Open ground question

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Old 11-24-20, 09:36 AM
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Open ground question

I have an open ground circuit. Hot-Ground has 40V and Neutral-Ground has 30V at one outlet. They vary at another, if it matters. I am trying to locate the most upstream affected outlet with a circuit analyzer (3 light receptacle tester) and a circuit breaker finder. So far I found this circuit has 2 GFI receptacles for exterior outlets and bathroom outlets.

Question 1: If I insert the 3 light receptacle tester to an outlet downstream of GFI receptacle, will it still detecct open ground? Does GFI receptacle somehow affect the receptacle tester?

Question 2: If I push GFI TEST button, all outlets downstream of this should have no power, correct?

Question 3: In case the open ground is difficult to repair, can I install a GFI receptacle on the most upstream affected outlet and forget about this matter? Is GFI receptacle as good as grounded copper wire? What about lightning?

Thank you.
 

Last edited by paker; 11-24-20 at 09:57 AM.

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11-25-20, 09:49 PM
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If the circuit actually has a proper ground wire you should find the fault and repair it rather than tapping a ground from another circuit.
 
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Old 11-25-20, 06:14 AM
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1. The 3 light receptacle tester wil behave the same way, possibly giving the same false positive light patterns, whether inserted in to a receptacle upstream or downstream of a ground fault circuit interrupter. When an indicator light plug in circuit tester gives an "abnormal" readout, other tests, involving a multimeter, should be performed.

1a. The GFCI receptacle will not affect the tester but the tester, depending on how much current the indicater lights draw, may trip the GFCI.

2. Pressing the GFCI test button you should kill the power at the GFCI unit and within the subcircuit downstream connected to that GFCI unit's load terminals. Other outlets may exist that appear to be downstream from a GFCI and may be wired to the GFCI line side terminals and not be de-energized or receive protection from that GFCI.

2a. An additional GFCI within the subcircuit wired to the load terminals of a GFCI is nothing more than a waste of money. Pressing its test button might cause the other GFCI to trip instead.

3. A GFCI will work on a non-grounded circuit. A GFCI gives near perfect protection from accidenial electrocution but does not provide lightning protection or other protection that grounding provides.

3a. A separate ground wire (separate equipment grounding conductor) may be strung to ground (v.t.) an otherwise ungrounded outlet i.e. close the open ground. This wire may be strung exactly, approximately, or vaguely following the circuit conductors to the panel with the breaker for that circuit, which panel must be grounded, either already or using the technique in this paragraph. Should this wire first reach a fat ground wire (grounding electrode conductor) from a panel to a ground rod or to another proper grounding electrode or (new for 2014) first reach an outlet on a properly grounded circuit of the same or greater amperage, the separate ground wire may end and be attached there..
 
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Last edited by AllanJ; 11-25-20 at 06:52 AM.
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Old 11-25-20, 08:37 PM
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Thank you for answering all my questions. The last paragraph says I can tap ground from a nearby outlet. This may be my best approach. I will report back.
 
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Old 11-25-20, 09:49 PM
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If the circuit actually has a proper ground wire you should find the fault and repair it rather than tapping a ground from another circuit.
 
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Old 11-26-20, 06:03 AM
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Do you have 120 volts between hot and neutral?
 
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Old 11-26-20, 06:56 AM
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A 15 or 20 Watt incandescent test lamp, in the right hands, is far more instructive than the neon or led based plug ins.
wire one side to a firm 120v source, the other end is probed to ground points in the suspect circuit. These other testers are toys, IMO, mostly used by home inspectors to quickly find defects, but not to debug circuits.

One more comment; the EGC must be able to clear dozens of amps to clear a serious downstream fault. Commonly owned DMMís, plug in testers, even my test light, are not able to test this capability. The right tool is a ground bond tester, but at least the test lamp (not a neon model) is usually sufficient to find a major defect.
 
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Old 12-05-20, 11:58 PM
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Thank you for the advice. What I have found so far:

1. This circuit is the longest one. Of the 7 receptacles (including 2 exteriors) on the circuit, this is the closest to the panel, and is neither downstream nor upstream of any other receptacles. I know it because there were multiple GFCI's in this circuit. I suspect there is a junction box somewhere. I checked the attic but it had a foot of blown-in insulation. If there is a junction box, can it be in the wall? Or most likely in the attic?

2. I measured the resistance between the ground and another good ground. Infinite resistance, open. Neutral and Hot has 120V.

3. I did not connect the faulty ground wire to GFCI. As of now, no ground wire. The closest circuit from this bathroom outlet is the vent fan and light. I am not sure if I can tap ground from it.

4. I will test Hot-Ground with a light bulb and report back.

5. (unrelated) I found another receptacle with open ground, 120V receptacle tapped from 220V dryer connection. It is an old 3 wire dryer connection without ground. I installed a GFCI there. The washer connector is nearby but has good ground.

Any advice will be appreciated. Thank you.
 
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Old 12-06-20, 07:58 AM
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5. (unrelated) While you are at it, replace the breaker for that dryer circuit to be 15 amps if not already (or 20 amps if all of the wiring you added was 12 gauge or fatter).
 
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Old 12-06-20, 09:48 PM
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1. I want to repair the ground but cannot locate the other end. Is there a device that pros use to trace a wire back?

2. The dryer is on a 30A circuit breaker. Do you mean to replace it? I don't quite understand your advice.
 
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Old 12-07-20, 07:11 AM
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Yes. For a reason off topic to this thread.

You hung an ordinary 120 volt receptacle off of the dryer branch circuit. This is against code and/or invalidates the use of the branch circuit for the dryer.

The 120 volt ordinary receptacle may not be fed with a branch circuit not limited to 20 amps. Fourteen gauge wire may not be hung off of a branch circuit not limited to 15 amps.

I thought you stopped using the 30 amp circuit for a dryer when you installed the 120 volt receptacle. As an alternative to replacing the breaker with a 15 amp one you could remove the sub-ten-gauge wiring and the ordinary receptacle(s) from the dryer circuit and leave the 30 amp breaker in place..

Oh, by the way they make an electronic device, sometimes called a toner, used to trace wiring in the wall. You clip the tone generating device, perhaps shaped like a cigarette pack, to a wire end and use the hand held receiver, perhaps also shaped like a cigarette pack, to try to find the path of the wire in the wall.



 
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Old 12-09-20, 11:52 AM
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Thank you for the explanation. I didn't know the piggy back receptacle is code violation. I bet it was installed for gas dryer connection. Could it be code compliant when the house was built 30 years ago?

I will look for the wire tracer device. Thank you.


 
 

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