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Stumped on this Service Call

10K views 68 replies 33 participants last post by  Smoke 
#1 · (Edited)
No, this isn't a "Solve This Service Call", since this one has me baffled.

Went on a call yesterday for a tripping breaker in a house. Fluke 33 read 2.86 amps max, and it was tripping within 2 seconds of turning on. I swapped the breaker out (Siemens 20a), and it held for at least 45 minutes, with 2.23 amps maximum.

"Bad breaker, ma'am. Cash or check?" I wished they were all this easy.





Customer calls late last night, saying the breaker tripped again.

So I head there this morning.... breaker is still in tripped position. I pull the cover off and hook up my Fluke 289 this time. Start recording, then start hunting down what's on the circuit.

The NM comes out of the panel (in a garage) into the basement. Right inside the basement, it splits into 2 runs (yes, there's a box!). One run goes up into the living room, and serves only one duplex for the TV/VCR/DVR. That whole combo pulls 1.2 amps when running.

Other NM goes into a sunroom that was added years ago. 3 receps, two switches, 1 ceiling fan. I pull all the devices and the fan and don't see any nicked wires or grounds too close to hot screws. Nothing that even remotely resembles a problem. One switch in the sunroom turn on the fan light (the fan is on the pullchain), the other switch feeds a post light in the back yard, but turning it on didn't do anything.


After an hour and a half of rooting around this hoarders' house (not packed to the rafters, but the floor is there somewhere), I finally gave up. Told the HO to see what happens.



I shut off the meter, saved the data, and here's what it looks like:



The spike on the left is when I checked the amp reading on the main line coming into the house, just to make sure it was reading amperage correctly... then I clamped onto the branch circuit where the highest peak after that is about 2.5 amps.

Other than the possibility of a buried box, I exhausted my storehouse of experience on this one. I'll admit.... this one got me.
 
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#3 ·
What type of wiring system..BX..Romex..?
All NM.

Did you check the splices in the box..?
Yes.

Do they have any space heaters that they may be using?
None.

The run going to the post light is that UF cable going out there??
I thought of that, but it wasn't turned on when the breaker tripped yesterday. No one was home. Turning it on only caused the amp draw on the circuit to go up a little.
 
#7 ·
It was plugged into an extension cord run in from the dining room for most of the time I was there. The last 20 minutes of the recording is the electronics running when I plugged them back into the recep behind the TV.

It that stuff's the problem, then it should trip the dining room circuit as well.
 
#8 ·
Ok i see that it nm cable .. and its a hoarders' house :eek:

Did you have a clear veiw of all the recptacals?
yes, if I spend 10 minutes clearing the stuff away. I pulled them all out and checked for nicked wires / grounds curled up towards hot screws....

Maybe the wire that leeds to the pole light has an out door recptacle on it.
I turned it on, and that didn't cause it to trip. I never did get the new breaker to trip.
 
#9 ·
This sounds like a buried wire, with a bad spot that causes an intermittent short.

Look again for any other buried wires (shed, or even under that sunroom) ...

I've seen room additions with the wires laying on the ground underneath.
 
#10 ·
I have seen some sun rooms that the wiring is under the decks. There could be rodent damage under there. I also had a romex that was shorting out due to a romex connector to tight where it exited the panel and it was hard to finally catch.

If its a metal roofed sun room the wire in the roof would be really suspect to me also.

One other thing maybe off the wall are the opposing breakers in the panel getting hot and causing a thermal trip?
 
#12 ·
Water condensing above fan and dripping down into fan switch?

Happened to me and the fan also had a remote. Came home to one fan slowly spinning. Each drip caused it to start on low speed and then cycle off.
Turned wall switch off and found just a small trace of water in fan housing.
But this was after several trips of the breaker over a few weeks.
 
#17 ·
After swapping the breaker yesterday, I thought I had the problem solved.... no need to TS any more.

That's the first thing I tried this morning..... divide and conquer. No tripping.

The sunroom has a wood floor, no attic. I can see there being NM underneath it getting wet & going bad. But there's no access under it at all. Nor is there an attic. The whole thing is cheaply made, even plywood walls.
 
#18 ·
Short

From what you said. up to 2 sec and intermittent at night, I would have to go with something far out on the circuit (Pole Light) and settling of soil/Animal (noctural chewers). I love and hate those jobs. Process of elimination. I'd disconnect the hot leg to post first for one night in case someones lying to you.

Photocell?

Is anything on a timer??
 
#19 · (Edited)
From what you said. up to 2 sec and intermittent at night, I would have to go with something far out on the circuit (Pole Light) and settling of soil/Animal (noctural chewers). I love and hate those jobs. Process of elimination. I'd disconnect the hot leg to post first for one night in case someones lying to you.

Photocell?

Is anything on a timer??
2PM isn't really night.

No photocell or timer that I know of.

Not that I'd call it lying,... I'd call it Not Really Knowing.
 
#20 ·
It wouldn't surprise me if the HO isn't telling the whole story. Perhaps they plugged in a space heater or something else that is causing the problem. Obviously you are talented enough that if you can't figure it out from there we can only guess at the multitude of possibilities.

Doesn't sound like a short as the readings would be higher. An intermittent short will drive you nuts. I would see what happens then I would split the circuit for a day or so and see if it's ugly face appears. At least that will get you going in the right place.
 
#21 ·
I don't do residential work, but I would think the only thing you can do would be to trace the circuit box to box. Pull out every device in every box for inspection and then megger the circuit.

???
 
#23 ·
I don't do residential work, but I would think the only thing you can do would be to trace the circuit box to box. Pull out every device in every box for inspection

As far as I can tell, I've done that.

and then megger the circuit.

???
Without knowing 100% sure I've disconnected all the loads, I don't want to risk burning something up.
 
#22 ·
I specifically asked about space heaters this morning.

The sunroom is unheated, and is closed off with the original patio door. I looked around and found no heaters.

I suspect I'll get another call tonight. If so, I'll go back and take the sunroom off the circuit and see if that holds over the weekend. They don't use that room anyway (crap, they can't use that room.... too much stuff!!!)
 
#32 ·
Got back from a simular one today, dead short on breaker after periodic tripping recently. First I temporarily reversed polarity at panel and breaker stayed on, then reviewed circuit contents, found front pagoda lights, disconnected and restored polarity, breaker stayed on. Ohm tested each light box found a splice out wire with daed hot to ground short. All solved in less than an hour. Spent more time listening to retired detective customer talk about frame up conspiracies.
 
#34 ·
My bet is the sunroom, since the TV recep is easy to see (it goes between the joists above a finished portion of the basement, but I can see it down the space when on a ladder).

The sunroom does not have any access under it, no attic, and the walls are finished. If I can narrow it down, I may end up just abandoning a portion of the wiring as I doubt the HO will want to pony up to fix it.
 
#35 ·
More

Sorry, I like this stuff.

Here's what I would do.

Run a temp circuit, couple staples and feed one of 2 branches in basement jbox.

- Since it's intermittent when it pops proceed on that one.

- I think it's Sunroom run. On day two I would take feed off switch going to post.

- If pops then start excavating sunroom, if not, wait til warm weather and start diggin (literally) into post light circuit.
 
#39 ·
I am thinking that there is a nest of rodents that intermittently chew on the cables. Ask the HO how many times the breaker tripped in the past. Bet it was a lot.

I think the first breaker was worn out from being tripped too much.
That's what I would suspect also and we all know it can be almost impossible to pinpoint.
 
#38 ·
Split the circuit in half and see if the breaker holds. If it doesn't, work your way back from the middle of the circuit to the panel. If it does, work your way from the middle to the end of the circuit.

I'll bet it has something to do with the buried wire.
 
#41 ·
#42 ·
Had something similar a year back, no other previous electrician he had in could figure it out. I tried for about 20 minutes scratching my head and then ran out to my truck to grab my lan tracker as a last resort. I took off the last device and it tracked through. Then I switched the leads and found it stopped at the panel in the connector- bang it was a broken wire in the over tightened L-16. It would only short out at night as well when the cooler temperatures came.


480, check the connector- just as a suggestion. I chalk it up to luck finding it in my case but offer it as a suggestion.

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