Partial Ground Receptacle Fix

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360Youth

360Youth

Senior Member
Location
Newport, NC
We sent a guy to a service call where the home owner had some receptacles not working. He found a bad connection in one of the boxes and got the circuit working again with the exception that he is only getting 90v to ground. I was wondering if 406.4 (D)(2)(b) would apply until the circuit could be more thoroughly diagnosed even though the existing devices are 3-wire? Does it only apply to two-wire circuits and devices? What is an acceptable line voltage-to-ground?

(D) Replacements.
(2) Non?Grounding-Type Receptacles. Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with (D)(2)(a), (D)(2)(b), or (D)(2)(c). See related UL
(a) A non?grounding-type receptacle(s) shall be permitted to be replaced with another non?grounding-type receptacle(s).
(b) A non?grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s). These receptacles shall be marked ?No Equipment Ground.? An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.
(c) A non?grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter. Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked ?GFCI Protected? and ?No Equipment Ground.? An equipment grounding conductor shall not be connected between the grounding-type receptacles.
 
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GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
360Youth said:
120v
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If line to ground is 90 and line to neutral is 120, then (except for vector effects which might make it worse) you have 30 volts neutral to ground. Most likely the ground is not really grounded and you are just measuring capacitive current. This is OK as long as the three wire GFCI protected receptacle is clearly marked "No ground present" and is a replacement for an original two wire receptacle.
 
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southsko

New member
Location
94002
GoldDigger said:
This is OK as long as the three wire GFCI protected receptacle is clearly marked "No ground present" and is a replacement for an original two wire receptacle.
Click to expand...

I think the language is "No Equipment Ground" and you should have some stickers inside the GFI box that say that.
 
360Youth

360Youth

Senior Member
Location
Newport, NC
raider1 said:
Check the main bonding jumper, it seems like this system is not properly grounded.

Chris
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The house panel is a rat's nest and located behind the office desk ( :happysad: ) and were not able to get to all of it. It will be at least Monday before we can back to the job.
 
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GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
360Youth said:
The house panel is a rat's nest and located behind the office desk ( :happysad: ) and were not able to get to all of it. It will be at least Monday before we can back to the job.
Click to expand...

Until then, the outlet may not be safe to use with appliances which connect the grounding wire to the shell or exposed metal parts of the box. It depends on whether there really is no ground or there is a ground wire which is at an elevated voltage.
 
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hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
Your going to have to find out if this house originally had a grounded system, looking in the main service panel could give some clues but if it had been changed out and relocated you could have new conductors in it feeding old two wire circuits elsewhere, if the house is all in conduit or again conduit just in the panel but the receptacles are old two wire then you don't have a complete path for a fault, as to your question of how much voltage is allowed from a hot to ground, well you should always have the full circuit voltage no matter what since the EGC should not have any current on it the EGC should always reference the same potential that you would have at the panels MBJ any voltage other then the full circuit voltage is a clear sign that you do not have a complete circuit.

As for the 90 volts as Gold Digger pointed out the voltage that was read is most likely what many call ghost voltage cause by capacitive coupling between the EGC and other conductor in a cable of conduit, using a DVM type meter that doesn't load down the circuit can give you misleading readings this is why some manufacture like Fluke now have meters with a load switch to load the circuit with a 1k ohm resistor that will drain off any ghost voltages so you will know what you actually have, solenoid type voltage meter such as a wiggy or the Ideal Volt-Con do this with the load of the solenoid in the circuit.

If you find that the house is new enough that the wiring should be of the grounding type, then your going to need a way to find the lost connection in the EGC, some times its just a split and divide type of search, circuit tracers can be of help in speeding up finding the bad connection but using one will require to load the EGC down so you will have a true open across the bad connection.

The problem with these kind of problems is trying to sell the importance of finding the problem to the home owner from a safety aspect, as since the lost voltage problem has been fixed many will just say that they don't want to spend any more on it or ask how much it will cost and since you will have no idea how long it will take to find it, they can get a little testy because like me I want to know how much something is going to cost before I spend my money and you can't blame them, if you want to use it as a learning experience then you could offer a price that you won't go over but if your paying a guy by the hour then that is hard to do in these days, but finding these kind of problems can be a good learning experience for both you and your workers, as well as making a customer happy they have a safe electrical system, which could get you more work down the line, I know I had many repeat customers because I would go out of my way to make sure I fixed anything unsafe, and many people are so afraid of electricity that when someone goes out of their way to make sure they have a safe system they like it.
 
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