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#63802 - 03/25/06 07:00 PM ground screws
circuit man Offline
Member

Registered: 11/05/01
Posts: 287
Loc: saluda,s.c.
here is one i have been wondering about & have no idea.why do outlets not have two green screws for the bare grounding wire? i know this sounds crazy but this has had me puzzled all day.they have two screws for the neutral & hot , bu not ground.

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#63803 - 03/25/06 07:29 PM Re: ground screws
Lostazhell Offline
Member

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
I have a few Sierra outlets that have the twin ground screws, but I'm guessing the idea of mounting a bare ground wire on the same side as the hot could lead to some interesting experiences if you're not careful...

Could also be something to do with current listing requirements

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#63804 - 03/25/06 07:34 PM Re: ground screws
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
I would assume it is so you are not depepnding on the device as the fault clearing path. If you were to take out the device, you would have no path for fault current until you connected the two EGCs together. Sort of the same concept as 300.13(B) for the grounded conductor of multiwire circuits.
_________________________
Ryan Jackson,
Salt Lake City

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#63805 - 03/25/06 07:39 PM Re: ground screws
Radar Offline
Member

Registered: 04/30/04
Posts: 349
Loc: Los Angeles, CA
Frankly, I wish they only had one connection each for the hot & neutral also, making it impossible to depend on the device for circuit continuity.

Radar
_________________________
There are 10 types of people. Those who know binary, and those who don't.

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#63806 - 03/25/06 09:06 PM Re: ground screws
Sixer Offline
Member

Registered: 08/08/05
Posts: 264
Loc: Canada
2 hot and 2 neutral screws allows you to have a duplex receptacle with 2 separate circuits that don't share a neutral, using a 4-wire feed.

Ryan J has got it: 2 ground screws would allow for non-pigtailed grounds. If the receptacle was ever removed, the ground would be interrupted to devices "downstream".
_________________________
Sixer

"Will it be cheaper if I drill the holes for you?"

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#63807 - 03/26/06 02:50 AM Re: ground screws
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
I agree with Ryan and Sixer that having and using two ground screws on devices would lead to 250.148 violations.

250.148 in part
 Quote:
The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire (fixture), or other device fed from the box will not interfere with or interrupt the grounding continuity.


 Quote:
Frankly, I wish they only had one connection each for the hot & neutral also, making it impossible to depend on the device for circuit continuity.


I can not agree with that.

You are free to pigtail the device if you want but assuming proper installation it is not unsafe to feed through a device.

Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#63808 - 03/26/06 10:27 AM Re: ground screws
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
It's amazing the assumptionf different folks make. These assumptions may never even be reflected in, or inferred to by, standards and codes....but they are there nonetheless.

Having dealt with some folks in the design and testing of receptacles....they, like most real electricians, assume that only a DIY will actually connect two set of wire to a device- surely not more than that! It is also recognised that it is a fairly common trade practice to "split" a receptacle. (Switched receptacles for lighting and the dishwasher/disposal receptacle are prime examples of this).

And, unless you're a HIY or tract hacker, you use a pigtail.

Another assumption these days is that you'll be using a "greenie" to join the grounds together.

Until recently, it was quite possible to legally wire a receptacle without connecting the ground wire directly to it; a connection to the metal box was considered sufficient. Even today, I think it is assumed that the primary connection will be to the box, with a eparate pigtail to the receptacle.

Receptacles probably would have been made completelt without a ground screw, except that, in plastic boxes, you really need to attach that wire to something! I'm certain this is the real reason switches have ground screws....speculation about metal cover plates notwithstanding!

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#63809 - 03/26/06 04:24 PM Re: ground screws
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
"or tract hacker"...

Careful, you are talking about every 1&2 family electrician out there who wants to win a bid. Most I see "stab". Until U/L and NFPA say it is wrong, AHJs accept it.
_________________________
Greg Fretwell

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#63810 - 03/26/06 05:26 PM Re: ground screws
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Right, G, its' legal. At least, for up to two wires per side. More than that, and it's debatable.

But you assumption that the guys who do this might consider being called a "tract hacker" an insult may not be correct. These guys seem to take pride in just how fast, and cheaply, they can wire a house to the most minimum standard...I can even think of one member of this site who calls himself "Romex Racer." For all I know, 'track hack' might be the next rung of their professional ladder! :-)

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#63811 - 03/27/06 01:40 PM Re: ground screws
winnie Offline
Member

Registered: 09/15/03
Posts: 652
Loc: boston, ma
When differentiating between two installation methods, both of which meet code, and both of which have been listed by a suitable testing lab, qualifying one as a 'hack' and the other as 'good workmanship' is at best a gut feeling supplemented by experience and anecdote.

'We all know that backstabs are bad.' Seems to me that well controlled spring tension in a device would do a better job of making a splice than a randomly tightened screw. At the same time I would never use a backstab.

Connecting two sets of wires to a device. When working with stranded wire and commercial 'back wire' receptacles, my _gut_ feeling is that the screw and pressure plate of the receptacle would make a better splice than a wire-nut. Barring multi-wire circuits, I will by preference connect multiple pairs of wires to such a receptacle.

-Jon

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