Open ground problem

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  #1  
Old 11-18-18, 06:28 PM
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Open ground problem

One circuit in our house has a ground problem. A receptacle tester says "open ground" on all of the receptacles in this circuit EXCEPT ONE which shows normal voltages. The bad receptacles all show 120V hot/neutral but 60V from neutral/ground and hot/ground. If I use a cold water pipe as a ground instead of the circuit's ground, I see 120V between hot and ground. The good receptacle on this circuit shows 120V neutral/hot and hot/ground and 0V neutral/ground.

I have replaced nearly all of the receptacles. Several of the ground wires in the junction boxes were twisted together with pliers and had no wire nuts or connector. The house and circuits are about 45 years old.

How can I find the location of the open grounding problem?

Thanks so much!
 
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Old 11-18-18, 06:57 PM
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Where is the one receptacle that shows normal voltages, is it the first receptacle on the circuit, the last or somewhere in the middle. I can say for sure that you have a problem in either a junction box or at one of the receptacle boxes. I think I'd pull all devices and renew all connections/wirenuts and reinstall the receptacles on the side screws. Do the same at junction boxes.
 
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Old 11-18-18, 07:05 PM
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Those plug-in testers are easily confused.
You don't have an open ground...... you have an open neutral.

Use a lamp to see if you have normal 120v when you plug the light in to the receptacles in question.
They should work normally with no ground present.
 
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Old 11-18-18, 07:08 PM
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Those plug-in testers are easily confused.
I also assumed the OP was using a plug in tester, but also assumed he was also using a meter of some type since he posted actual voltages. I believe there may be more than one problem on this circuit from too many inexperienced DIYers.
 
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Old 11-18-18, 07:44 PM
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"Those plug-in testers are easily confused.
You don't have an open ground...... you have an open neutral."

Is it possible to detect and locate the "open neutral"? Did you identify the open neutral from my voltage readings?

"Use a lamp to see if you have normal 120v when you plug the light in to the receptacles in question. They should work normally with no ground present."

All receptacles work OK when tested with lights. All receptacles have 120V between hot and neutral. Do the receptacles and lights function normally with open neutral?

Thanks!
 
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Old 11-18-18, 07:48 PM
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Not sure where the good receptacle is located in the circuit but it has more than one hot and neutral wired to the receptacle.

Is it possible to narrow down the location of the problem or is re-establishing all connections the only way?

Thanks!
 
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Old 11-19-18, 03:01 AM
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Moogy, so far you have done it right, and given lots of good information. Even when I'm living in another country with a different power system this are well explained.
I guess you have looked at the ground wire connection on the outlet, and that is good, and you hva used the very same terminal when you connected the ground from the water pipe, doing this will eliminate the risk having something wrong in the receptacle it-selves. The next is to examine the ground wire close to the receptacle, if it is OK. The next will be to find the last box or point the same wire is coming from, and testing there. If you are able to measure the resistance between the 2 points (roughly) you may find if the cable are OK or not. If the ground wire are damaged, one of the others may be more or less good too.
 
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Old 11-19-18, 08:47 AM
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Dear DSK: Thank you very much for the useful info. Could I please ask you to confirm if this is what I should do:
(1) Use a (long) wire attached to the water pipe as ground and check each receptacle to see if there is 120V between hot/neutral, 120V between hot/ground and 0V between neutral and ground. This will show if there is if the receptacles are wired correctly.
(2) Check for continuity of the ground using a multimeter to measure the resistance between two receptacles. There should be continuity between receptacles if the ground is intact.

Questions: (a) can I check the junction box by screwing a receptacle adapter (screws into light bulb socket and has hot and neutral receptacles) or should I measure the junction box connections directly as above? (b) there are several lights on the bad circuit - should I check their switches too?

Thank you very much. I apologize for not being able to be clearer about the task and requirements.
 
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Old 11-19-18, 08:58 AM
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1) Yes!
2) Yes!
a) Give it a try, keep the lamps mentioned in b) on, a load makes the situation real.

If that works, we stop there :-)
 
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Old 11-19-18, 09:06 AM
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Thanks! I will try these tasks today and let you know. Thanks again!
 
 

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