100 year old house wired with AC/BX. Seems to be BX wired all the way back to the (current) breaker box. At the electric box, if the circuit is energized, the metal box is hot, but the armored cable at the breaker box is at ground. Almost has to be a break in the BX shielding, right? The GFCI outlet in the box works.
Hot electrical box
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Jadnashua
Retired Defense Industry Engineer xxx
At the panel, ground and neutral are tied together. Ground should never be used as a current conductor when things are working properly. It may be a problem that is using the ground as a conductor that's warming things up. Depending on the length and soundness of the system, there is often at least some resistance between the ground and neutral. Old BX insulation can get hard and crumble if you move things, creating a loose or hard connection where you might not expect it. The metal sheath may look fine and be fine, but over time, it, too can corrode making problems.
While it can be confusing, even though neutral is connected to ground at the panel, any circuit needs two wires to allow for a complete path for the current and one of them shouldn't be ground. IOW, there's current on the neutral wire when you're drawing power even though it's connected to ground elsewhere.
While it can be confusing, even though neutral is connected to ground at the panel, any circuit needs two wires to allow for a complete path for the current and one of them shouldn't be ground. IOW, there's current on the neutral wire when you're drawing power even though it's connected to ground elsewhere.
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Thank you for the response. Don't know if I was descriptive enough in initial posting. At the outlet box in the wall the metal box tests 118v to the neutral wire. In other words, both the hot wire (black) and the box itself are at 120v to neutral. Somehow, the metal sheath has to be making contact with the hot wire, but not grounding out. Third floor of the house - definitely not easy to run a new circuit
John Gayewski
In the Trades
Is the box nailed to a stud in the wall?
Jadnashua
Retired Defense Industry Engineer xxx
FWIW, a metal box is supposed to be bonded to the ground lead, so if that were true, it would have tripped the breaker before this. Most switches and receptacles you'd screw in will also ground the box, assuming they're fairly new as they'll have a ground lug on them (older ones often do not).
If I had to guess, the most likely location for the problem is at the clamp for the wire going into the box. Hassle is, the clamp may not be accessible once the wallboard is installed.
You might have to cut the nails off, slide the box out to have access to the cable going in...locate the nicked insulation and since you can't nail a new box in, probably put a new one in with either the clips, or a plastic box with the wings that clamp it into position.
If I had to guess, the most likely location for the problem is at the clamp for the wire going into the box. Hassle is, the clamp may not be accessible once the wallboard is installed.
You might have to cut the nails off, slide the box out to have access to the cable going in...locate the nicked insulation and since you can't nail a new box in, probably put a new one in with either the clips, or a plastic box with the wings that clamp it into position.
WorthFlorida
Clinical Trail 5th session completed 4/24/24.
How old and the type and brand is the panel?
It it a sub panel?
Single phase or two phase (220v)?
If the box is hot it should be tripping a breaker. Shut off all of the breakers and check if the box is hot? If it is check the power feed and shut off the main. If not hot then turn breaker on one at a time checking voltages. First time around switch on one breaker, check voltage then shut off the breaker and go to the next one.
It it a sub panel?
Single phase or two phase (220v)?
If the box is hot it should be tripping a breaker. Shut off all of the breakers and check if the box is hot? If it is check the power feed and shut off the main. If not hot then turn breaker on one at a time checking voltages. First time around switch on one breaker, check voltage then shut off the breaker and go to the next one.
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Eaton main panel (200 A), Cutler Hammer sub-panel (100 A), 100 A feed from the main. Not sure how old either the main or sub panels are, but definitely re-wired. Old main would have been fuses. Wall box is hot unless you turn off the breaker for that circuit or the feed in the main panel.
John Gayewski
In the Trades
My suggestion would be the same as above. Turn off. Remove box. Inspect.
Install new cut in box and fix the wire. You may need some drywall mud by the time you get done.
Install new cut in box and fix the wire. You may need some drywall mud by the time you get done.
Fitter30
Well-Known Member
Would inspect the wires in the junction box very close. With cloth and rubber for wire covering doesn't take much. If you can gently straighten the wire and take striped wire insulation and slide it over existing wire and a piece of heat shrink tubing. Worked on a building built 1929 had the same wiring till it got rehabed 25 years ago.
I would first determine if this is a high impedance connection to hot power, or a short circuit.
This is not to say that I would ignore a high impedance connection, but I would want to characterized it before searching or disturbing things. I would not want to "fix" it just because I was poking around and the symptom disappeared.
This is not to say that I would ignore a high impedance connection, but I would want to characterized it before searching or disturbing things. I would not want to "fix" it just because I was poking around and the symptom disappeared.
WorthFlorida
Clinical Trail 5th session completed 4/24/24.
Reach might be onto something. A subpanel (where it seems to be hot) the ground and neutral are not common (not connected), only at the main panel. Current returns to the main panel on the neutral. The ground is for safety. If the neutral back to the main has a poor connection, (high impedance) measuring between the neutral and ground will show voltage.
With a GCFI tester, does pushing the test button trip the GFCI? If yes the ground (green wire) is connected, if no, there is no ground, only neutral.
When a GFCI tester is plugged into this outlet box that is hot, does it all check good?
With a GCFI tester, does pushing the test button trip the GFCI? If yes the ground (green wire) is connected, if no, there is no ground, only neutral.
Kreemoweet
In the Trades
So I take it there is no grounding other than the armored cable sheathing?
If the ground path back to the service neutral is interrupted/very high resistance, then
it could very well be that the box (& cable connected to it) could register as hot
with a multimeter or no-contact voltage sensor, due to capacitive/inductive coupling.
It's called "phantom voltage" and is harmless. You could test this by taking a small 120V bulb holder
with two wire leads, and touching one wire to the box, and the other to the neutral. Usually,
the bulb will not light up. If it does, you've got a real problem.
If the ground path back to the service neutral is interrupted/very high resistance, then
it could very well be that the box (& cable connected to it) could register as hot
with a multimeter or no-contact voltage sensor, due to capacitive/inductive coupling.
It's called "phantom voltage" and is harmless. You could test this by taking a small 120V bulb holder
with two wire leads, and touching one wire to the box, and the other to the neutral. Usually,
the bulb will not light up. If it does, you've got a real problem.
No ground other than the AC sheathing. I found this situation when I plugged in a trouble light with a metal cover and went to hang it up on the shower. Zap! Tripped the breaker for the circuit. Not phantom voltage. Will have to remove the box and, unfortunately others connected by the sheathing in the circuit and try to find the short. Once again, not easy to run a new circuit, being on the third floor, but may be necessary.
Thanks for everyones' help
Thanks for everyones' help
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