Converting 2 prong to 3 prong

[jtfoxman]

About 1/3 of my house still has the 2 prong outlets in it. Should I change them to the 3 prong self grounding outlets or keep them? Just wondering about the safety of the 2 prong and the 3 prong self grounding.
Also what is the difference between a 3 prong grounding and a 3 prong self grounding?
Thanks all.

[Phelps]

I have never heard of a self grounding outlet before. That is a new one on me, and I hope someone else comes on here.

Regarding what is code, I believe it is okay that if you have 2 wires only, that as long as you use 2-prong plugs (they cost me $1.25 ea instead of the 44 cent for the 3-prong jobbies), in areas that normally don't require a ground ...say in the living room or bedrooms that are just going to be using 2-prong plugs (no computer), that this would be fine. I know that our local inspectors approve this when houses I maintain get inspected. And THEY are fussy!

[kactuskid]

In order to install a 3 prong receptacle you MUST have a ground in the box, otherwise you can install a GFCI receptacle. This will provide a 3 prong plug but still will not provide a ground.

If the cable that supplies power to the receptacle box is armored cable then a ground MAY exist in the box. To tell you need to buy a neon bulb voltage tester or a multimeter. You measure between the hot wire and the metal box. If you get either 120 volts or a light on the tester then this indicates a ground is present in the box. Then you can install a 3 prong self grounding receptacle in place of the 2 prong. Self grounding receptacles are sold at Home Depot and indicated on the box to be self grounding. If you want to install a regular 3 prong receptacle and not the self grounding type, then you must pigtail a ground wire to the box using a 10-32 screw.

Your other option is to run a new circuit to the living room that has a ground and install a new 3 prong receptacle.

Here's a link that'll explain all of this to you and under what conditions you can replace a 2 prong with a 3 prong.

http://www.codecheck.com/250_50_commentary.html

A self grounding receptacle has a special clip on the yoke and will look like this:


They don't require a pigtail ground wire be installed to the metal box. But, like said above, you are not allowed to install a 3 prong receptacle in place of a 2 prong unless the box is grounded. Your existing 2 prong receptacles are fine to use unless you want to run a device that requires a ground, such as a computer.

[jtfoxman]

Thanks for the quick reply!

[jtfoxman]

Well I went ahead and tested the outlets. I get a constant 120v when I touch the black wire and the box. So I am going to go ahead and purchase the self-grounding outlets. I was surprised that the boxes were grounded since I don't see any metal wire cables in my basement or behind the outlets. They wire just looks like the older cable that has a cloth like outer cover.

[kactuskid]

Hmmm, you need to hold off installing those 3 prong receptacles until this can be figured out. If you have the older cloth romex with no ground wire, then you may not really have a ground. But wierd that you would read the voltage then.

Are there any other wires in this box that are connected to the box or making contact with it? Did you disconnect the wires from the receptacle, spread them apart and then take your reading? If you just measured from the front of the receptacle to the box, then it's possible that you may have a bootleg ground somewhere in that box or on the circuit. This is where a ground and the neutral are bonded together on the load side of your electrical service panel and it is very dangerous and can give a false reading of having a ground.

One way to know for sure if you have a bootleg ground is to connect a GFCI receptacle to the wires in the box. The GFCI will sense a ground fault and will trip if anythings plugged into it.

[HayZee518]

What you are seeing in the box is the jute fiber that surrounds the conductors "inside" the bx covering. Newer Bx used a paper wrap instead of the fiber. The jute fiber has a waxy feel to it when you strip off a length of the armor.

[HayZee518]

New Bx - Old Bx

Here's what the old vs the new Bx looks like. In the jute fiber type there may be a blue or red thread along with the tannish jute fiber.

[kactuskid]

Aaah, I'm betting Hazy is right on. You won't see the armored cable from inside the box, only the old wires sticking out of it. When you said you couldn't see it behind the outlets I figured you had access to see the connection from an open cavity in the wall.

And older homes didn't have the wiring run through the basement. It was always run up through the attic and down into the wall studs to the receptalces, usually from the light fixtures which served as the junction boxs.

Course if these receptacles are supplied via Knob and Tube wires then that's a different story.

[jtfoxman]

I looked into the outlet box again and I could see what is coming into the box. It isn't no bx cable. The wires are wrapped in a paper material and that is covered with black insulation and what looks like then it was covered in silver substance, like paint. No other wires in the box.
I checked the main breaker then and there is no bx cable running from that either. I took the cover off and it looked like there was a few connections that had the ground and the white wire together. Is this what you called bonding. Can I just kill the power and unbond them and place the ground in another open spot? Can I put 2 grounds in the same open slot?

[kactuskid]

Neutrals and grounds are supposed to be together in the main panel, they connect to the same neutral/ground buss bar. The rule is one neutral wire per hole. Ground wires can usually be double up in one hole. But this is the ONLY place that they can be tied together.

So, it sounds like you have the early version of romex wire on this circuit or knob and tube, which has no ground wire included in the cable jacket. K&T used the paper insulator and is cloth covered. I can't figure why you are seeing a voltage reading when measuring from hot to the metal box with this type of cable installed. This asphalt covered older romex with the silver covering and K&T wiring has a reputation for becomming very brittle overtime and the insulation flakes and falls off. I'm thinking that it's possible the insulation has broken off the neutral wire where it attaches to this metal box and the bare wire is making contact with this box. This would be very dangerous cause the box is actually live then.

[Snoonyb]

I took the cover off and it looked like there was a few connections that had the ground and the white wire together. Is this what you called bonding.

Yes. For that time period was an acceptable method.

Can I just kill the power and unbond them and place the ground in another open spot? Can I put 2 grounds in the same open slot?

If it isn't broke, do not fix it.
To effectively seperate grounding from the neutral you'll need a seperate bonding buss, which your existing panel may not support.

There may be other reasons for your reading 120V to the metalic box.
It was a common practice to run a bare copper conductor, stapled to the stud face and rather unceremoniously wrapped around a screw where the romex connector attached the romex to the box. There was, and still marginaly used, a friction clip used to attach the bare conductor to the box.

[Phelps]

Does poster jt have a lot of bare ground wires, I wonder, in his panel box? What do those silver wires look like that enter the panel box?: *Are* they just the 2 wires, or is there a ground wire in there with each of them?

And if not, perhaps someone got clever and ran 2-wire, but used an outlet-to-outlet jumper wire system, where they hooked up bare ground wire to the *back* of each metal box (invisible) by either screwing it to the box or by pinching it in the romex wire strain relief?

It seems like that if jt assesses the number of bare ground wires in his panel box and traces each of them back to the top and sides of the panel boxes entry points with the other wires, that he could find out by accountability, if what I am saying just might be possible, if he has some bare copper wires unaccounted for.

[jtfoxman]

I checked the main breaker again and only 3 or 4 of the wires going into the breaker do not have a ground.

So I went back to the outlet boxes and removed the outlet. I seen at the back of the box a little piece of wire so I removed the clamp inside the box that was holding the wires in place. Low and behold wrapped around the insulation of the wires there was a ground that was hidden and was touching the box.

I am thinking when they remodeled the house before we lived in it they didn't feel like unwrapping the ground wire and hooking up a 3 prong so they left it a 2 prong. Every single 2 prong outlet was like this. So I replaced them with 3 prong and I tested them, they all have a ground now. Now only have 3 outlets in the house without a ground and 1 is in each bedroom, these ones there was no ground that I could see. So not a big deal.

I even checked my current 3 prong outlets and a few of them had the ground wires wrapped around each other too. Lazy people just didn't want to unravel the ground wire to hook up the outlets corrctly. It took me awhile at each outlet to unravel the grounds but it was worth it. I even found a plug that was reversed polarized and fixed that to.

Thanks everyone for your input and help on this. You were all a very big help.

[SSN596]

An electrician can deteremine whether it would be proper to install new grounding receptacles. However, on thing you can do which provides a great safety imporvement: you are allowed to replace a 2 prong plug with a GFCI receptacle. This will function to provide personal safety, since if any current finds a path other than back to the neutral wire, the device trips. What this doesn't do is provide the actual grounding conductor which a lot of modern electronic equipment "likes" to have.