FW: Grounding screw requirement [RE-wrenches]

[Aaron Wellendorf]

Fellow wrenches,

I am resending this as it did not seem to post.

I am trying to come up with documentation regarding the requirements for
ground screws, such as those used to mount a mechanical lug inside of a
disconnect switch or a junction box. I have seen installations with a
Tek screw holding ground lugs to electrical boxes. I have always
used/required the typical 10-32 ground screw that is self tapping, or a
properly sized pre-threaded hole to put in the 10-32 screw. I was taught
that proper thread engagement was 3 threads touching the metal to ensure
long term contact and continuity. I am searching for the requirement for
the 3 threads or any other specification relevant. I have searched my
electronic copy of the NEC and can't find a reference to this. Can
anyone tell me where a written specification can be found?

Square D tech support says that to maintain their UL listings, their
safety switches require the use of their grounding kit, part #GTK0610,
which has a 12-24 hex head self-tapping screw 0.62" long with a washer.
The screw must be installed in the location marked with the ground
symbol. 

	"Aaron,   All of our  safety switches have a UL label inside the
switch that lists the UL listed accessories that can be used.  The
ground kits for these switches are listed on this label.
These UL listed kits are the only accessories that should be used in
these switches to retain the UL listing, and warranty.  Using anything
not listed on this label will not be UL listed as an accessory, and void
any warranty.
	Tim Milbert  Product Support Specialist"

Thank you,

Aaron Wellendorf


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