Ground wire issue


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Old 04-07-14, 06:45 PM
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Ground wire issue

I am adding some wiring in my game room and encountered a voltage on a ground wire. This house was built in 1964 and remodeled in 1979. Most of the house was wired with romex 12/2 with a very small ground wire (higher gauge, maybe 24). The 1979 remodel basically destroyed the wiring as far as code goes. The inspector did not catch this when I bought the house. Many wires were spliced in the attic without a junction box, just wire nuts and sometimes with the incorrect size wire nut. I have fixed many of these by adding a junction box. Some 14/2 with ground was spliced onto a circuit with a 20 amp breaker.

I was adding a light and an outlet to a tornado safe room I just added. I added a 4" junction box, ran conduit (1/2" EMT) to the safe room and spiced the wire in the new junction box and ran conduit to a outlet box to replace the outlet where I added the junction box. I grounded the junction box and conduit using the ground wire. The conduit ran close to a cold water copper pipe, so I was adding a rubber insulation between the conduit and water pipe and got zapped. Using a volt meter, there was 121 volts between the conduit and water pipe. I discounted the ground and the voltage was zero. I suppose this is a ground fault. How can I determine were the fault is located? I have tested all outlets that I know of by measuring between the ground on this circuit and the ground on a long extension cord plugged into a good circuit. The voltage has varied from 40 to 121. Is it possible to put a tone on the ground wire and trace where the fault lies? And suggestions are comments would be greatly appreciated. The safe room is in the game room.
 
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Old 04-07-14, 07:02 PM
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I would start by turning off circuits one at a time to find out which circuit is causing the problem and then turn that circuit off to see what goes dead to limit the search.
 
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Old 04-07-14, 07:07 PM
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Welcome to the forums!

The circuit you are taping off of, is that grounded correctly at the panel? Can you shut off the breaker and not get any voltage on any wire?

First thing I would do i make sure the water pipe is not the source of the voltage. Take your meter and measure between the neutral/ground bar and the water pipe. I do not know of any "tone" equipment so the best thing I can suggest to you after that is turn off the circuit and start taking apart anything that is dead and start looking for issues.
 
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Old 04-07-14, 07:25 PM
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Thanks for the quick responses. I have 400 amp service and the 2 main panels are grounded to the cold water copper pipe (per the inspectors request) which runs underground to my well house. So the copper pipe should not have voltage. When I turn off the breaker to this circuit, there is no voltage. The problem appears to be limited to this one circuit. I did plug a breaker finder (a device that sends a tone so you can detect which breaker controls the circuit) and no tone was heard at the panel box. A nearby circuit did have the tone at the breaker box. I did add a GFI outlet to the end of this circuit so I could plug in a pump to pump water off the pool cover. The outlets on this circuit have several items plugged in, but none use the ground, Samsung TV, Dish Joey (wall wart), my chop saw, computer monitor. All seem to work well.

Edit: I did remove the panel cover, and both the neutral (white) and ground (bare) are connect to the grounding bar.

Opps: the computer monitor does have a 3 prong plug, so the ground is used. 50 volts at this outlet.

Since the breaker is not being thrown, the ground wire must not be continuous back to the panel. (A novice's opinion) I have replaced most of the outlets on this circuit and the ground wire was cut as it exited the sheathing and not wired, so I had to splice a wire to properly ground the outlet. I must have an outlet I haven't found on this circuit. Probably hidden behind some sheetrock I haven't removed.
 

Last edited by spebby; 04-07-14 at 07:46 PM.
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Old 04-07-14, 08:32 PM
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The ground should play no part in the normal operations of the circuit. It should only carry voltage under a fault condition.
 
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Old 04-07-14, 08:59 PM
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Is your service panel a main breaker panel or a main lug panel? That is, does it have a main breaker in it that can be used to turn all of the power in your house off and on?

Some questions:
  1. If there's not a main breaker in your service panel, where is the main overcurrent protection device for your service?
  2. If there's not a main breaker in your service panel, are the neutral wires in it separated from ground?
  3. If there is a main breaker in your service panel, are the branch circuit neutral and ground wires bonded together in it, along with the incoming neutral and conductors going to rarth grounds such as your cold water supply pipe and driven ground rod(s)?
 
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Old 04-08-14, 06:01 AM
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Both main breaker panels have a 200 amp main breaker. Each panel has conductors from the meter to the panel. Turning these breakers off kills all electricity in the house. The ground and neutral are bonded together. The incoming neutral (wrapped in white tape) and the conductor running to both ground rods and the copper water supply pipe are bonded together. The electrician who added the second panel tried driving ground rods (3 ground rods) into the ground, but could only get them in about 3 ft. The city inspector then requested a conductor to the copper water pipe.

I need to move on with this project, so I am calling an electrician this morning. I will post the results of his/her visit.

Thanks for the quick responses.
 
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Old 04-09-14, 12:57 PM
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Problem solved. At first the electrician was as confused as I was because he isolated the problem to the same place I did, but no problem was found at that place. He did notice a Romex wire that I missed and that was the problem. I tore down some cedar planks and the wire went nowhere, just hanging between two studs. It was a 14-2 wire with no ground. The electrician removed about 2 feet of the sheathing and there was no ground wire. He removed the wire from the circuit and the voltage between the ground to the water pipe went to zero.
 
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Old 04-09-14, 02:38 PM
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Thanks for letting us know the problem was resolved.
 
 

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