happen. Is there a actual ground wire? Could it possibly have been close enough to the hot screw to cause tripping, you would probably see some kind of mark on the wire though.

 

[Terry D]

I don't think if I have ever seen a receptacle go bad in that way, not saying it cant happen. Is there a actual ground wire? Could it possibly have been close enough to the hot screw to cause tripping, you would probably see some kind of mark on the wire though. I know sparky1971 already suggested this, Is this a standard or GFCI breaker? Is this a standard or GFCI receptacle.

 

[sparky 1971]

I don't think if I have ever seen a receptacle go bad in that way, not saying it cant happen. Is there a actual ground wire? Could it possibly have been close enough to the hot screw to cause tripping, you would probably see some kind of mark on the wire though.

It's a long shot that the receptacle is bad. I have seen a bad receptacle cause the breaker to trip but there has always been a visible problem, and, more often than not, the receptacle came out in several pieces once the plate was taken off.

A picture might help but won't change anything. I am envisioning a piece emt and a handy box on the basement wall with romex in it. If that's the case, it's more likely that the hot was barely touching the box or the 6/32 screw didn't get cut off, hit the pipe connector and bent down and into the romex. I have seen both of those happen. Of course, there is still the potential that the wire is bad.

 

[nadogail]

I don't think if I have ever seen a receptacle go bad in that way, not saying it cant happen. Is there a actual ground wire? Could it possibly have been close enough to the hot screw to cause tripping, you would probably see some kind of mark on the wire though.
[/QUOTE)
I have found receptacles (Outlets) broken and shorted because someone shoved furniture into a plug that was plugged into the outlet. A table or a couch when pushed sideways into an inserted plug can "do a number" on a receptacle.

 

[bw77]

I replaced the receptacle, plugged in the freezer and the circuit has stayed
up for over 24hrs. So either the receptacle was bad (no signs of that) or
something I did in the process of replacing it fixed the problem.

It's in a finished area of the basement, so it looks like any other part of the house.

Thanks to everyone for your advice and comments.

Here's the long version:

20A circuit in finished basement area with 7 duplex outlets. Freezer plugged
into an outlet in the middle of the circuit. Lamp plugged into the last outlet on the
circuit.

Circuit breaker started tripping at various times.

I unplugged the freezer and the lamp, no change (NC).

I replaced the breaker, NC.

I located the first outlet and disconnected the downstream wires, NC.

I disconnected the wires from the first outlet, circuit did not go down (4 day test).
Indicates bad outlet.

I replaced the outlet, connected the downstream wires, plugged in the freezer,
circuit has been up over 24 hrs. Fingers crossed, I hope this is the end of the
story.