Customer called said got a shock from refrigerator, I went to the house and had 120v from outside of refrigerator, also had 120v from microwave and vent hood on stove. All are on the same circuit. There is no ground on any of these outlets as there a 2 wire system. This circuit in the panel board is a 3 wire circuit and the ground is landed. Checked amperage on the ground to ground rod and it's 0 amps, amperage on water meter bonding is 1.5 to 6 amps. With the complete house main shut off I still get over 1 amp on the water meter ground. I'm confused as to what might be the issue?
Appliance has 120v to shell
- Thread starter Robbiedo
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
So all appliances have 3 prong plugs and 3 prong outlets? In that case one of them is shorting to ground and carrying it to the other appliance. Don't worry about the 1 amp from ground with the main off. I am guessing it is voltage perhaps coming from community water system, if there is one.
All appliances have 3 prong plugs and 3 prong outlets. This is a 2 wire system with no ground wire. I installed a GFI breaker for the circuit in the panel, plugged each appliance in separately ( one at a time ) and each one had 120v on the shell of the appliance. The polarity on each outlet is proper.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
My number one question: What changed recently? This cannot have been going on for years. Someone must have done something with a receptacle, a circuit breaker in the panel, or some other aspect of the electrical system. Is is a safe bet that as soon as that change was installed, the problem was created. So find out what that change had been, and look there first.
If the fridge has a 3-prong plug, and if it is plugged into a grounded-style receptacle that does not have a ground wire attached to it within the outlet box, then what happened to the ground wire that you say is landed within the panel? My guess is that two wiring errors were made, but only one need have been made recently. One error is that a hot and neutral were reversed in a receptacle (like Hv&Lv suggested), and it would have to be a receptacle at, or upstream of, the first of the appliances on this circuit. The other error is that in order to fool some component into believing it had a ground wire available, someone connected a neutral screw to an equipment ground screw on a receptacle. That second thing (the N-G connection) might have happened long ago, without anybody noticing. But it was only when that other error (H-N reversal) was recently made that someone felt a shock. You may need to look in more than one place, to find both wiring errors.
If the fridge has a 3-prong plug, and if it is plugged into a grounded-style receptacle that does not have a ground wire attached to it within the outlet box, then what happened to the ground wire that you say is landed within the panel? My guess is that two wiring errors were made, but only one need have been made recently. One error is that a hot and neutral were reversed in a receptacle (like Hv&Lv suggested), and it would have to be a receptacle at, or upstream of, the first of the appliances on this circuit. The other error is that in order to fool some component into believing it had a ground wire available, someone connected a neutral screw to an equipment ground screw on a receptacle. That second thing (the N-G connection) might have happened long ago, without anybody noticing. But it was only when that other error (H-N reversal) was recently made that someone felt a shock. You may need to look in more than one place, to find both wiring errors.
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- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
It would help if you could tell us how you know this. Is it because the black and white wires are landed on the correct locations on each receptacle? Or is it because you used one of those 3-light plug-in testers, and it told you the wiring was correct? If the former, then the wiring error is upstream of the recepacles you looked at. If the later, then did it show the lighting pattern associated with an open ground?
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Can not find where it switches from 3 wire to 2 wire. There are 2 j-boxes in the attic but it goes down to the basement as a 2 wire then in the basement it changes to a 3 wire. Might be a j-box in the wall somewhere I can not find, which I not is not code. I checked each outlet with the outlets out of there box, not a plug in tester. I am not sure what changed recently, I will ask the customer in the morning.
Removed all receptacles starting from the farthest to the closest, the closest one still has 120v on the appliance shell. Tried 3 different appliances, homed out appliances, there good, plugged them into other receptacles and they work fine. Going to run a new wire from panel board to first recepticle and see what that does? Have never had this issue arise before but there is always a first I guess.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
If you unplug everything do you get normal readings? Something is wired wrong somewhere. Start splitting the circuit in half and work from there.
Ran new wire from PB to GFCI receptacle, didn't hook up ground to receptacle, plugged in appliance still has 120v to shell. Hooked up ground on receptacle and voltage is gone?? On 2 wire systems code states it is acceptable to replace 2 prong outlets with 3 prong GFCI, but in this case it does not seem to work. Any ideas??
If I understand this correctly, you connected a new receptacle, with no ground wire connected to the receptacle ground . So there cannot be a voltage on the ground with nothing plugged in. When you plug in the appliance, you get a voltage to neutral (from another circuit) on the shell. The shell should be connected to the ground prong on the cord. The only way you could get voltage is to have a connection from the hot wire to the shell, inside the appliance. This would cause a short-circuit when plugged into another receptacle, which it didn't. This leads me to believe that there is a neutral to ground connection inside the appliance and that there is a polarity error in the wiring to the new receptacle. When you plug the appliance into the new receptacle, the shell is connected to the hot wire. When you plug the appliance into another receptacle, the shell is connected to the neutral.
Is there voltage between the neutral of the new receptacle and the ground of another receptacle that has a ground wire?
Is there voltage between the neutral of the new receptacle and the ground of another receptacle that has a ground wire?
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Let me make sure I understand the present situation. Do I have this right?
- You ran a new, 3-wire circuit (black, white, green) from the panel to an outlet box.
- You connected the black wire to a breaker (perhaps the same one from the original suspicious circuit, perhaps a new breaker).
- You connected the white wire to the panel?s neutral bar.
- You connected the green wire to the panel?s ground bar.
- At the outlet box, you connected the black and white wires to a GFCI receptacle, but at first left the green wire dangling in the outlet box.
- You plugged in one of the appliances (which one, by the way?).
- You measured 120 volts from the frame of that appliance to the neutral of some other, nearby circuit.
- You then connected the green wire to the GFCI receptacle, and plugged the appliance back in.
- The 120 volts from the frame is no longer there.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
That is how I read it also.
dpeter
Member
- Location
- Indianapolis, In.
- Occupation
- elevator mechanic / building maintenance
My bet is it is the defrost element in the fridge shorted to ground far enough from the line side so as not to trip the breaker but still energise the shell.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Except that the op states each individual unit does the same--
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
The OP also said this:
Possibility number 1 would make sense if some wiring work was recently done, and if the customer's initial report of being shocked happened immediately thereafter. But if the OP installed new wire, and if there was still 120 volts on the outer shell of the appliance, and if the 120 volts disappeared when the ground wire was connected, then this will not explain the situation.
Possibility number 1 might also make sense if there had been an undetected wiring error from the past, and if the thing that recently changed was that the appliance had an internal fault, as has already been suggested. Here again, pulling a new circuit that is completely independent of the original circuit would tend to discredit this possibility.
Possibility number 2 is worth discussing, I believe. The OP said he measured to another circuit's neutral. I am curious as to why. I mean why not measure to the neutral of the circuit being tested? And which other circuit was used for this measurement?
If the outer shell of three items have voltage on them, and if there is no ground wire (or, I infer, no metal conduit) that would otherwise bond the outer shells to each other, then where can the point of common failure be? Only two possibilities come to my mind.
- Somewhere in the circuit there is a wiring error, or
- There is something incorrect about the way the 120 volts is being measured.
Possibility number 1 would make sense if some wiring work was recently done, and if the customer's initial report of being shocked happened immediately thereafter. But if the OP installed new wire, and if there was still 120 volts on the outer shell of the appliance, and if the 120 volts disappeared when the ground wire was connected, then this will not explain the situation.
Possibility number 1 might also make sense if there had been an undetected wiring error from the past, and if the thing that recently changed was that the appliance had an internal fault, as has already been suggested. Here again, pulling a new circuit that is completely independent of the original circuit would tend to discredit this possibility.
Possibility number 2 is worth discussing, I believe. The OP said he measured to another circuit's neutral. I am curious as to why. I mean why not measure to the neutral of the circuit being tested? And which other circuit was used for this measurement?
kwired
Electron manager
- Location
- NE Nebraska
Some possibilities or assumptions:
two wire (no EGC) circuit
has had extensions made to it with three wire cables and grounding type outlets were installed, these grounding type receptacles have their grounding terminals connected together but are not supplied with an EGC therefore something happens that raises the voltage on one and they all have same problem because they are tied together but not grounded.
another possibility is same as above but they did attempt to ground it by connecting the added grounding conductors to the neutral someplace. Now you have some resistance someplace on the neutral and it is bringing the jack legged EGC to the same potential as the neutral it is tied to.
Don't know for sure what you have but these are some possibilities.
two wire (no EGC) circuit
has had extensions made to it with three wire cables and grounding type outlets were installed, these grounding type receptacles have their grounding terminals connected together but are not supplied with an EGC therefore something happens that raises the voltage on one and they all have same problem because they are tied together but not grounded.
another possibility is same as above but they did attempt to ground it by connecting the added grounding conductors to the neutral someplace. Now you have some resistance someplace on the neutral and it is bringing the jack legged EGC to the same potential as the neutral it is tied to.
Don't know for sure what you have but these are some possibilities.
OK here is an off the wall possibility. I say off the wall as I am not sure it is ENTIRELY possible.
The conductors are running the metal shell of the appliances that should be grounded but are not.
This WILL induce SOME voltage, I am sure it will induce some, but 120V not so sure.
By properly grounding it this will go away.
So my next question is what are you measuring the voltage with, wiggy, digital VOM, analog VOM., neon or other??
One can get shocked by far less than 120v especially with soft wet skin.
Regardless of the cause you have already stated the cure to be connecting a proper ground. IMO I would run a new feed to these outlets and double check them all.
Please let us know of anything else you find.
The conductors are running the metal shell of the appliances that should be grounded but are not.
This WILL induce SOME voltage, I am sure it will induce some, but 120V not so sure.
By properly grounding it this will go away.
So my next question is what are you measuring the voltage with, wiggy, digital VOM, analog VOM., neon or other??
One can get shocked by far less than 120v especially with soft wet skin.
Regardless of the cause you have already stated the cure to be connecting a proper ground. IMO I would run a new feed to these outlets and double check them all.
Please let us know of anything else you find.
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