Self-grounding outlets vs. grounding wire

When used with metal boxes, do the self-grounding outlets provide as good a quality result as using a separate screwed-in grounding wire?
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In My Humble Option:
According to US NEC 250.148(A) the metal box must be connected to the equipment grounding conductor via a grounding screw or listed grounding device.
As for the receptical, after looking, 250.146(B) says you can use the yoke to metal box as a grounding path if designed so.
I'm sure the electrical experts will have comments about this, but I would not want to have to 'settle' ever for an 'implied' ground. I want to see everything connected. Plus, if the receptacle has a grounding screw installed, then 110.3(b) must be followed. Simply put, read the receptacle's manufactures instructions. So use the ground screw.
hth,
tom @ www.URLBee.com
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blueman wrote:

According to underwriters laboratories the answer is yes. -- Tom H
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Takoma Park Volunteer Fire Department Postmaster wrote:

unless the outlet is fastened to the box with metal washers for proper spacing, and then screwed down tightly. I see lots of outlets that are loosely screwed because the metal box is not flush with the finished wall. The wall plate then holds the receptacle in place against pulling against the screw to the box. --Phil
--
Phil Munro Dept of Electrical & Computer Engin
mailto: snipped-for-privacy@cc.ysu.edu Youngstown State University
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Phil Munro wrote:

with the manufacturers instructions no washers are required. Self grounding receptacles are tested for grounding continuity using only the mounting screw that is held captive by the spring on the yoke that assures conductive contact between the yoke and the mounting screw. -- Tom H
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Takoma Park Volunteer Fire Department Postmaster wrote:

Hmmm. Yes, I have seen that spring clip on some new receptacles in the stores. But I have a lot of slightly older receptacles, and see a lot of older ones installed, that do NOT have that clip. And they cannot be screwed tightly against the metal box unless the box is in just the right flush position with respect to the wall surface. This also has a lot to do with the size of the wall hole around the box. Again, construction practice seems (from my limited observations) to get away with holes that are only just barely covered with the plate, and in this case the receptacle tabs may not allow for much tightening of the screw. Of course the clip helps solve the electrical continuity problem. --Phil
--
Phil Munro Dept of Electrical & Computer Engin
mailto: snipped-for-privacy@cc.ysu.edu Youngstown State University
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Phil Munro wrote:

Without that spring the receptacle cannot be listed as self grounding. If you thought I was advocating relying on the mounting screws of ordinary receptacles as the grounding pathway think again. I am only talking about the receptacles that have been tested by an electrical testing laboratory and listed as self grounding. -- Tom H
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blueman wrote:

Much better. No one forgets to connect the self grounding outlets, but many times they don't bother with the wire.
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Joseph Meehan

26 + 6 = 1 It's Irish Math
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No matter how approved it is, if the grounding connection can be moved or compromised by normal mechanical vibration (even kids running down the hall cause such vibrations), then the ground is not sufficient. Approved ground make it virtually impossible for the ground to be compromised by vibration or receptacle movement when the power cord is attached.
Not only do you want 'their' approval. The receptacle must meet 'your' approval. Safety ground must remain fully connected at all times - which is why the #10 screw that hold receptacle to box, alone, is not sufficient as a safety ground.
blueman wrote:

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blueman posted for all of us....

mental state. You are making progress.
Oh, you want a real answer? Do the research Jeffy. But a big clue here is do you think they would be listed by approval agencies if they didn't work? (sorta like your brain)
--
Tekkie

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Assuming the box is grounded, yes. Obviously a plastic box wouldn't work, but even metal boxes may not be grounded properly, so check.
Jeff
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