You can buy "Self Grounding" outlets. They are identical to normal duplex receptacles except the bottom screw passes through a small bonding clip on the yoke. Apparently this and perhaps all your boxes are piped in with metal conduit, which is providing the ground path.

Hope this helps!

Thanks. Its a start. But it also raises some additional questions. What is a small bonding clip on the yoke? By metal conduit, do you mean that the wires are run through the house in what are essentially metal pipes or is it something about the wires themselves?

-Maureen

I looked up metal conduit so I answered that question. I think it is possible that is the case. I think there are pipes in the attic that are not water pipes - that would explain where they came from.

I would agree it sounds like you have self grounding receptacles with grounding through the conduit. I would not consider this to be grounded. While you have a return path back to the panel, you do not know if it can support the amperage needed to trip the breaker in case of a short. You need to run a wire if you want them grounded.

Metal conduit is/was an accepted ground. I had wiring professionally added in a small business 15 yrs ago and there were no ground wires, only conduit. It worked very well because we tripped a breaker on the first day due to loose wires in a mixer that had a motor swapped out by helpers. The main guy was rewiring ovens and failed to check their work. We went from a place with 3phase to another building with single phase.

In addition to conduit, houses built in '60 often used so-called "BX cable". Whether the term "BX" (actually an old brand name) is applied loosely to AC (armored) cable or MC (metal-clad) cable, the flexible metal sheath will provide continuous box-to-box grounding of metal j-boxes so long as proper connectors are used, etc. You could also have a mixture of conduit and AC/MC cable.

Have you looked at your panel and/or j-boxes to see what kind of wires were used for the small (i.e., 15- and 20-amp) circuits? That ought to give you a clue. Metal sheathed? Conduit? Some of both?

Most receptacles will end up "grounded" when they are screwed into a grounded metal box, whether they have yoke clips or not. That's because they're designed to ensure connectivity between yoke and ground prong. In fact, the installation screws provided the usual method of grounding them during the 60s, before ground wire terminals on fixtures started appearing to meet increasingly stringent code requirements for bonding.

Strictly speaking, though, where a receptacle has a ground post, the ground post should be connected to a grounding wire.

"Most receptacles will end up "grounded" when they are screwed into a grounded metal box, whether they have yoke clips or not."

This is NOT true. The ONLY safe and acceptable method like this IS a self-grounding receptacle with the yoke clip.

If the receptacle is three prong, and not self-grounding, a valid ground wire MUST be attached to the green screw on the device.
This is unless of course it is fed through the load side of a GFI, but that is another discussion.

Thanks everyone. I'm definitely learning more about electricity than I can get out of my "Complete Home Repair Manual." I appreciate everyone's help.

I went to Ace Hardware today and they had never heard of a self-grounding receptacle. Of course, it is Ace Hardware and not an electrical supply store ...

Right now I do not have the time to get the whole house wired with a ground wire (and from what I read, it is recommended that one not simply run a ground wire but actually replace all the wires) ... I have a piece of furniture that is being delivered and the outlets in question will be hidden behind the furniture. I need to have them read to plug in what needs to be plugged in before the furniture blocks the outlet. Right now they are 2 prong outlets and everything that plugs into them (clock radio, bedside lamp, cordless phone) has a 2 prong plug but we thought it would be good to replace the outlets while we still have access to them. What I don't want to to is make them even less safe.

Also, I really don't want to invest in rewiring the whole house if I don't need to ... if the metal conduits are accepted ground, I'd rather invest my house-repair dollars on something else (BTW - we've had some electrical work done on the house ... ran a subpanel to the garage for a complete kitchen remodel, another subpanel to the pool equipment, and brought some questionable wiring up to code and none of the electricians have ever told us we need to rewire or run a ground wire ... which, given they could sell us more work :), I would assume they would tell us). We are going to be replacing the main panel in the next month or two but the furniture is arriving before then.

I am curious about some of the conflict - what makes the box grounded? My understanding of ground is that by connecting the outlet to the ground wire, any excess current gets routed through the grounding wire to earth rather than through the person touching it to earth. My limited (very limited) understanding is that if the metal conduit (which connects to a metal outlet box) acts in the same way as a grounding wire in that it directs the current through the conduit to earth instead of through the person to earth, if the box is directly touching the ground screw and the ground screw is screwed in all the way (so that it is touching the part of the outlet where the ground wire would be touching), isn't that the same as the ground wire touching the outlet? The ground screw isn't insulated so wouldn't the current travel through it from the outlet to the box, to the conduit, to the ground?

terribletom said:

Have you looked at your panel and/or j-boxes to see what kind of wires were used for the small (i.e., 15- and 20-amp) circuits? That ought to give you a clue. Metal sheathed? Conduit? Some of both?

Honestly, I probably wouldn't be able to tell even if I wasn't so intimidated by the panel to not touch it except to turn off a breaker if I have to do work in the house. For me, electrical systems are a little bit like computers - I know just enough to know how little I know! I'm willing to replace lights, switches, and outlets but anything beyond that I get a professional in to take care of it. And, very frankly, I'm darned proud of the little I can do :) I get VERY excited when I make a minor electrical repair and it works! (I confess, I feel the same way about plumbing - although plumbing doesn't intimidate me as much as it intimidates my husband :)

If you can verify that the metal box IS grounded, one of the holes in the back of the box is threaded.

A ground screw can be installed and a pigtail (green or bare wire) the same gauge as the circuit conductors (#14 or #12) installed from the screw to the receptacle.

If you cannot verify the grounding as AC, MC, EMT, or another accepted type using a volt meter to check for ground (or a plug in tester) is not really adequate, though many people do it.

The quality of the ground should be verified with a ground tester to ensure the ground path can carry sufficient current to trip the breaker.

"Most receptacles will end up "grounded" when they are screwed into a grounded metal box, whether they have yoke clips or not."

This is NOT true.

In the context of the OP (where the poster wondered how her outlets could test as grounded and further theorized that the ground screw must therefore be in contact with the box), I submit that the statement is true as written.

We agree (read carefully) that where a receptacle has a ground screw, it should (ok, MUST) be attached to a valid ground wire.

You know what Tom, you're right. I didn't read it that way but I see what you mean.

Thanks everyone for your help.

What are the risks of replacing the existing 2 prong outlet with a 3 prong outlet under these circumstances (i.e., with some, but quite possibly inadequate, grounding)? Does doing so actually create an additional risk (besides making people incorrectly believe that the outlet they are using is grounded)? If a two prong, ungrounded outlet carries a certain amount of risk, does a partially grounded three prong outlet carry GREATER risk than the two prong outlet or is it merely that the risk is not eliminated as it is with most 3 prong outlets? If there is a greater risk, I can always leave the 2 prong plugs in since I don't have any 3 prong devices that plug into those outlets.

Just leave the 2 prong receptacles in place unless you can either be sure of an adequate ground, or use a GFCI receptacle to protect the new 3 prong receptacles.

Every GFCI receptacle cones with stickers for "GFCI protected" for down stream receptales, and "No equipment ground" for 3 prong receptacles protected by a GFCI upstream.

Note that things that need a ground to work completely like plug in surge protectors will provide only limited (line-to-line) protection without a ground.
If the voltage on both hot and neutral rise (called common mode) the surge protector will provide NO protection.

Short of bringing in an electrician to check, is there any way I can test if the house is adequately grounded?

What do you mean by "adequately grounded"?

What I mean by "adequately grounded" is good enough - to paraphrase chris8796,

How can I test if I have a return path back to the panel that can support the amperage needed to trip the breaker in case of a short.

brickeyee said

The quality of the ground should be verified with a ground tester to ensure the ground path can carry sufficient current to trip the breaker.

What is a ground tester? Is it something I can get and can actually be used by someone who doesn't really have any electrical training?

"The quality of the ground should be verified with a ground tester to ensure the ground path can carry sufficient current to trip the breaker.

What is a ground tester? Is it something I can get and can actually be used by someone who doesn't really have any electrical training? "

Absolutely not. Even many electricians are not equipped to effectively test this.
It is more a visual check than anything.

"The quality of the ground should be verified with a ground tester to ensure the ground path can carry sufficient current to trip the breaker.

What is a ground tester? Is it something I can get and can actually be used by someone who doesn't really have any electrical training? "

Absolutely not. Even many electricians are not equipped to effectively test this.
It is more a visual check than anything."

The first thing to do is visually check for the presence of a grounding conductor, or the use of AC, MC, or metal conduit.

1960 is old enough that NM (non-metallic) sheathed cable was in use, but the grounding (bare or green) conductor was no uniformly required.
Initially grounding conductors even were allowed to use a smaller gauge of wire (around #18 solid).

Thee grounding conductors can sometimes be found wrapped around cable clamps on the outside of boxes.
Some folks had no idea what to do with them.

AC (armor clad/cased) provides grounding through the metal armor and a thin bonding strip n side the cable.
You will notice AC cable clamps have a set screw and make a solid connection to the armor.
MC cable normally has a run ground wire since the bonding strip is not present.
Metal conduit can also provide a grounding path.

If you want to test for grounds at least use a 60 watt light bulb and a pair of leads.
If the bulb lights brightly between hot and ground the ground is carrying 0.5 amps.
A meter or receptacle tester is only using a few milliamps of current.

Larger electrician shops that do commercial work may have a bond tester that can be used to verify grounding connections.
They cost a few thousand dollars and see use in larger structures to verify that the ground in some remote corner of a building is still adequate.

There are ways to rig up suitable loads to check ground capacity, and I had a setup like that before purchasing a full up bond tester.

It has also seen use in checking lightning damaged electrical installations along with a megger and a TDR (Time Domain Reflectometer, radar on a wire) to find insulation damage and cable breaks.

Wow - this stuff is WAY beyond me. It looks like we have to replace our panel altogether so we'll find out then what's up. In the meantime, I guess I'll leave the 2 prong outlets in place and keep using adapters.

So, I took out one of the outlets again to take a look and discovered that there is a copper wire that comes into the box from the wall and is attached to the back of the box (this is in addition to the negative and positive wires). Perhaps that is the ground?

"So, I took out one of the outlets again to take a look and discovered that there is a copper wire that comes into the box from the wall and is attached to the back of the box (this is in addition to the negative and positive wires). Perhaps that is the ground?"

That would be a ground.
They are allowed to be bare, green, of green with yellow stripes.

Disconnect it from the box, pigtail it with two free wires.
One wire goes back on the box screw, the other connects to the green screw on the receptacle.

Thanks brickeyee!

I do think it is odd that they took the trouble to add a ground wire (it does look like an after the fact thing) and didn't put 3 prong outlets in.