Strange Electrical Problem

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When one of our neighbors came back from vacation they found that the 20 amp single pole breaker for their hot tub and the 20 amp single pole breaker for their refrigerator in their detached garage had tripped. Neither GFCI type outlet served by these breakers had tripped.
The Garage circuit was about 12 years old and the hot tub circuit was only weeks old. The two breakers are not in close proximity to each other in the main panel.
They reset both breakers and they have not tripped since [two weeks].
Today the sixty amp double pole breaker that is feeding a recently built master bedroom / bathroom tripped. This breaker feeds from the main panel to a subpanel that houses the breakers for the addition.
The subpanel includes two 20 amp single pole Arc-Fault breakers for the bedroom, two twenty amp single pole breakers that feed directly to two GFCI type outlets in the bathroom and two unassigned breakers.
At the time the 60 amp breaker tripped only the two Arc-Fault breakers were turned on. Neither of the Arc-Fault breakers tripped. Therefore it seems unlikely that an event from the new room caused the 60 amp breaker to trip.
At the time of the trip, the total load on the 60 amp breaker, via the new addition subpanel, was comprised of one digital one analog alarm clock.
Prior to and after the 60 amp breaker tripped the branch circuits served by the new addition subpanel were tested with an Ideal #61-155 circuit analyzer.
This device tests for a host of electrical problems, including: True RMS, voltage drop, line voltage, peak voltage, frequency, ground impedance, hot and neutral impedance, ground-neutral voltage, false and false grounds. Everything tested perfectly.
It also successfully tested the GFCI outlet devices and the Arc- Fault breakers.
This test runs the entire circuit, including the conductors used between the main panel and the new subpanel and the new 60 amp double pole breaker in the main panel that supplies the new subpanel.
Assuming that any trouble in the new addition would have tripped the Arc-Fault breakers, we guessed that the problem must lie somewhere between the new subpanel and the existing main panel. This would reduce the scope of the search to the conductor, the new 60 amp double pole breaker and the main panel.
The conductor is brand new copper UF cable. The Ideal meter test showed no indication of high impedance. An inspection of the main panel showed no indication of a short circuit, arcing or overheating.
When the 60 amp double pole breaker was turned back on it stayed on and was cold to the touch. When checked thirty minutes later with an infrared thermometer, the temperature was normal, as were the rest of the breakers.
It should be noted that the 60 amp circuit that supplies power to the subpanel for the room addition had been turned on over six weeks ago and had operated flawlessly until this afternoon.
Any one of the single pole breakers tripping would just be an anomaly that would not need to be answered unless the problem recurred. But the 60 amp double pole breaker tripping under no load has caused my friends some concern.
Can anyone think of a circumstance that would cause the problems that they experienced?
TIA
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I know exactly why, somethings fucked up and they need to get the contractor back out there before the house burns down.
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wrote:

Thanks for the insightful review of the problem, Al. The contractor and the electrician have both been to the job and both are baffled. The electrician spent hours testing the system with everything testing perfectly.
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Just a couple of real WAGs.
Surges on the supply line? Vermin crawling through the breaker box? A prankster in the house?
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Were the handles of the breakers found in the "tripped" position or the "off" position, and what brand circuit breaker?

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In many breakers like Cutler-Hammer, they trip all the way to the off position.

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This is a GE main panel.

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On Tue, 31 Jan 2006 07:03:28 -0500, "RBM" <rbm2(remove

They were tripped, not just simply turned off.

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IF all the tests and visual inspections were done competently, then my first course of action would be to replace the breakers. Cheap or defective breakers trip easily. Power fluctuation from the utility are common, and if a breaker can't take a normal fluctuation without tripping it is a nuisance. My other concern would be the fridge. It seems to be the likely suspect here (assuming the wiring tests out OK). If the capacitor in the fridge is on it's way out it would cause intermittent surges. You might get it tested. Many a fire has been started by a failing fridge.
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change breakers that tripped with brand new ones. if another trip occurs on the fridge circuit move it to another location. if fridge trips breaker at new location then you know its the cause.
intermittent troubles can be a pia
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BP wrote:

how would you know it was a normal fluctuation; could have been a one in 20 year fluctuation.
"Many a fire has been started......." Like how many? Out of every 100,000 home fires, how many started by a failing refrigerator? In fact, how many started by any failing large appliance propertly installed, including clothes dryers which do start fires?
After the OP's test the obvious course of action is to be watchful but do nothing.
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So many shots. So little time.
An apartment building in my town burned to the ground last year, started by a fridge. Old compressors overheat....lots of dust.... There is a great little gadget on the web called Google. You should try it. Just type in "Refrigerator fire" and see what you get.
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Ajax wrote:

My first thought is to wonder if they pulled those breakers out of some condemed house, and they are used and warn.
My second thought is somebody is pulling your leg. Though tripping a 60A breaker would take a bit of courage.
My third thought is that I need more coffee.
--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
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... : : It should be noted that the 60 amp circuit that supplies power to the : subpanel for the room addition had been turned on over six weeks ago : and had operated flawlessly until this afternoon. : : Any one of the single pole breakers tripping would just be an anomaly : that would not need to be answered unless the problem recurred. But : the 60 amp double pole breaker tripping under no load has caused my : friends some concern. : : Can anyone think of a circumstance that would cause the problems that : they experienced? : : TIA
All the "testers" in the world, great as they are most of the time, are only as good as their design and the users.
I'd say it's time to put the testers away and get down to some real world troubleshooting with eyeballs and good old analog meters after eyeballing what's about to be measured. I just got thru with a 4-trip "fix" for a battery discharging problem in my Buick. They pronounced it fixed each time I picked the car up. It wasn't, and it took me all of about 5 minutes to get out my Triplett, disconnect the positive terminal of the battery, and see in excess of 3 Amps flowing with everything turned off and the doors closed. But it tested perfectly every time on their "tester". It's $650 later right now, it's fixed finally, and I'm waiting for them to respond to see if I take them to small claims court or they drop the phoney fixes that weren't fixes, thanks to their computer diagnostics et al.
I have no idea what your source of the problem may be though. Can't see it, and wondering if the testers are doing what they need to do in this particular case.
HTH,
Pop
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Sounds to me that they have to go over the innards of the main, and the feed line to the subpanel inch by inch. Wearing eye protection and gloves, wiggle the cable on every staple and box clamp. Check for wire exposure on the inside of every box, gaps in tape covering of splice connectors etc.
It could be a piece of defective cable, or an over tightened box clamp that only causes a short when the cable moves (thru temperature changes, wind shake or whatever).
I have encountered defective cable where it's not possible to see the defect, even after it's blown the breaker multiple times. In my case, it was a solid short. In this case it sounds like an externally-induced intermittent.
An intermittent short of this nature won't be detectable with any kind of metering until its fried the insulation enough to provide a carbonized conduction path. You don't want to let it go that far...
Either that, or they have gremlins.
Run the thermal detector over the inside of the main panel and subpanel too.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Chris Lewis wrote:

That thought just occured to me as well. Breakers are not electronic but thermal in nature. If that room of the house became very hot for whatever reason, you could get a lot of trips from odd circuits.
Also check for water or other conductive fluid leaks in the area of the panel.
--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
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On Tue, 31 Jan 2006 16:22:05 -0000, snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

Chris, I think that you were very close to what we discovered was the problem. After replacing the 60 amp double pole breaker with another new breaker, it continued to trip. Thinking that one of the Arc-Fault breakers in the subpanel could somehow be at fault, all breakers were removed from that panel and the 60 amp breaker continued to trip after about ten minutes.
When the conductors were removed from the 60 amp breaker, it didn't trip. A test of the resistance in the conductors (underground UF cable) were within normal ranges.
Next step: excavate the UF cable.
Problem: One of the homeowners buddies who had helped him install a PVC line for a sewage pump had nicked the UF cable with a saw while cutting the existing PVC line. He just drove the saw into the ground as he cut the pipe, even though he had been warned that there were electric lines in that area.
The cut in the insulation was enough to cause some arcing between one of the hot legs and ground. We suspect that the recent we weather enhanced the ability of the conductors to arc. Part of the mystery is that he did this work last Wednesday and it took until the following Tuesday to start tripping the 60 amp breaker. A few splice connectors with heat shrink insulation and the circuit is purring like a kitten.
Lesson: Never trust a plumber with anything sharper than a can of PVC glue.
In retrospect, what is really strange is that the saw cut never tripped the breaker and he nicked both a hot leg and ground. I looked at his saw and there was no sign of arcing that is so indicative of a metal object hitting a live cable.
Anyhow, thanks to everyone for their input.
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electrical lines? The fact that the lines were installed that close makes my head hurt. Anyway, thanks for posting the solution. It isn't often we get to see that in these groups. And we can all use the knowledge!
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He never turned the power off - that we know for certain. It was a point where the sewage pump line intersected the 60 amp circuits conductors.
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Ajax wrote:

well the saw blade would have been spinning so fast you wouldnt see the arching. Anyway, If he hit the 220 I'm surprised he didnt feel it. Maybe he was high, lol.
Im surprised 220 will jump like that. There is the possibility that the voltage was so lowered by the cut that the appliances on the other end pulled more current to satisfy their needs. But that should have tripped the sub-panel too.
The arching was between a leg and ground, or between a hot leg and the neutral? This was a 3-wire or 4-wire 220 setup?
Nice to know you found and fixed it. It was an entertaining puzzle.
--
Thank you,



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