I'm blessed with my old house. Someone had flipped it in 2012 and it has all recent appliances and a lovely 200A service box. Aside from finding a couple questionable electrical things (like some old knob and tube that was twisted together in a wall with electrical tape. I don't blame the electrician. It was in a wall and had nice clean cotton-jacket romex where it was visible, it just... umm - branched off to some K&T without a box somewhere in that wall to feed an obsolete box.
In the process of moving and adding a few outlets, I noticed that I have some phantom voltage. Part of this is likely due to a few older circuits not having a proper ground. For instance, all of the ceiling lights in two rooms are fed from one 12-2 line that doesn't have ground. I know that some phantom voltage is induced; 120v in a wire next to another wire makes fancy 60hz induction voltage.
A friend stopped over to help and double check my work. I know that adding an outlet is a no-brainer, but when you live in a box of 120-year old kindling, you kinda want to get it right.
He was a little concerned with the phantom voltage, and his suggestion was to separate the ground and neutral busses in the panel. Right now they're joined and both green/ground and neutrals meet side by side in a mix at the buss bar. I'm curious if that would work?
How much phantom voltage can I expect and how much is acceptable? Some circuits barely register, like .005v which could easily be multi meter error or induction. One circuit registered 13v which disappeared when I corrected a reversed polarity in the circuit. One measures 5.5V
I see problems with my stuff when there's anywhere down to say 3 volts. I've also had an electrician tell me and a customer that "that's normal". I think he just didn't want to fix it. I wouldn't worry about millivolts.
Whatever the topic, I usually have a clue of some sort about what I'm reading here.
Not this time.
imgon
HalfDork
9/6/20 12:49 p.m.
Where do you measure this voltage? Is that from the neutral wire to "ground"? Hot to ground with the circuit off? Could you have multiple reversed polarity receptacles?
If your panel has a main breaker the white and bare/green wires should be on a common bus. This bus should also be "bonded" (attached with a screw most likely) to the enclosure. If the main breaker is in a location other than that panel, the grounds (green/bare) should be on one bus and bonded to the panel enclosure. the neutrals should be on another bus that is isolated from the enclosure.
Whatever you do, don't level the living room floor.
imgon said:
Where do you measure this voltage? Is that from the neutral wire to "ground"? Hot to ground with the circuit off? Could you have multiple reversed polarity receptacles?
If your panel has a main breaker the white and bare/green wires should be on a common bus. This bus should also be "bonded" (attached with a screw most likely) to the enclosure. If the main breaker is in a location other than that panel, the grounds (green/bare) should be on one bus and bonded to the panel enclosure. the neutrals should be on another bus that is isolated from the enclosure.
The voltage potential is measured between line and neutral or line and ground (on circuits that have a ground). Breaker off.
The circuit in question is pretty simple and easy to trace. It goes across the basement up to a bedroom outlet. Then back down to the basement, over to under the bedroom/bathroom wall where it feeds both switches and an outlet in the bathroom. Then back down to the basement and across to the outlet(s) on the TV wall. All of it appears to be modern, yellow 12-2WG.
Main breaker is in the breaker panel. They are currently (pun intended) bonded with the screw. I'll snap a pic and be back. I'm pretty good with stuff from the breaker forward to appliances (load side), but all that big hefty stuff that comes into the panel from the pole is a little hazy for me.
Ok, here are pics. Typical Square D box. Obviously the two big insulated conductors are the two legs. Then there is the bare copper ground that leaves the bottom and heads outside to the ground peg, but what is the big mass of twisted aluminum strands go? The clamp that it's in is bussed to the ground lug as well.
imgon said:
Could you have multiple reversed polarity receptacles?
I'm pretty sure the one I found (the outlet for the dishwasher) was the only one. That was from the inspector when I bought the house. He said he checked every outlet, but I'm sure he didn't check light sockets (which, honestly, I don't care which way the electrons dance through a light bulb) During the 2012 reno, I noticed one of the light switches interrupted the neutral so I fixed that. Not that it's a big deal, but when the switch is off, I want the line dead, not the neutral.
What I was thinking of as phantom voltage is between the ground electrode at the meter and wait for it ... the ground itself. For example earlier this summer I was chosen (mainly because I know how not to electrocute myself) to go to a job. The drop to the house had about 9 inches of melted line. In showing the customer that it was an electrical problem I found 7 volts between the ground electrode and the ground itself. By ground I mean I stick my negative lead into the bare earth. Local electric company came out and found a squirrel donated it's body to science by electrocuting itself at the pole and it's body was still shorting it out. Checked electrode to ground and 0 volts. Everyone was happy. I've also seen electricians measure the two hots to ground and if there's a difference in voltage using that to trace it out.
Oh... no. This is breaker off, testing between line and neutral or line and ground. These were all tests at the outlet, not the panel.
imgon
HalfDork
9/7/20 5:29 p.m.
Sorry for slow reply. Sounds like your voltage is likely a shared neutral with another circuit and possibly more reversed polarity connections. Check ceiling boxes with more than one circuit. Split the neutrals into two groups. If you aren't having nuisance tripping on the circuit it likely won't cause more harm. Every time you work on a circuit in the future try to clean it up. Proper polarity, good grounds and you should eventually get the issue cleared. In the meantime always check like you are doing and avoid a shock. Happy hunting.
Curtis73 (Forum Supporter) said:
Ok, here are pics. Typical Square D box. Obviously the two big insulated conductors are the two legs. Then there is the bare copper ground that leaves the bottom and heads outside to the ground peg, but what is the big mass of twisted aluminum strands go? The clamp that it's in is bussed to the ground lug as well.
There are three wires coming from the pole: In your box they are the two big black ones and the bare aluminum one (neutral or, if I remember my terminology correctly, the "grounded" wire. Then there is the bare "grounding" wire that goes to your ground rod. The black ones are the hot ones, you get 120V from either one to neutral or 240V across the two black wires (that's how you get 240V for AC, hot water heater, stove etc).
The neutral and grounding conductor are supposed to be bonded together *only* at the service entrance (where it first comes into the building, which is usually but not necessarily the main panel). If there is no other box with a disconnect between the meter and your main panel, they should be bonded together. If you ever install a sub-panel fed from the main panel they should *not* be bonded there.
I've had one nuisance trip and it was on the circuit that I added a box to.
Here is the chain of events. 1) I moved a box about 1' to clear a fireplace installation. That was super simple because there was no drywall. The only thing I did was literally move the box to the next stud. 2) I added a second box by grabbing the unoccupied lugs of the outlet in the box I moved and wired up an outlet behind the framing of the fireplace because the fireplace has a circulating fan. 3) I pulled off the unoccupied lugs of the second outlet and took another (about 6') length straight up in the wall so I have an outlet for the TV which will hang above the fireplace. I simply left the pigtail hanging, but I stripped the jacket a few inches and put wire nuts on the line and neutral so I didn't bump into it and lose my hair. I finished that third step on Friday night. Saturday morning at 6 I woke up because the breaker tripped. Double checked the boxes and pulled the outlets out a little to verify that I hadn't pushed a lug against the ground. Retried the breaker and it tripped immediately each time.
That's when I called my electrician friend. While he was getting pants and coffee, I did a systematic test. I pulled every cord out of that circuit. I traced the entire conductor with a tone generator to make sure I had not missed a load on that circuit. Breaker still tripped. By the time my friend got here and verified that I had done pro work, the breaker was resetting and holding just fine. A complete puzzle. Once it was holding on its own, I systematically plugged things back in and wiggled wires, turned on loads, etc. All good. Two days later, the place hasn't burned down and the breaker is holding.
I know breakers can go bad, but they don't normally fix themselves in 20 minutes.
It was after step 3 that the trippage happened; 12 hours later. I should also add that this entire circuit is one of the few that was completely new during the 2012 reno. It is all 12-2WG from the panel to each box. No funky mix n match of wiring, just all recent romex.
