Non-grounded wiring off grounded wiring?

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  #1  
Old 01-23-06, 05:05 PM
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Non-grounded wiring off grounded wiring?

One more room to rewire... Woohooo!!!

Situation - 1956 house - guest bedroom receptacle under a window on a plaster on cement board on firring on concrete block wall. Feed comes from jb in attic crawl space down beside the window then hangs a right over to the receptacle about 5 feet away. It ends there.

I intend to install a new receptacle roughly where the feed comes down, and hope that if I get my measurements right, I might hit where that existing cable turns to go across and be able to pull new NMB into the under window location. I've had good luck pulling in new cable with the old on a vertical run - most of the time. Existing wiring isn't stapled, but sometimes it jogs sideways - into a different stud space. Doesn't move then. But what if I can't get new wire to the existing receptacle location...

Would it be permissable to attach the existing wiring from this (two slot) receptacle to the new (grounded) circuit? Or would I need to maintain the existing circuit all the way back to the panel?

Existing wiring is 12 ga, as is the new. Thoughts? Comments?

Thanks!!!
 
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  #2  
Old 01-24-06, 09:43 AM
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The Issue; extending a circuit from an existing outlet-box with an indefinite provision for a Grounding connection.

The type of cable that terminates in the existing O-B will determine the arrangement for a Code-complaint connection. If the existing cable is Armored Cable, or a Non-metallic cable with a bare Grounding Conductor, than an approved Grounding-path is available at the extension-point.

A Non-metallic cable with ONLY two insulated requires connecting the existing conductors to the "Line" terminals of a GFI-type receptacle, and the conductors of the cable extending from the O-B to the "Load" terminals.

Good Luck, & Learn & Enjoy from the Experience!!!!!!!!!
 
  #3  
Old 01-24-06, 01:16 PM
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Thanks PATTBAA!

But when I think about it, in the one scenario, I am essentially "adding" the existing receptacle to the new three wire circuit so there's no way the two wire nm can be compliant.
 
  #4  
Old 01-24-06, 01:39 PM
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It would be a whole lot easier to install the 2-wire receptacle in a wiremold extension box and run wiremold to the new location. Your proposed method will require you to cut the wall open before you even know if your plan will work. What if you miss the wire running down the wall? What if you can't fish a new wire between the old and new receptacle locations? If possible, can you fish a wire down from the J-box in the attic to the new location, instead of tying into the old recpetacle.

BTW, what I prefer to do in old houses is locate the first receptacle (closest electrically) to the panel and replace it with a GFI receptacle. Use the load side screws to extend to the rest of the circuit and then you can replace all of the old receptacles with shiny new 3-prong receptacles.
 
  #5  
Old 01-24-06, 05:12 PM
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Thanks mcjunk,

GFCI's are a good thing, so don't get me wrong. I understand the use of a GFCI to accomodate three prong plugs in two wire circuits is legal and is in fact safer than the original two slot receptacle in nearly all circumstances.

But IMHO, the three prong plug is meant to attach to an equipment ground. Everything with a three prong plug presumably requires an equipment ground for user protection, electrical surge protection and/or true ground reference or some other reason. Otherwise, why is it there? If the equipment ground is not factored in somewhere in the design, a polarized two prong plug would be cheaper, work just fine and be just as safe as far as using the equipment is concerned. I'd have to do some research on UL listings that I don't have time for, but I would venture a guess that if it comes with a three prong plug, the UL listing is only valid if it is connected to an equipment ground. For whatever that's worth.

As far as missing the wire coming down from the attic... I'm not concerned about that (yet). I drill a tiny hole in the ceiling (maybe more than one if I hit a ceiling joist) - 6" from the wall and stick a piece of bare 22 ga up through the hole if I'm locating an existing or new o/b in a stud space, or down from the attic where the cable goes down the wall in this case. I've replaced every o/b in this house so far and added some - especially in the kitchen - boy did that take some extra holes!!! Smooth plaster there though - easy to repair...

Wiremold is great - I just don't need to use it in this case. I have the time and ability to bring the new cable to that receptacle (and patch the holes).
 
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