FW: Grounding screw requirement [RE-wrenches]

Joe Felker joe.felker at alumni.stevens-tech.edu
Thu Feb 21 03:55:43 PST 2008


Aaron,
Look in 250.8 Connection of Grounding & Bonding Equipment
It permits the use of machine screws or thread-forming screws that 
engage not less than two threads

Joe

Aaron Wellendorf wrote:
> 
> 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



Joe Felker

Engineering Manager
NABCEP Certified Solar PV Installer
The Solar Center


- - - -
Hosted by Home Power magazine

To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at re-wrenches.org

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------




More information about the RE-wrenches mailing list