I ran across an unusual electrical goof today while replacing a 200Amp panel with a new one. The goof leads me to question what would, or should, and is, happening.
Here is the situation:
I unhooked a breaker, hot wire first as I always make a practice of doing. I then unhooked the neutral (Grounded wire for you tech nuts) and the ground wire. They each were in their own screw on the block. As I removed the ground wire a small arc developed. After a few seconds of puzzlement I decided to put the wire off to the side to troubleshoot. As I did so I touched the copper of the neutral and got a little extra energy inputted into me. As if I was still in disbelief I touched the neutral and ground together and got arcing.
I reasoned the DIYer ahead of me (this is how I got the job, he got too overwhelmed) when he spliced into the old rayon wiring in the house wasn’t too careful at what he was doing and somehow he junctioned into two circuits instead of one. The reason I know this is because after tracing it to two junction boxes and seeing the terrible rats nest of electrical tape taping wires all together and overloaded boxes where he spliced into the rayon wiring, I actually gave up troubleshooting it, put it off til tomorrow, too big a mess.
I located the other breaker that was “looping” power, or otherwise energizing the neutral, shut it off and that was that. I figure it out tomorrow. BUt…it gives rise to the question, he obviously has it wrong, he obviously had a secondary breaker that was energizing the neutral, and yet the neutral was in the neutral bar on the panel. Does this mean that technically the panel cabinet was energized but no shock was felt touching the panel because the current was traveling to the ground rod into the ground? Other than a shock hazard, is there some other danger from this goof?
Replies
I will have to reread this tomorrow and see if I still see it this way, it's late and I'm tired, but at first blush it sounds like you have a shared neutral and possibly something faulted and feeding current down the ground wire.
It is unclear if the breaker your working is the main, a main in a sub panel or a breaker on a branch circuit. It is also unclear if your lifting the incoming or outgoing neutral and ground. I kind of assume it is a branch breaker and your lifting the neutral and ground serving that circuit.
I plan on coming back at it tomorrow evening. In the mean time you get a WAG and a bump. Almost exactly but not completely unlike a bump and grind.
Sounds right. Shared neutral = inbalanced load. Just enough to get the arcing and mini zap. getting a hot wire tied to a nuetral in a J box some where would have given him a dead short.
Dave
Dead short?
You mean I'm getting a short circuit but it is somehow canceling itself out due to some bizarre way it was wired?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I read this somewhat differently.First forgetting the neutral lets look at the ground wire.It is the one that was arcing. That means that it was carrying current.Now, by current code, all grounds in a box should be joined. Even if from different circuits. Also code allows for non-grounded receptacles to be grounded by running a separate ground wire to panel ground or junction box that gets back to the panel ground. Of course with this kind of wiring problems no one knows. I have no idea of what kind of loads you might have. But anything, specially equipment with a motor, might have an insulation breakdown and put leakage current on the ground wire. It might be a few ma or a few amps. If you have an amp meter that is the best monitor the current in that ground and turn off ALL of the branch breakers. Then turn them on one by one and monitor which one(s) cause the current in the ground. Another possibility is that you have a light or similar connected hot to ground.
Yes these were branch circuits inside a main panel. I could see it being a shared neutral because the neutral wire is part of a 12/3 cable and the breaker I shut off happened to be the third wire in that cable. So I'm wondering if it is as you suggest, a fault somwhere.
Interesting how the fault didn't trigger a breaker trip or anything. When I metered it I got a full 120V on the neutral. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Maybe I'm not understanding this, and I'm not a pro, but I think maybe nothing at all is wrong. A different breaker was supplying voltage to the other hot conductor of a 3 wire circuit. Let's assume it was connected to a lighting circuit which was switched on. When you lifted the neutral, you broke the circuit, got a little arc, the lights went out. With no complete circuit, there is no voltage drop across the load, and the neutral is of course reading 120 volts wrt ground. So when you touch it to ground, you complete the circuit, get a little arc again, and the lights go back on.
OK, just reread your original post, and I see you also mentioned arcing on the ground wire (but you didn't mention metering 120 volts on it or not, as you did on the neutral). So you might also check for a 'bootleg' ground somewhere (neutral jumpered to the ground), which you definitely want no part of.
Edited 11/23/2005 10:39 am ET by r
Perhaps I should clarify some more just to be sure all read this the same way.
I metered the neutral and ground wire (one lead of the meter on each conductor) and read 120 volts. The wire was completely unhooked from the panel dangling out overhead outside the panel.
Today when I went back to try and figure out the problem here is what I did. I hooked up the red and black wires of the 12/3 cable to a tandem breaker. I connected the white wire to the neutral bar in the panel as well as the ground wire to the bar I was using as the ground wire bar. I then took the OTHER branch circuit, which was a 12/2 wire which was the wire that juiced me yesterday and completely unhooked it from the panel so that all 3 wires of the 12/2 branch were unconnected. I then flipped on the breakers on the tandem to energize all of my 12/3 circuit wire I just hooked up. Then I metered the OTHER branch circuit (the 12/2 wire), the one I totally unhooked in the panel. I metered the neutral and ground wire together and read 120v. This tells me that the 12/3 cable is energized of course, and that SOMEwhere downstream the 12/3 wire must meet up with the 12/2 wire. . I found that somewhere and looked at it, it's a rats nest from hell. I dunno what the guy before me did, but it's sloppy, hard to troubleshoot, and obviuosly has to be wrong for me to get 120v on a neutral. Somehow, one of the hot conductors of the 12/3 cable is energizing the 12/2. Manwhile the 12/2 black wire was connected to its own breaker.
I was wondering since the 12/2 black wire was wired up to a breaker turned on, and its corresponding neutral was energized and dumping current to the neutral bar, what kinds of problems that presents. To me that means the panel is energized but I doin't get shocked for some reason. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I may indeed be wrong but this still sounds like a shared neutral.
Bottom line is you should get and electrican and stop messing around in the box. A white wire will kill you just as dead as a black one. Electricity wants to do one thing, flow in the course of least resistance, whether it be a copper wire or a human body... it doesn't care.
Sledge, this is something new to me, I don't know everything. I replaced quite a number of panels before and never encountered a situation where when I touched a neutral wire I got a jolt. Thus the question, as I WANT to learn from this so next time I'll be prepared.
I don't claim to understand electrical theory. It has always amazed me how I can touch the neutral bus in a panel and not get shocked when clearly there are loads using current on the branch circuits. As I understand basic electricity, current flows in a loop, from Hot to ground (neutral wire in this case) meaning therefore that there IS current coming back to the panel to the neutral bus. Why the hot shocks you and the neutral doesn't, I never could understand that explanation, I just know that's the way it is.
So you can imagine my surprise when a neutral from the 12/2 wire zapped me and the current was coming from a separate 12/3 cable. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
quick explanation of you getting shocked when you touch the HOT (other than the obvious - it's HOT/energized) is you become the neutral (or ground - aka path of least resistance)
other point of interest - electricity can "backfeed" to make a hot out of a neutral/ground,
Here is some easy electric theory. Take the black wire from a breaker and attach it to the brass screw of a porcelain fixture. Stub a white wire from the silver screw of the fixture and the neutral bar in the panel. screw in a 150 watt bulb, grab both the white wires, throw the breaker and report back your findings.
Actually don't try this cause it'll probably kill you.
From your postings I would reccommend you learn alittle more about electric theory before venturing into the panel box again.
Call an electrician they are cheap compared to emergency room doctors.
"I was wondering since the 12/2 black wire was wired up to a breaker turned on, and its corresponding neutral was energized and dumping current to the neutral bar, what kinds of problems that presents. To me that means the panel is energized but I doin't get shocked for some reason."Define ENERGIZED?"I metered the neutral and ground wire (one lead of the meter on each conductor) and read 120 volts. The wire was completely unhooked from the panel dangling out overhead outside the panel."Meaningless, you could have a completely correctly wired circuit and see that.First of all electricity only has meaning when measured between the two terminals on the generator or transformer or battery. It is not untill it is connected as a SYSTEM that one terminal is grounded and can be used as a reference.HV transission lines ( 0ver 100kv) are sometimes worked on "hot". A basket is suspended from a helicopter. The first thing that is done is that the basket is "grounded" to the hot line. While the basket and the hot wire is over 100 kv referenced to ground or the metal tower the worker in the basket does not see any difference between himself and the wire.Now you measured 120 volts between a disconnected ground and disconnected neutral wire, while the hot was connected.Now measuring between the panel ground bus and the neutral and the ground bus and the circuit ground wire would have given us some more clues.Also it is not clear if this is a service entrance, where the neutral bus is bonded to the grounding electrode system or not. If it is not you might have other problems in the feed wires.If you have a "load" on that circuit then this is to be expected. The load does not need to be much, it can be a door bell transformer or night light. And if the equipment grounding conductor is connected to other equipment grounding conductors, per code, then you can measure a full 120 "disconnected" ground to disconnected neutral.There could be many other strange things going on. From example there might be a 2 door bell or HVAC transformers whose outputs got parralled, but driven by separate circuits. That could give you an ISOLATED 120 volts into the 2nd circuit.
This wouldn't possibly involve a 3 way switch, would it? My parents had a garage built and a friend of theirs wired it (he was an electrical engineer, complete with blue and white striped cap). The lawn service guys kept saying they got shocked when they would touch the garage siding (aluminum) and the mower at the same time. I checked it with a meter and test light a few times and could never find a problem. I did, however, feel a pretty good tingle in my bare feet when I went out to the garage to close the aluminum jalousie windows one night. When we were selling the house, I went around and checked all of the outlets to see if there were any issues that could affect the sale and found that the hot and neutral were reversed on the outlet in question, but went back to normal when one switch was flipped. Turns out that the EE (with the cap) was switching the neutral in the 3 way circuit. Since I couldn't think of a reason to flip the switch from the garage, I removed it and replaced the 3 way in the house with a normal switch. Problem solved.
"I cut this piece four times and it's still too short."
"Other than a shock hazard, is there some other danger from this goof?"
WW,
Isn't that THE hazzard.
WSJ
Willie: Either the neutral was spliced to another circuit or you didn't shut the right breaker off. Any load on a circuit will, no matter how small even a clock or a night light, will feed though 120v. There would not be much in the way of amperage available but the voltage would be full circuit voltage. If there was no load whatsoever the neutral would be at ground potential. Draw it out on paper, you'll see what I am talking about.
Duke the Electrician (30 years in 5 retired)
The Bill of Rights
December 15 1791
NRA Endowment Member
LEAA Life Member
CRPA Member
ww,
One thing that has not been mentioned is the possibility of a properly wired circuit with two hot lines and a shared neutral. Only problem could be that the two breakers feeding the circuits are, by code, supposed to be tied together so if you turn off or trip one of them, the other is also supposed to turn off. This is to avoid the exact problem you are having. The attached digram shows such a circuit, even though it is describing a AFCI breaker, the circuit is the same. If you notice, the breaker is a double pole type, so that if one side trips, the other side is automatically dead too. Same with turning it off, you cannot only turn off one circuit using the neutral, you have to turn off both.
Hope this helps,
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
The basis of this thread is a mater of surprise being bit by a neutral wire, and not understanding why. Look at any switch bank inside a front entrance. There may be 5 or more switches all wired to different circuits sharing the same neutral. Bottom line is... anyone that thinks a neutral is harmless does not belong in a circuit panel box.
I could really bend your mind with how to burn down a house by shorting out those cheap 12v outdoor lights... but this is obviously electric 101 and alot of the class is failing.
Perhaps the easiest way to describe the cause of WW's shock is that when he disconnected the common from the bus bar, he broke the "loop", and when he got the shock, he completed the loop again through errant fingers or some such thing. I'd have to agree with sledgehammer, that if one can't get their head around the concept of being shocked by a common wire, then they don't belong in a service panel or junction box. The way to learn this one is through theory, not trial and error.John
I'd have to agree with sledgehammer, that if one can't get their head around the concept of being shocked by a common wire, then they don't belong in a service panel or junction box'
I already explained that I know I'll get a jolt if I touch a neutral wire that is disconnected from the panel and there is a load on the line. Duh, yes, I then become the conductor the returning electricity goes thru.
But I should NOT get a jolt on a neutral wire belonging to the breaker I just shut off that belonged to that 12/2 cable, now should I? Unless someone miswired elsewhere and crossed circuits? I don't dispute that is what happened, it has to be what happened. I was merely wondering what the resulting impact would be by feeding a direct 120v to the neutral bus of a panel.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Yes, you're quite correct that the common wire from a 2 wire circuit should not shock you if the corresponding breaker is off. In the case you've described with the wiring error further along, you'll only see the 120 v on the common when you disconnect it from the neutral bus. Feeding this direct 120 v into the neutral bus is merely completing the circuit as it normally functions and allowing current to flow. The confusing part is that you thought (reasonably) that you'd shut off the breaker, but the sloppy wiring you described in the jbox effectively meant that you hadn't turned it off. So the end result you see between the common wire and the neutral bus is the same as what you'd see if you hadn't shut off any of the breakers.So in trying to answer the first question, what would happen is the circuit would function properly (assuming the rats nests in the jboxes were not causing additional mysteries). Personally, I'm very reluctant to work on a hot panel, and usually turn off the mains if its at all practical before making changes. Nothing much worse than fixing the sloppy guys mistakes is there? Glad you got the fault figured out in any case.John
Here is an interesting example that show how multiple problems can give you strange electrical problems.Trouble shooting is not too hard as long as it is a "simple" problem. But have compound problems and you need to understand EVERYTHING that is going on.This is from a email from E&M magizne." Nightmare Installations
Wishy-Washy Installation
After completing the wiring for a clothes dryer and plugging the cord into the receptacle, I placed one hand on the dryer and one on the washer to climb out from behind the unit. In doing so, I received a terrible shock. I pulled out my meter and measured 120V between appliances. I knew the washer was bonded to the copper water line so I double-checked my wiring. My work looked good. Additional measurements showed 120V receptacles measuring 120V (white wire) and 240V (black wire) to remote earth.Although it was a rainy night, I wanted to check the outdoor service entrance (SE) panel. A shock from the SE panel convinced me it could wait. Morning light revealed no ground rod at the SE panel. The triplex SE cable was terminated correctly on the pole-mounted transformer, and the transformer tank was bonded to the pole ground. However, there was no ground strap from the transformer neutral bushing to the tank.A lack of ground at either end of the SE triplex created a floating neutral. Also, one transformer secondary line bushing was cracked. I reasoned that during wet weather the cracked bushing would short to the transformer tank establishing a ground. The floating neutral went to 120V, and the other side went to 240V. Replacement of the transformer and installation of a ground rod solved the problem.Terry Johnson
Iowa City, Iowa "
think you and Jdowney got the point across better than most - be interesting to see if WW "listens" - otherwise - job securityBTW - I'm guessing the 12v as an ignition source involves the transformer and/or extension cords(?)
I guess you're not understanding some of what I"m saying and that's ok, I did my best to explain it, what can I say, I'm always at a loss for describing situations concisely and clearly.
I fully understand a neutral carries current back to the panel, that's its purpose, it's whole meaning in its little life. I was only trying to convey I never been bit by one before. My mistake here is that I was disconnecting each breaker one by one and failed to notice that one of the wires belonged to a 12/3 cable. I should have noticed that, but I did not. As a result, the other side of the hot (the red wire) that made up the 12/3 cable was still hot. I understand that. If I had gotten zapped by the neutral that belonged to the 12/3 cable I wouldn't be having this discussion because I would've reasoned that "oh I forgot to shut off the breaker feeding the other half of the 12/3 cable and whatever was on that breaker had a load on it at the time and that's why I got zapped."
But that was not the case. I wouldn't expect to get bit from the neutral wire of a 12/2 cable, a totally separate branch circuit as far as I'm concerned, AFTER I shut off the breaker to that 12/2 cable. Effectively, in my view that shuts off any possible load on that branch circuit and therefore I should not get zapped by the neutral because, it's a dead circuit. Yet that is what happened.
As a result of further investigating I fouind that the 12/2 cable ran into a j-box that the 12/3 cable happened to run into. The way the guy before me jerryrigged it I reasoned he must've somehow crossed the 12/2 cable in with the 12/3 cable when he did his splices. As a consequence, even though the breaker feeding the 12/2 cable was off, and because the other breaker feeding the 12/3 cable was still on, somehow the load from the 12/3 was being transferred to the neutral of the 12/2 circuit. When I shut off the breaker feeding the other half of the 12/3 cable then it caused the neutral in the 12/2 to go dead. It clearly seems to me the guy got his wires crossed somewhere, literally. If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
WW said:
I wouldn't expect to get bit from the neutral wire of a 12/2 cable, a totally separate branch circuit as far as I'm concerned, AFTER I shut off the breaker to that 12/2 cable. Effectively, in my view that shuts off any possible load on that branch circuit and therefore I should not get zapped by the neutral because, it's a dead circuit. Yet that is what happened.
That statement alone is reason you are doing something you have no understanding of and further discussion is futile. Either learn how electricity works or die. It's that simple.
"Only problem could be that the two breakers feeding the circuits are, by code, supposed to be tied together so if you turn off or trip one of them, the other is also supposed to turn off."Not true.What good practice, by code you only need a 2 pole breaker if if any single yoke (device) has both hot legs on it.And since the circuit that he is having problems with is a 12-2, plus ground, he does not have a shared circuit. At least not one by design, but he might have one by miss wiring.
Yes, this is helpful because you are correct, about the two needing to be tied together. Of course this is an old panel and wiring wasn't at the current code we have today or someone just didn''t know the code back then. Regardless, the situation here was indeed that on the 12/3 wire the two hots were on two totally separate breakers and they weren't side by side or tied together.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME