1945 2 wire electrical system


Old 11-23-04, 08:17 AM
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1945 2 wire electrical system

I just purchased a 1945 home with a 2 wire system. I want to convert all the 2 prong outlets with 3 prongs. I purchased the self-grounding outlets and was told they don't need a ground wire to be grounded, but when I test them, I get OPEN ground. Do I still need to attempt to ground the outlets to the box or am I just wasting my time without a 3 wire system?
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Old 11-23-04, 08:26 AM
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Self grounding outlets will automatically make electrical contact to metal boxes when installed properly. If the metal box is properly grounded, then the outlet will be grounded. If the metal box itself is not grounded, then a self grounding outlet will not create the ground connection.

What sort of outlet boxes do you have?

What sort of cable/wires run to these boxes?

If you have AC cable (sometimes called BX, or armor clad), then the cable armor should be the equipment ground conductor, and you will simply need to figure out where this ground is broken.

If you have old NM cable (Romex; the old stuff had a woven cover), then you have no equipment ground conductor. In this case you either have to stick with two prong receptacles, or install GFCI receptacles. GFCI receptacles in this application are still 'open ground', but the GFCI provides the necessary personal protection. The third option is to run new circuits.

Old 11-23-04, 09:11 AM
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self grounding outlets

I have the old NW cable with the woven sheath. The outlets are metal boxes and I guess I need to put a continuity tester on there to see if the box is grounded.

If the box is grounded and I use the self grounding outlet and it still isn't grounded, does that mean I am doing something wrong. Can I add a ground wire from the box to the outlet?
Old 11-23-04, 09:17 AM
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
If you have the old NM cable, then it is pretty certain that you don't have grounded boxes. You are limited to using two prong receptacles, using GFCI receptacles, or installing totally new cable.

Old 11-23-04, 10:06 AM
Join Date: Sep 2000
Location: Fayetteville, NY, USA
Posts: 1,052
The NEC permits you to replace 2-prong receptacles with 3-prong receptacles ONLY if the 3-prong receptacles are GFCI-protected and ONLY if each GFCI-protected receptacle bears a label that says "No Equipment Ground".

By GFCI-protected, I do not necessarily mean that each receptacle is a GFCI type. That could get expensive. If you have a string of receptacles and you want the entire string to be GFCI-protected, the first one in line (electrically - the closest one to your electrical panel), you connect the incoming juice (from the panel) to the "line" side of the GFCI type recep, then connect the wiring that continues on to the rest of the receps on that circuit to the "load" side of the GFCI type recep. All the receptacles downstream will now be GFCI-protected. And each one, if they were replaced with 3-prong receps, must be labeled. Some brands include a sheet of little labels for the purpose of identifying which receptacles are GFCI protected.

Winnie is right, though, this will not "create" a ground, but the GFCI will protect people from shock.

I had such a house. It had bad walls. Because of that, and the fact that I'm good with drywall and patching, I had no problem with the prospect of busting holes in the walls to run new wiring. So I ran new NM-B (Romex) cable with ground to all my new 3-prong receptacles. That's the ideal situation. But it's not for everybody. So GFCI is a good compromise that is code-compliant.

Hope that helps.

Old 11-23-04, 03:27 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
The best course of action for you to do is as follows:

Install only two prong receptacles in most places.

Install GFCI receptacles where you think you may need to use a three wire non-electronic device. Also install GFCI receptacles in the bathrooms, unfinished basement, garage, outside and kitchen.

Properly ground any receptacles where you will install electronic equipment that needs a good ground, and then use three prong receptacles.

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