I was reworking a panel today where I needed to seperate the gnd and neutrals. I was pulling off the gnd wires to install them on the gnd bar when boom I get shocked from one bare gnd to the other. It was a mild shock. I get out my wiggie and only read continuity. I get out the digital and I read 54 V from gnd to neutral on two differnt gnd wires ( while they are disconnected of course) I got 170V from the gnd to one of the phases. With the grounds hooked up the panel operates with no known problems. I think this is a potential hazard, but I dont know what it could be. The only thing I can think of is high resistance faults, but on multiple wires? I am still learning therory so could someone explain what is or could be happening here. Thanks in advance.
voltage on gnd wire.
- Thread starter jes25
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peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
Were you doing this with live circuits?
You could have an improper ground to neutral connection on one of those circuits.
You are probably reading a ghost voltage with your multimeter.
Were you doing this with live circuits?
You could have an improper ground to neutral connection on one of those circuits.
You are probably reading a ghost voltage with your multimeter.
peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
An outlet that got folded back into the box causing the ground to touch the neutral terminals is a common cause.
You can figure this out with both the neutral and ground disconnected from the bus bars on the circuit that gave you the shock. If you get N-G continuity, you have a wiring error somewhere.
An outlet that got folded back into the box causing the ground to touch the neutral terminals is a common cause.
You can figure this out with both the neutral and ground disconnected from the bus bars on the circuit that gave you the shock. If you get N-G continuity, you have a wiring error somewhere.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: voltage on gnd wire.
Is this one of those older houses (like mine) that still have a number of 2-prong receptacles? Sometimes the owner, hoping to get the computer's UPS to stop beeping at them (because it is not seeing a ground connection) will tie the N to the G within that receptacle.
Is this one of those older houses (like mine) that still have a number of 2-prong receptacles? Sometimes the owner, hoping to get the computer's UPS to stop beeping at them (because it is not seeing a ground connection) will tie the N to the G within that receptacle.
peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
If they are touching and there is a load on the circuit, the bare ground will be conducting neutral current.
If they are touching and there is a load on the circuit, the bare ground will be conducting neutral current.
Re: voltage on gnd wire.
I understand the parallel path issue. But my thinking says if there is an improperly connected bonding jumper between the N and G there would be current flowing on the gnd, but the voltage between N and G would be 0
I understand the parallel path issue. But my thinking says if there is an improperly connected bonding jumper between the N and G there would be current flowing on the gnd, but the voltage between N and G would be 0
peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
It can never truly be 0. There is always a slight voltage drop between the two.
It can never truly be 0. There is always a slight voltage drop between the two.
peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
Let me say that this second hand troubleshooting is very hard to do. It's impossible for me or anyone else to know what is precisely wrong without actually being there, observing the wiring and taking measurement. There are way too many subtle issues and variables involved.
You do have a problem. The devil is in the details though.
I think we can point you in the right direction though.
Let me say that this second hand troubleshooting is very hard to do. It's impossible for me or anyone else to know what is precisely wrong without actually being there, observing the wiring and taking measurement. There are way too many subtle issues and variables involved.
You do have a problem. The devil is in the details though.
I think we can point you in the right direction though.
peter d
Senior Member
- Location
- New England
Re: voltage on gnd wire.
That sounds like the strongest possibility based on the information you provided.
That sounds like the strongest possibility based on the information you provided.
Re: voltage on gnd wire.
jes25,
My concern would be,how did you leave this situation with,the customer,your boss,or your supervisor? The job is not finished until this has been corrected or at least reported to someone that takes care of such matters.Don't let your actions as an electrician hurt or even worse kill someone. My intention here is not to insult or belittle you in any way,it's all in the learning curve.
jes25,
My concern would be,how did you leave this situation with,the customer,your boss,or your supervisor? The job is not finished until this has been corrected or at least reported to someone that takes care of such matters.Don't let your actions as an electrician hurt or even worse kill someone. My intention here is not to insult or belittle you in any way,it's all in the learning curve.
allenwayne
Senior Member
Re: voltage on gnd wire.
Sounds like someome some time found an open neutral and grabbed a ground to get things going.With a load on that circuit there would be voltage as you found.I have seen this before and as we investigated this was wired in NM there was a pressure short that crossed the neutral and ground in a 3 wire cable.
Sounds like someome some time found an open neutral and grabbed a ground to get things going.With a load on that circuit there would be voltage as you found.I have seen this before and as we investigated this was wired in NM there was a pressure short that crossed the neutral and ground in a 3 wire cable.
allenwayne
Senior Member
Re: voltage on gnd wire.
I meant to post that the pressure short is another possibility
I meant to post that the pressure short is another possibility
stew
Senior Member
- Location
- federal way,washington
Re: voltage on gnd wire.
Try this. A dryer circuit that is the old 3 wire type wher the barae ground wire is both the neutral and ground path. The dryer door is open so the lite is on remove the "ground" and see how fast you light up.Hot to lite thru the lite out the "neutral" and back to you.110 volts. A shocking bit of trivia.
[ October 22, 2005, 09:53 PM: Message edited by: stew ]
Try this. A dryer circuit that is the old 3 wire type wher the barae ground wire is both the neutral and ground path. The dryer door is open so the lite is on remove the "ground" and see how fast you light up.Hot to lite thru the lite out the "neutral" and back to you.110 volts. A shocking bit of trivia.
[ October 22, 2005, 09:53 PM: Message edited by: stew ]
mark32
Senior Member
- Location
- Currently in NJ
Re: voltage on gnd wire.
Years ago, early in my career, I came across a junction box in someone's attic in which the bare grounds and grounded conductors were tied together. Never before and even to this day have I ever seen this. Was this ever a popular way of running circuits?
Years ago, early in my career, I came across a junction box in someone's attic in which the bare grounds and grounded conductors were tied together. Never before and even to this day have I ever seen this. Was this ever a popular way of running circuits?
allenwayne
Senior Member
Re: voltage on gnd wire.
Not in the past 32 years that I know of anyway.
Not in the past 32 years that I know of anyway.
Re: voltage on gnd wire.
I know you are 100% well meaning but to suggest this is my fault or problem i dont agree with. This was pre existing problem that I discovered that has been there for no telling how long. I reported the problem to the customer and told him I would research it and get on it this week ( which is hard enough with my already packed schedule). If I can not find the problem I will suggest he call someone else. I can not accept a 60 year old houses problems as mine, the problem is the customers my job is done when I report it to the owner.
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