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#86679 - 11/19/03 05:25 PM Grounding method question
Jim M Offline
Member

Registered: 08/10/01
Posts: 453
Loc: Chestertown, MD, USA
I was just in a older (about 30-40 years) house that I think has metal framing. It appears that the wiring was 2 conductor NM. A ground wire has been run between the box and the device. It seems like they were using the framing to achieve the ground connection. A plug-in checker shows the devices are wired properly. I don't think that this is the way it should be, but don't have enough info to make an informed decision. What options should I tell the owner are available?

Thanks,
Jim

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#86680 - 11/20/03 02:25 AM Re: Grounding method question
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
first off~ this may have been compliant to the '63 nec....

secondly, there are newly marketed goodies to enhance the safety of older wiring, such as AFCI's

btw~ i would be very careful to offer anything more than 'enhancement' with these...

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#86681 - 11/20/03 04:01 AM Re: Grounding method question
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
I'm not a construction expert, but metal framing on a 30-40 year old house seems unusual.
Maybe the boxes are grounded but you can't see it. From behind?

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#86682 - 11/20/03 06:35 AM Re: Grounding method question
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
I would be very concerned if the framing of the house is used as an equipment grounding conductor...
_________________________
Ryan Jackson,
Salt Lake City

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#86683 - 11/20/03 06:20 PM Re: Grounding method question
stamcon Offline
Member

Registered: 03/24/01
Posts: 322
Loc: So San Francisco CA
Jim, some of the old houses I deal with, use a small(16 gauge?) bare copper wire that runs throughout the house, "connected" to the boxes by wrapping several turns around a nail that attaches the box to the stud. The wire would terminate at a water pipe with a strap. The wire is tee tapped, by wrapping the tap around the main wire and soldering, just like knob and tube wiring. Sometimes it's just the kitchen and bath that have the wire.

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#86684 - 11/21/03 10:20 PM Re: Grounding method question
PCBelarge Offline
Member

Registered: 06/08/03
Posts: 657
Loc: Dobbs Ferry, NY, USA
Using the structural steel, or a grounding conductor that is not run with the phase conductors may not ensure that the ground fault current path is effective.

250.4(A)(5) Effective Ground-Fault Current Path. requires this path to be effective, therefore that would not be a proper method.

I know that the code permits a grounding conductor to be run to the nearest equipment grounding conductor, 250.130(C), but I say this is asking for trouble.

Pierre
_________________________
Pierre Belarge

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#86685 - 11/22/03 08:08 AM Re: Grounding method question
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
 Quote:
some of the old houses I deal with, use a small(16 gauge?) bare copper wire that runs throughout the house, "connected" to the boxes by wrapping several turns around a nail that attaches the box to the stud
Stamcon,

I've seen that too, usually for Kitchens. Never seen Copper though, the ones I've seen seem to be Aluminum. They sometimes go from each device box up to the attic and are twisted together, or joined by some other questionable means. Many times these wires are cut or broken and not repaired simply because no one knows what they are.

I had some pictures around, but can't seem to locate them right now.

Bill

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#86686 - 11/23/03 10:56 AM Re: Grounding method question
electure Offline

Member

Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
Is there no ground wire at all?
All the metal boxes in my house were grounded with a bare #12 that was daisy chained from the back of one box to the back of another, then to ground in the service.
It wasn't run with anything else,just by itself. It apparently was Code compliant at the time ('58). I've seen lots done this way.

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#86687 - 11/25/03 10:14 PM Re: Grounding method question
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
Here's a Photo sent to me by Joe Tedesco showing a Ground wrapped around a nail:


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#86688 - 11/26/03 08:15 PM Re: Grounding method question
PCBelarge Offline
Member

Registered: 06/08/03
Posts: 657
Loc: Dobbs Ferry, NY, USA
Look at the nail going through the lower portion of the gem box.

Pierre
_________________________
Pierre Belarge

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