Trouble-Shooting Residential Electrical System

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dantran

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Omaha, NE, United States
I've got some peculiar behavior from a residential system. Some Hots (terminals of load breakers) and Neutral test continuous with continuity test in panel. However, when breakers (main and load) are closed in, system faults do not clear - with the exception of one breaker that is permanently in 'open' position. When I try to close this breaker, it immediately opens/faults.

The other peculiarity is that one circuit in the kitchen (for above counter receptacles) tests normal at ~118.5VAC when breaker is closed in, however it tests/hovers at ~12-14VAC when breaker is open. I haven't found/confirmed this behavior with any other circuits other than this one but will be looking for it.

This is an older Federal Pacific load center. I'm fully aware there are divergent and some strong opinions on safety issues related to this manufacturer. I'd like to keep this focused on trouble-shooting what's going on if possible. AHJ has indicated he is not requiring service/load center upgrade and I'm working within customers' constraints best I can.

Suggested trouble-shooting methodology? I've got my step by step to figure out what's going on but would appreciate people helping think through best method to find fault/issue and then I'll post my thoughts. My theory is that there's a high resistance fault somewhere in the system that is drawing some current, but not enough to trip breakers. Perhaps related to the breaker that is permanently open... I haven't taken an ammeter to anything in steady state yet but that may be telling as well.

Grounding electrode system not currently bonded to panel because of some work of a plumber - and this will be done soon, but I'm not sure this would explain the behavior above.
 
dantran said:
The other peculiarity is that one circuit in the kitchen (for above counter receptacles) tests normal at ~118.5VAC when breaker is closed in, however it tests/hovers at ~12-14VAC when breaker is open. I haven't found/confirmed this behavior with any other circuits other than this one but will be looking for it.
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This is probably just an induced voltage from another wire that is laying parallel to the one under test. There is probably very little amperage which you could verify by putting a 12 volt load on it. (An auto lamp perhaps. It won't light.)

dantran said:
This is an older Federal Pacific load center.
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Good luck. :eek:
 
dantran said:
I've got some peculiar behavior from a residential system. Some Hots (terminals of load breakers) and Neutral test continuous with continuity test in panel. However, when breakers (main and load) are closed in, system faults do not clear - with the exception of one breaker that is permanently in 'open' position. When I try to close this breaker, it immediately opens/faults.
Click to expand...

Regarding this portion of what you wrote. And I apologize up front if this is assuming something too simplistic. Your wording has me wanting clarification. If I understand, you are saying that with the breakers in the off position, you read "continuity" between the hot and the neutral. You are wondering why the breakers don't trip as in you believe you are reading a direct short. Is this correct?

If my above is accurate, then you may not be reading "continuity". Many testers today don't have the sensitivity to measure minute resistance, and motors, for example don't have significant resistance, more specifically their load characteristic is impedance. A simple way for you to tell is use a clamp on amp probe on those circuits. If it is less than the breaker rating then this is likely an AC impedance load as opposed to a resistive load.
 
K8MHZ said:
I would start with this. You either have a short circuit or a bad breaker. I am leaning toward short circuit. So, to start, I would test for those and after that make further plans.
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+1.

if you can, disconnect all the loads on the circuit first and see if it still trips. If so, it is likely a short in the wiring or a failed breaker. if not, it is probably a short in a utilization device.

In any case, it is probably best to replace the breaker since repeatedly opening on short circuits may damage them.
 
Welcome to the forum!

If there is any load on that circuit, e.g., a plugged in clock, a light bulb, heat trace, etc., it will show continuity and not voltage.

The 12-14VAC may be induced voltage or a partial failure in the breaker. I'd test from that point to another ungrounded conductor on a different circuit with no loads on it and the breakers on. If both of those circuits are on the same leg in the panel, you should have continuity between them. If they are on different legs, you should have 240V between them. I'd also test hot to neutral, hot to ground, and neutral to ground.

The breaker that flips back (trips) immediately may be bad, especially if there is no spark or pop. I had a CH CH breaker fail like that on me a few months ago. Remove it from the buss, unland the wire, and reset it unpowered; if it "trips" in your hand, the breaker is the culprit. If not, there is a short in the wiring of that circuit.

Most FPE Stab-Lock breakers fail to trip, not nuisance trip. Given their very high failure rate of not tripping a second or next time, I'd replace tripped breakers. I think UBI makes FPE replacements that are available at HD.
 
ptonsparky said:
Neutrals and hots should have continuity. It's called the "load". Disconnect every appliance, fixture, dimmer and GFCI, then check again. Some dimmers used an EG for their electronics.
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+1

You may have to open up several boxes/openings to determine where the problem is. Disconnect the hot and neutral both from the panel to reduce possible nuisance readings.
 
The problem with the one breaker failing to reset is probably caused by the black (line) wire miss-connected to another circuit. The usual place for this to occur is where a switched receptacle switch is located in a switch J box which has another switch in it from a different circuit which is located on the other leg causing a 240 volt potential. Sometimes someone gets into the J box and mixes the wiring. When the switch is thrown it instantly shuts off. When this same thing happens where both are located on the same leg the CB does not trip and you will find that you cannot shut off the power to it until you have both CB's off.

The resolution to this is turning off all CB's, then turning on the one which will not reset. If it sets you have identified the problem. To find the one it is hooked up with turn on the other breakers one at a time until one will not reset or trips. Either breaker may trip, but usually the first one you had a problem with. Once the two circuits and two CB's are confirmed check all switches connected on those circuits.

The other problem was more or less dealt with, as another poster said it is probably ghost or non existent voltage. Many modern multitesters will give you this false reading. Use an old style solenoid wiggy to check for power. Ghost voltage will not show up on that. Or you can use one of the multimeters which have a low Z setting to check such as Klein's.

Good luck with it.
 
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How many problems do you have???

How many problems do you have???

dantran said:
I've got some peculiar behavior from a residential system. Some Hots (terminals of load breakers) and Neutral test continuous with continuity test in panel. However, when breakers (main and load) are closed in, system faults do not clear - with the exception of one breaker that is permanently in 'open' position. When I try to close this breaker, it immediately opens/faults.

Start with ALL breakers off, and close one at a time. See if problems are on Both legs or just one.

The other peculiarity is that one circuit in the kitchen (for above counter receptacles) tests normal at ~118.5VAC when breaker is closed in, however it tests/hovers at ~12-14VAC when breaker is open. I haven't found/confirmed this behavior with any other circuits other than this one but will be looking for it.

Use a wiggy type tester.


This is an older Federal Pacific load center. I'm fully aware there are divergent and some strong opinions on safety issues related to this manufacturer. I'd like to keep this focused on trouble-shooting what's going on if possible. AHJ has indicated he is not requiring service/load center upgrade and I'm working within customers' constraints best I can.

Suggested trouble-shooting methodology? I've got my step by step to figure out what's going on but would appreciate people helping think through best method to find fault/issue and then I'll post my thoughts. My theory is that there's a high resistance fault somewhere in the system that is drawing some current, but not enough to trip breakers. Perhaps related to the breaker that is permanently open... I haven't taken an ammeter to anything in steady state yet but that may be telling as well.

Forget this breaker and leave off till you know you have a working system

Grounding electrode system not currently bonded to panel because of some work of a plumber - and this will be done soon, but I'm not sure this would explain the behavior above.

Run a jumper around his work and make a good ground. If it is a neutral problem there is no backup path.
Click to expand...

Good luck use a wiggy tester so it puts a load on circuit.
 
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