This is existing wiring from the mid 60s on all the outlet boxes and all outlet boxes have a ground wire attached to the metal outlet box and they were originally 2 prong outlets and I want to convert to 3 prong do I need to use another ground wire and attach to metal box and green screw on the receptacle or is the 3 prong automatically ground by being attached to the grounded metal box. I also used the 3 prong tester that said it was grounded I assume they work. Thanks

I know the feeling. What I have found is that the metal boxes lack the tapped grounding holes in the bottom of the box. If you have them, the process is easier.

I'll assume you don't.

Take a look here:

IDEAL INDUSTRIES, INC. - Grounding (http://www.idealindustries.com/products/wire_termination/grounding/)

There are two items in particular that are useful. First the Term-a-nut (green) and the grounding clips.

I've also used the ground screw things with a solid wire attached and cut off the screw. A piece of solid green wire will also do.

The best solution, I've found is to CAREFULLY unwrap the ground. The ground tended to be attached to the Romex strain reliefs and not a ground screw. There wasn't any.

Once the ground wire is exposed and positioned, you want to add a ground clip to the side of the box with a piece of 14 or 12 AWG solid wire. The other end will connect to the Term-A-NUT.

Now you will have a fork terminal to attach to the outlet with stranded wire. And the box will be grounded.

A connection via the attaching screw to the box on the outlet is not a valid ground.

The Term-A-Nut is available at electrical supply houses. The grounding clips and small solid pigtails at your local hardware store.

That seems to be the easiest way.

The easiest way is to use self grounding recpts. These have a metal clip on the screw that assures the continuity of the ground.
https://lightsonrus.com/store/products/Leviton-15A-Self%252dGrounding-Duplex-Receptacle-%252d-White.html#
All the manufacturers offer them.

You wouldn't do that, if you discovered that a major manufacturer's outlets were defective internally due to a friction ground and because of it did many thousands of dollars damage to equipment. Over 420 outlets in one building had to be replaced.

In residential, there are always problems with paneling and box extenders etc. I wouldn't trust that method with a 10' pole. Just me.

Been burned.

Keep- Could you fill me in on the defective recpts? I've used hundreds of these and would like to know what happened. Thanks in advance.

It's not the type in question, but I can fill you in:

About 20 years ago a major recept manufacturer created a receptacle that when two three prong plugs were inserted in one of the defective ones, the ground would lift.

This created havoc with computers back then. PC's didn't exist, but micro computers did. Fried it big time because the switching power supplies used in the computer raised the ground potential of other serial devices by about 60 VAC. It let out the magic smoke.

I discovered this when using an outlet tester that would measure the ground reistance and I put in another plug and wiggled. The grd connection would break only if two plugs were used and one was wiggled.

The ground bar within the outlet was asymetrical and brass. It made a mechanical contact to the mounting bar with a single point contact. You could see the arcs between them when the outlet was taken apart.

It was really due to the tolerences on the way the body was moulded whether the outlets would have the problem. It wasn't safe to keep them in a laboratory setting where equipment costs sometimes up to $1M+ dollars. e.g. Scanning Electron Microscope. The grounds mattered.

I don't see what this has to do with a currently produced self grounding recpt. These are good reliable devices and I use them with no hesistancy.

It uses a mechanical clip, right?

They won't don't work, for instance, when paneling is placed on top of sheetrock and they won't work well with some ceramic tile installations?

I don't trust mechanical friction connections. Period.

These recpts work just fine over paneling and ceramic tile. Never had a problem and trust them. You are entitled to your opinion, of course.

"Self grounding" receptacles are rated to work with the ears tightened on the outer finish material.

However, I do not think that "Self grounding" receptacles should be discussed or recommended to DIY'ers, as there are variables to deal with, and the potential of problems. Should only be installed by qualified electricians.

The rule is to connect a bonding conductor to the green grounding screw of a receptacle. Train and advice DIY'ers to do it the right way, no shortcuts.

You guys have really confused me. As I have stated I have a house in Orange County California that was built in the mid 60s and the house has all metal outlet boxes with ground wire attached with metal clips on the front and they had a two prong outlet. I want to convert to 3 prong. I already installed one outlet with a 3 prong and then used my 3 prong outlet tester and it shows that everything is OK and its showing no open ground. Is this acceptable. Or would it be better to take the clip off and attach wire to the recept. Thanks

Best to, somehow, attach the ground wire to the box and the receptacle. If you can provide a picture of what you have , we can tell you exactly what to do.

Sorry, but us tradesmen end up discussing the various methods, materials, products, codes, etc. and end up doing just what we don't want to do, make a complicated trade even more complicated. None right and wrong, just different.

There is discussion of receptacles that are available that don't need the ground wire attached. However, there are issues to be concerned with, and my advice is to go back to the basic rule of code, ground it with a wire.

What you ended up with is options. There are rules, and exceptions to rules, in this case simply because of a certain product out there called "self grounding" devices.

My advice to anyone, esp to DIY'ers, is follow the rule, and there won't be any issues. Exceptions can sometimes be more difficult to get right, due to so many variables.. My advice is foolproof.Certain exceptions are really best done by electricians, they will see any problem conditon right off, and work around it.

Kiss gave some products that will do the job.

Nice job tk:

I'll add the following.

Fault currents are best handled by a wire to the receptacle. Then the box has to be grounded with a wire too.

So, you have to look at options. With the box there are two possible ways:
1. a ground clip
2. use a ground screw
3. An empty clamp screw

Some of these options will not be available, so you have to pick one.

The ground clip works all the time, but they are a pain to install.

The Term-a-nuts are about $20 for a pkg of 25. The devices are also available as a black, white and grn package.

I recently replaced the receptacles in a condo and used the Term-a-nut gizmos for all. I was EXTREMELY happy with the result. I just accidentally picked up a wire end rather than a fork end. Look for a change in packaging in the future.

The hard part is cramming the extra wirenuts into the box.

I like the fact that your dealing with stranded wire, so the outlets go in easier.

I personally don't like the backstabbed wires and they offer the ability to terminate the neutral away from the outlet. This is a MUCH better way of doing the connections.

The caution is worrying about breaking the existing ground wire. The conversion will go quickly.

I've had good luck with that technique which again is:

1. remove outlet and disconnect.
2. unwrap ground wire carefully
3. cut ground if necessary to accept a term-a-nut
4. run a piece of solid wire from the term-a-nut termination to the side of the box with a ground clip. This is easier said then done.
5. attach green term-a-nut

Optional:
6. Attach White term-a-nut to white wires.
7. Attach black term-a-nut to black wires

8. Now you have 3 stranded wires with fork terminals. Attach to outlet, etc.

There may not be enough room to use the Term-a-nuts when using GFCI's.

It seems to work well.

So, arm yourself with some term-a-nuts, ground clips and outlet spacers (small pieces of lime green plastic) and go for it.

If you have a hole for a ground screw, then pigtails with ground screw to ground screw would be easier. Use a fork terminal on the ground of the outlet to the ground screw. This is by far the easiest.

Here is a pic of the clip and the screw, but I don't like the method. Go to the outlet ground FIRST. Then ground the box.

http://www.tpub.com/content/construction/14026/img/14026_153_2.jpg

Most outlets will have two cables coming in because of the daisy chain.

Basically, the resoning is simple:

1. A fault will take the path of least resistance (go to outlet first)
2. The metal box and outlet must be grounded. (Your not allow to rely on the mounting screws
3. Pigtailing the neutrals is good practice. (It prevents loose neutrals on an outlet failure) Sometimes it's required.
4. Pigtail the hots for the same reason (reliability)

Good luck!

I hope the reasoning makes sense. I'm with tk concerning the use the wires technique.

Just check to see if tapped holes for a ground screw are available, otherwise you'll have to deal with clips.

OK, give your keyboard a chance to cool down. LOL

That's he funniest line I've heard. Thanks. Can't spread the rep.