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cre10 12-01-2012 01:00 PM

Grounding With Metal Boxes
 
How do you guys do your ground? I've seen this a few times with metal boxes. They say you can ground on the wire nuts like that and then when the metal outlet tabs and screws are screwed into the metal box that it grounds itself without using the ground screw on the outlet and in the box. What are the pros/cons of this?

http://i648.photobucket.com/albums/u...201_102638.jpg

padraic 12-01-2012 01:04 PM

In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.

mterry 12-01-2012 01:04 PM

Doesn't seem like the most secure connection for a ground. Should make a pigtail from the box, pigtail to outlet ground screw, and connect those to incoming ground(s)

cre10 12-01-2012 01:11 PM

Quote:

Originally Posted by padraic (Post 1064268)
In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.

Wouldn't it melt and cause a fire either way if the ground became hot?

stickboy1375 12-01-2012 01:12 PM

Quote:

Originally Posted by cre10 (Post 1064276)
Wouldn't it melt and cause a fire either way if the ground became hot?

it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...

Why people throw out comments at will is beyond me.

cre10 12-01-2012 01:15 PM

Quote:

Originally Posted by stickboy1375 (Post 1064280)
it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...

Why people throw out comments at will is beyond me.

So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?

stickboy1375 12-01-2012 01:15 PM

The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.

stickboy1375 12-01-2012 01:16 PM

Quote:

Originally Posted by cre10 (Post 1064282)
So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?

its far from okay, fix the issue.

cre10 12-01-2012 01:17 PM

Quote:

Originally Posted by stickboy1375 (Post 1064283)
The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.

How long ago was that technique used?

stickboy1375 12-01-2012 01:18 PM

Quote:

Originally Posted by cre10 (Post 1064287)
How long ago was that technique used?

A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.

Jim Port 12-01-2012 01:20 PM

Probably 40 years ago or more.

The sheath must extend into the box at least 1/4". All grounds need to be connected together and to the box and device.

Anti-wingnut 12-01-2012 02:13 PM

Quote:

Originally Posted by cre10 (Post 1064282)
So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?

It is an incredibly sloppy application, there is no way that it is OK.

Daniel Holzman 12-01-2012 03:21 PM

Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.

Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.

stickboy1375 12-01-2012 03:25 PM

Quote:

Originally Posted by Daniel Holzman (Post 1064374)
Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.

Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.

It's a hacked installation, and the yellow NM shows it's not an old installation. And ground screw does not have to be green.

rjniles 12-01-2012 03:32 PM

Quote:

Originally Posted by stickboy1375 (Post 1064290)
A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.

It was done back in the 50's through the 60's (when grounded cables became a requirement), primarily in the Northeast. And hence the name "Boston Back wrap". But even then the sheathe was brought into the box and the ground was wrapped tightly back around the cable and secured under the clamp. Even if done correctly it is no longer compliant.


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