Questions about no ground wire

nolan7120 · Jul 25, 2017

I'm going to be doing some tinkering at my mom's house which was built in the 1950's. There are no ground wires or ground bus, but the outlet box in the garage that I'm looking to work on is grounded. I have two main questions:

1) When swapping out a new 3 prong outlet to replace the 2 prong that's there, can I simply use a 12 AWG 8" green pigtail ground wire and connect one end to the green screw on the receptacle and the other end to the inside of the box? The box is grounded and there is no ground screw hole present. I was going to use a 10-32 NF tap after drilling a 5/32 hole in the box to create the ground screw hole. Does this sound correct? Running a new ground wire from the breaker box is not an option.

2) I might hook up a new 110V receptacle on a 20A breaker right outside the main breaker box using metal conduit. I would use 12 AWG wire for this. Should I run the hot, neutral, and a ground wire to the receptacle? I would attach both the neutral and the ground wire to the neutral bus in this case, and just connect the wires straight to the receptacle. Would the ground wire be good with this setup?

OR

Same situation with the new receptacle but this time running only the hot and neutral. I'd be using metal conduit to a metal box housing the receptacle, so I think the box would be grounded. I would use 12 AWG 8" pigtail ground to ground the receptacle to the back of the receptacle box. This is basically the same strategy I'd be using for the garage outlet in question 1.

I am an electrical noob but am confident I can do the job correctly if the process is laid out in a clear fashion. Thanks for any help!

BillK · Jul 25, 2017

nolan7120 said:
There are no ground wires or ground bus, but the outlet box in the garage that I'm looking to work on is grounded.

If there are no ground wires then how is the outlet box grounded ?

nolan7120 · Jul 25, 2017

BillK said:
If there are no ground wires then how is the outlet box grounded ?

You know I'm not exactly sure but I read here (https://www.thisoldhouse.com/ideas/replacing-two-prong-receptacles) that if you take a multi-meter and put one prong in the hot and one prong on the center outlet screw and if you get 120V, then the box is grounded. I did that, and 120V popped up so I'm assuming that it's grounded.

tym · Jul 25, 2017

^ I think you could also get that is somebody just tied the GND and neutral together...

BillK · Jul 25, 2017

nolan7120 said:
You know I'm not exactly sure but I read here (https://www.thisoldhouse.com/ideas/replacing-two-prong-receptacles) that if you take a multi-meter and put one prong in the hot and one prong on the center outlet screw and if you get 120V, then the box is grounded. I did that, and 120V popped up so I'm assuming that it's grounded.

That is not necessarily true depending on how someone has wired things in the breaker/fuse box. They may have used the neutral as a "ground" You really need to do some more research and maybe post some pictures of the outlet box and the breaker box.

KenC · Jul 25, 2017

Chi? how long has EMT been required there? If you have EMT, it is likely the ground path.

The Cobbler · Jul 25, 2017

here, when there are no grounds present it is acceptable to install GFCI outlets at the first outlet and put grounded receptacles downstream of it .

nolan7120 · Jul 25, 2017

I do have a pic of the outlet and breaker box but they're not very good quality. I'll post them in a moment. I'll get some better pics when I go there in an hour and also post those.

American Locomotive · Jul 25, 2017

nolan7120 said:
You know I'm not exactly sure but I read here (https://www.thisoldhouse.com/ideas/replacing-two-prong-receptacles) that if you take a multi-meter and put one prong in the hot and one prong on the center outlet screw and if you get 120V, then the box is grounded. I did that, and 120V popped up so I'm assuming that it's grounded.

The only thing that means is that the ground terminal is hooked up to something. Not necessarily ground. It's even conceivable that if the wood of your house had enough moisture, you might get a voltage reading between hot and the box itself.

nolan7120 · Jul 25, 2017

KenC said:
Chi? how long has EMT been required there? If you have EMT, it is likely the ground path.

I'm not sure but I'm pretty sure EMT is what is used.

nolan7120 · Jul 25, 2017

Sorry about the quality but it's all I have at the moment. The receptacle is a light switch and outlet combo. The light is not needed so I'd just use a wire nut to separate those off.

Bert_ · Jul 25, 2017

The multiple colors in the box and the emt in the basement would lead us to believe that it is piped the whole way. In that case there is not a ground "wire" but the conduit is a perfectly fine ground, so yes put a ground pigtail to the box. That is perfectly fine and legal to wire a new building that way today.

As a bit of a side note, if you need an additional circuit you can pull more/new wires in the current conduit without making any holes in the wall. You might have to open up several outlets to get to the breaker box.

Hot Rod Grampa · Jul 25, 2017

Some early houses after knob and tube were wired with bx. The metallic cover was the ground path. Check to see if you have good ground path to main box with ohm meter. There used to be available box clips that slid over the side of the box holding the ground wire. Were green. Might eliminate the drilling and tapping. If you run new conduit then by all means run an insulated ground as per code. Just thinking out loud.

dscheidt · Jul 25, 2017

KenC said:
Chi? how long has EMT been required there? If you have EMT, it is likely the ground path.

EMT has never been required. You can, if you like, do your house in rigid conduit.

the less sassy answer:
Conduit has been required approximately forever. The original electric conduits in my house were done in rigid, because EMT hadn't been invented yet. (EMT was invented in the late 20's, and didn't become widely used until the late 30s.)

dscheidt · Jul 25, 2017

The easy option is to buy and install 'self-grounding' outlets. They have a copper or brass clip at one of the screws that hold the outlet to the box. the clip bonds the body of the outlet to the box. Since the box is grounded, the outlet is as well. They're generally acceptable when the outlet is covered by a normal cover plate, or installed in an exposed work cover that has recessed corners, and you use acceptable locking screws and nuts (supplied with suitable covers). In other words, places where you have to work to get the outlet free of the box and its ground.

alfredeneuman · Jul 25, 2017

nolan7120 said:
I'm going to be doing some tinkering at my mom's house which was built in the 1950's.

Either the house wasn't built in the 1950's or the panel's been replaced later.

That breaker type (Cutler Hammer type CH) wasn't produced until 1962, and only became popular post-1969 or so.

nolan7120 · Jul 25, 2017

alfredeneuman said:
Either the house wasn't built in the 1950's or the panel's been replaced later.

That breaker type (Cutler Hammer type CH) wasn't produced until 1962, and only became popular post-1969 or so.

Redfin says the house was built in 1955. My parents bought it in the early 70's. Maybe the panel was replaced was between those two time frames.

nolan7120 · Jul 25, 2017

Here's some better pictures:

nolan7120 · Jul 25, 2017

The thick neutral wire near the top of the bus in the 1st and 2nd pic ends up going to a ground on the water line as seen in picture 3.

I'm curious if the box is grounded by the flat-head screw in the 2nd pic. To the left of the neutral bus, there are the two phillips head mounting screws. Above and and below those, there are two holes, one of which is filled in by the flat-head screw. Is this how the box is grounded? Thanks

dscheidt · Jul 25, 2017

nolan7120 said:
The thick neutral wire near the top of the bus in the 1st and 2nd pic ends up going to a ground on the water line as seen in picture 3.

Just because the wire is white doesn't mean it's a neutral. Electrons don't know what color the insulation is. If it's going to a water pipe, it's a ground. I hope that's on the city's side of the water meter, because if it's not, it's not grounded. You should consider running a wire to ground rods outside, if that's the only system ground.

nolan7120 said:
I'm curious if the box is grounded by the flat-head screw in the 2nd pic. To the left of the neutral bus, there are the two phillips head mounting screws. Above and and below those, there are two holes, one of which is filled in by the flat-head screw. Is this how the box is grounded? Thanks

There should be a screw that connects the buss bar to the can. The top and bottom slotted screws hold the plastic carrier to the can. The phillips screw may serve that purpose, I can't tell.

alfredeneuman · Jul 26, 2017

dscheidt said:
I hope that's on the city's side of the water meter, because if it's not, it's not grounded.

If the water service is PVC or poly that's true, but if it's metallic....then:

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more

theoldwizard1 · Jul 26, 2017

The BEST way to protect a circuit/outlet with no ground wire is a GFCI ! It is actually recommended and code correct as long as the outlet(s) are labeled as having no ground. This is great for older home where your refrigerator/microwave/electronics have a 3 prong plug.

Jess · Jul 26, 2017

In my area, the common fix when uodating is to put in GFCI outlets and attach the 'No Ground' label. When I recently had a rental updated, the City electrical inspector advised to place a box with a blank front GFCI next to the panel for the circuits in question and place a new cable from the panel to the box then swing the original cable to the GFCI. We did this to eliminate having to replace all the outlets or change breakers. The only upgrade that we had to do was the kitchen counter outlets. We dodged the AFCI this time...

teamextreme · Jul 26, 2017

Bert already gave you the answer you're looking for, everything else is noise. You have pipe and wire install. The conduit acts as a ground. Confirm there actually is ground continuity by measuring voltage from hot to the box. If you get a voltage reading by using the box as ground, then use a pigtail to the box with a normal grounded outlet and be done. No need for GFI's, or discussion of grounds in Romex, etc.

nolan7120 · Jul 26, 2017

teamextreme said:
Bert already gave you the answer you're looking for, everything else is noise. You have pipe and wire install. The conduit acts as a ground. Confirm there actually is ground continuity by measuring voltage from hot to the box. If you get a voltage reading by using the box as ground, then use a pigtail to the box with a normal grounded outlet and be done. No need for GFI's, or discussion of grounds in Romex, etc.

Thank you for the confirmation. I'm getting a voltage reading of 136 everywhere I've checked, which includes 3 separate outlets (garage, outlet attached to the breaker box, dryer outlet) and several circuits on the breaker box. Is is normal for it to be a little high?

TractorJeff · Jul 26, 2017

nolan7120 said:
Thank you for the confirmation. I'm getting a voltage reading of 136 everywhere I've checked, which includes 3 separate outlets (garage, outlet attached to the breaker box, dryer outlet) and several circuits on the breaker box. Is is normal for it to be a little high?

Check the black incoming wires against the white incoming wire to validate your meter reading of 136. If you get that from BOTH black wires to the white wire, then its OK.

ex: If you told us that one measures 136 and the other measures 104, then it can be assumed you have an incoming power issue.
BUT!
If both blacks to white read 136, then it can be assumed that it is a normal value.
Or
You meter is so cheap that it reads 136 when it should read 120?

nolan7120 · Jul 29, 2017

Turned out I was getting faulty readings from using a multimeter that had a low battery. Swapped out the 9V and back to normal at 120. I'm chalking that up to another noob moment.

theoldwizard1 · Jul 29, 2017

Jess said:
In my area, the common fix when uodating is to put in GFCI outlets and attach the 'No Ground' label.

I am pretty certain that NEC "code" !

Questions about no ground wire

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