No threaded hole for grounding wire in outlet box

[ilya]

I live in an older apartment and I would like to replace a 2-prong receptacle in one of the outlets with a grounded 3-prong receptacle. The outlet box is grounded via armored BX cable (after connecting a multimeter between the outlet box and the hot cable I see 120V).

The problem is that the outlet box does not have a threaded hole for attaching a grounding wire. What is a code-compliant way of grounding the receptacle in such case? Is it possible to drill and tap a hole for the grounding screw?

Thanks!

 

[bassman]

You can use a grounding clip instead of a ground screw, or drill and tap a 10-32 hole for a gr scr, but easiest thing to do is use a self grounding outlet, thoung I would first check to verify 120v. to the box to make shure the box is actually grounded. In old buildings, things have a way of getting screwed up over the yrs

 

[pentavolvo]

if its a metal box just screw the outlet to the box it will ground through the mounting holes

 

[kert]

Be aware that not all BX armor is rated for grounding. Steel is not as good a conductor as Al or Cu, and the coils do not necessarily make contact, so you can have what essentially ammounts to a heating coil.

To be rated for grounding, the BX needs to either have a separate ground wire or a bonding strip within the jacket.

If it were me, I would probably install a GFCI and not worry about it. GFCI will trip in the event of a short to ground (on the recepticle side).

 

[jbberns]

Use gfci. I wouldn't use armored cable as a ground.

 

[bassman]

Bx cable sheeting is rated as ground. A lot of metal boxes are not flush with the wall, so he might need a self grounding Rec.

 

[ilya]

I was going to plug a tv and a home theater to the outlet in question. My understanding is that a GFCI receptacle won't protect the electronics without a ground connection.

 

[BigJohn20]

I was going to plug a tv and a home theater to the outlet in question. My understanding is that a GFCI receptacle won't protect the electronics without a ground connection.

A GFCI isn't for electronics, it's for people.

Standard surge surpressors need a ground to function properly

 

[kert]

Bx cable sheeting is rated as ground. A lot of metal boxes are not flush with the wall, so he might need a self grounding Rec.

That is not true for older BX cable. There needs to be a bonding strip within the cable. Based on the fact that he only has a 2-prong, I'd say there's a good chance his doesn't have a bonding strip.

 

[sberry]

Are you plugging 2 wire ungrounded equipment in to it?

 

[cderalow]

Are you plugging 2 wire ungrounded equipment in to it?

this.

the simplest solution is normally the easiest.

unless the cables are double insulated, chances are your equipment isn't grounded through its cable if it's two pronged.

 

[Charles (in GA)]

Code allows you to install a GFCI in a two wire no ground system, just label the receptacle "no ground". It will work perfectly fine and not cause any problems.

A GFCI looks at current coming in vs current going out (neutral to hot) and if they differ (leakage to a ground such as a hair dryer falling in the tub) then it trips. It does not need nor use the ground for anything to do with the GFCI function.

Charles

 

[Mattlt]

You said apartment. Shouldn't this be the landlord's problem?

 

[nehog]

If you are installing a surge protector (not a GFCI, as pointed out above) then the ground needs to be there, and needs to be a very good ground as well... The 'quality' of the ground is what will determine whether the surge protector actually protects anything or not.

I'd recommend you install a new outlet from the breaker box if you own the property, and if you are renting/leasing then have the landlord install it.

 

[sberry]

I dont think ungroundedequipment will benifit from surge protecion? Its good on a device like computers, grounded case and connected to phone lines where most problems come down.

 

[sberry]

I was going to plug a tv and a home theater to the outlet in question. My understanding is that a GFCI receptacle won't protect the electronics without a ground connection.

If the stuff is 2 wire it wont help adding a ground.

 

[jlckmj]

Just get a self tapping screw, the type with the drill bit on the tip, get it started into the back of the box, wrap the new ground wire around it and drive it home.

Jim

 

[jbberns]

Just get a self tapping screw, the type with the drill bit on the tip, get it started into the back of the box, wrap the new ground wire around it and drive it home.

Jim

Self tapping screws are against code. Has to be a drilled and tapped 10/32 minimum. A GFCI would be the correct install, unless you pull a new cable.

 

[Speedy Petey]

I just want to comment on this thread.
On other message boards I see a LOT of erroneous and even dangerous electrical advice given, especially on non-dedicated electrical boards such as this. I am impressed and glad to see so much correct advice given, and even correcting the mistakes by others.
It is refreshing to see this.

 

[ilya]

Today I finally opened the box with my new television and it had a two-prong plug. For now I'm not going to worry about installing a grounded receptacle in the outlet. Thanks a lot everyone for your advice!

 

[Fred43]

From my experiences all BX wire either had a double steal jacket or the this bare wire we used to back wrap arounf the cable to sit under the clamp and hold the anti-short in place. It was the only method of grounding in the 1930's to the 1980's. Thats when MC cable came into play with a separate insulated ground wire. If the box is flush with the wall surface such as old work, the mounting screws will be adequate. If the box is recessed at all a grounding wire and ground clip is needed. A GFCI will be for shock protection more than a dead short behind the receptical. A wire scraped by the wire clamp will liven the box & receptical yoke without popping the breaker or GFCI if the box is not grounded.