Phil Munro wrote:
Takoma Park Volunteer Fire Department Postmaster wrote:

Phil Munro wrote:

Takoma Park Volunteer Fire Department Postmaster wrote:

blueman wrote:

When used with metal boxes, do the self-grounding outlets provide as
good a quality result as using a separate screwed-in grounding wire?


According to underwriters laboratories the answer is yes.
--
Tom H


It should be noted that the "screw ground" will not be a good one
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 pulling
against the screw to the box. --Phil

That simply is not true. If the receptacle is installed in accordance
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


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
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