[RE-wrenches] Stainless steel, self-tapping grounding screws

[August Goers]

Hi All -

Note that there is a difference between self tapping and thread forming screws. Self tapping screws are not a good choice for bonding. In my opinion, thread forming screws are also a marginal choice unless used with a nut and star washer on the back side. All it takes is just a little bit of overtightening and the soft aluminum module frame will strip out when using thread forming screws. Sure, any good experienced installer has the right touch to tighten the screws just right but newer members of the crew will surely strip threads from time to time. If you use a kep nut (such as McMaster PN: 96278A411</#item/96278A411>) on the back side of the frame you'll be sure you have a sturdy bond. Once you try the kep nuts you'll never want to go back to just plain screws because you can go good and snug and never worry abour stripping the aluminum...

See some of you folks down at the Solar Power conference! Best, August


August Goers


Luminalt Energy Corporation
O: 415.564.7652
M: 415.559.1525
F: 650.244.9167
www.luminalt.com<http://www.luminalt.com/>
________________________________
From: re-wrenches-bounces at lists.re-wrenches.org [re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mick Abraham [mick at abrahamsolar.com]
Sent: Saturday, October 24, 2009 6:36 AM
To: RE-wrenches
Cc: Rick Turley
Subject: Re: [RE-wrenches] Stainless steel, self-tapping grounding screws

Nick didn't specify screw diameter, but assuming #10-32:

Try #96024A310 from McMaster-Carr (www.mcmaster.com<http://www.mcmaster.com>) These cut threads into aluminum pretty well.

I also use stainless "external star" washers for the ground lug task: #98438A230, same source. One washer between lug and solar module frame bites into both surfaces.

The above mentioned screws require a 5/32" pilot hole. If your modules don't already have that you'll need to protect the Tedlar back sheet with a scrap of wood then drill through the aluminum flange. This operation is possibly non-code, possibly non-acceptable to your authority having jurisdiction, and possibly a reason for the module manufacturer to disallow warranty on the drilled modules. Drama, drama, drama.

A 5/16" hex bit is required to drive the thread cutter screws and I find this cannot be done by hand. A cordless drill works but be careful to not strip out the aluminum threads you're cutting. Get them tight...but not too tight.

Side Note: The same screws do not tap well into the thin NEMA 1/NEMA 3R steel pulling boxes. The cutting teeth seem to grind away before they get a good bite in the steel.

Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com<http://www.abrahamsolar.com>

Voice: 970-731-4675


On Fri, Oct 23, 2009 at 6:17 PM, Nick Soleil <nicksoleilsolar at yahoo.com<mailto:nicksoleilsolar at yahoo.com>> wrote:
Hi wrenches:
    I am looking for a new source for stainless steel, self-tapping, 32 thread per inch screws to bond Ilsco lugs to module frames.  I used to buy these from Fastenal, but they don't supply them anymore.  I have been using WEEB lugs, but one city jurisdiction doesn't allow them without the letter of authorization from BP Solar.  I have contacted BP a couple times, requesting that they provide a letter to WEEB, and I heard, "it's complicated."  I guess so.
    Maybe I will bolt the Ilsco lug through a threaded hole.
 Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell: 707-321-2937
Office: 707-789-9537
Fax: 707-769-9037



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