I'm renovating an old building and discovered that the existing branch circuit wiring for the light fixtures and receptacles is two-wire (hot and neutral) BX or AC cable. The receptacles are 3-prong outlets. NEC 250-118 seems to allow AC cable as an equipment ground. Is this correct? Is a bonding jumper required between the outlet box and grounding screw on the receptacle? How about to the light fixtures?
Grounding receptacles on two-wire systems
- Thread starter rnolan
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Grounding receptacles on two-wire systems
Depends on the type of AC cable, is it per Article 320? An older cable may not have the internal bonding strip.
I suggest you use the GFCI provision in 406.3(D)
Depends on the type of AC cable, is it per Article 320? An older cable may not have the internal bonding strip.
I suggest you use the GFCI provision in 406.3(D)
- Location
- Illinois
- Occupation
- retired electrician
Re: Grounding receptacles on two-wire systems
Celtic,
The neon glow tester will glow without out a good EGC. You have to verifiy what is being used as the EGC. Just because you can light a neon tester or even a solenoid voltage tester does not mean that the grounding path is suitable for use as an EGC.
Don
Celtic,
The neon glow tester will glow without out a good EGC. You have to verifiy what is being used as the EGC. Just because you can light a neon tester or even a solenoid voltage tester does not mean that the grounding path is suitable for use as an EGC.
Don
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: Grounding receptacles on two-wire systems
How old is the wiring? BX or type AC cable started using the required bonding strip around 1959. The metallic armor may be an approved EGC. If so, this would allow you to use a self-grounding receptacle with the 2 wire cable or a bonding jumper between the device and the box.
How old is the wiring? BX or type AC cable started using the required bonding strip around 1959. The metallic armor may be an approved EGC. If so, this would allow you to use a self-grounding receptacle with the 2 wire cable or a bonding jumper between the device and the box.
Similar question
Similar question
Lets take this one step farther. Old 2 wire RX (romex) obviously no grounds, can you install a supplemental ground wire from basement up to receptacle and box? What do they get terminated to in the basement? The closest water pipe? The Water service street side of the meter? Or does it have to run into the panel box attached to ground bar ?
Similar question
Lets take this one step farther. Old 2 wire RX (romex) obviously no grounds, can you install a supplemental ground wire from basement up to receptacle and box? What do they get terminated to in the basement? The closest water pipe? The Water service street side of the meter? Or does it have to run into the panel box attached to ground bar ?
- Location
- Illinois
- Occupation
- retired electrician
Ram,
Take a look at 250.130(C).
Don
Take a look at 250.130(C).
Don
pierre
Senior Member
- Location
- Westchester County, New York
I am not too sure how effective the ground fault path would be when using 250.130(C). I have never really liked that section.
I guess this is one of the times that one does not have to follow 300.3(B).
What do some of you think about it.
I guess this is one of the times that one does not have to follow 300.3(B).
What do some of you think about it.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Pierre, my vote: it's better than nothin'. 
That suprised the both of us.
We were working in an existing basement, and added a receptacle to a concrete wall. My coworker hammerdrilled two holes in the concrete, installed the plastic anchors, mounted the metallic box, and then tested from a hot conductor to the box. The tester glowed, with only the tiny connection where the screws damaged the anchors as they were installed.Don said:
That suprised the both of us.
- Location
- Illinois
- Occupation
- retired electrician
George,
Back when I did do some residential service calls on knob and tube systems, I would use the neon tester to identify the hot...just hold one lead in your hand and touch the other lead to the conductor.
Don
Back when I did do some residential service calls on knob and tube systems, I would use the neon tester to identify the hot...just hold one lead in your hand and touch the other lead to the conductor.
Don
Lets hear how everyone is doing that.. Please Examples go along way...
Back 20 yrs ago when I was an apprentice, the guy I was working with said " You take all the new individual #12 ground wires, bring them to a central point, and mount a Ground Bar then take a #6 thhn copper wire and run to to the street side of the water service." He said that works and an inspector had never turned him down. Until now I have never needed to add ground wires.. I did mostly commercial / industrial wiring..
Any thoughts or better ideas would be helpful..
Thank You
Roger
Back 20 yrs ago when I was an apprentice, the guy I was working with said " You take all the new individual #12 ground wires, bring them to a central point, and mount a Ground Bar then take a #6 thhn copper wire and run to to the street side of the water service." He said that works and an inspector had never turned him down. Until now I have never needed to add ground wires.. I did mostly commercial / industrial wiring..
Any thoughts or better ideas would be helpful..
Thank You
Roger
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
See 250.120(C).jes25 said:
The only catch is verifying that the electrical service does have a GEC connected to the water service. That's something that isn't explicitly spelled out, and something that something that can get overlooked with "grounding" being what the installer is oriented toward, instead of "bonding".RAM460 said:
The guy you were working with was better than the ones I was working with. We (wrongly) ran a 12 AWG conductor to the water pipe under the kitchen sink, or elsewhere convenient, and quit there. To use the water pipe electrode, you have to catch it within 5' of the building entrance (250.52(A)(1)). Coming to this forum straightened me out on that practice.
peter d
Senior Member
- Location
- New England
RAM460 said:
Are these bonded to the service grounded conductor along the way?
There is a new unbroken Ground wire from the Main electrical service to the street side of the water meter, then jumped back to the house side of the water meter. Well apparently it is ok. The inspector looked it all over said it looked good to him, better than what a lot of guys try. He passed it no problem. I don't know if working off the 1999 NEC makes a difference, thats all they have adopted here.
Thanks for all your input
Thanks for all your input
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