[RE-wrenches] The Demise of WEEB

Mon Sep 13 13:26:03 PDT 2010

Hi There,

This from the Wiley website is an interesting summary.

I am assuming that this is an up to date comment.

========================================================

Brian Teitelbaum (AEE Solar Tech Rep) has authored the following guide to
one of the most debated topics in the industry. I am sure you will find this
explanation of module grounding helpful.

Tech note from Brian Teitelbaum:

lay-in-lugLay-In lugs are sold in ten packs (part number 051-03414), with
the special "thread-forming" screw. That #10-32 "thread-forming screw" that
comes with the lugs in the ten-packs, is a very special screw, and is very
hard to find out there in the world. We had to contract with a screw
manufacturer to get them. They are different than a "thread-cutting" screw,
or a " self-tapping" screw. Both of those type of screws actually cut out
some of the metal from the module frame as they "cut" the threads. This
creates a microscopically loose thread connection that can allow oxygen in
and create corrosion over time. They are not usable for a permanent ground
connection. The "thread-forming" screw actually "folds" the metal, and
"forms" a thread in such a way that there is an oxygen-free junction between
the frame metal and the screw. This produces a better electrical "bond" and
a proper ground connection that will last over time.

This is what the module manufacturers have in the past specified, which is
why we have sold tens of thousands of them over the years.

However. New thinking (mostly from John Wiles who helps to write the solar
section of the Code, and is a stickler for detail) has suggested that the
#10-32 thread-forming screw does not grab enough metal in the module frame
to make a proper ground. Module frames are made from rather thin aluminum,
and even though the 32-thread-per-inch screw has very fine threading, the
module frames are only thick enough for the screw to make contact with only
about two of the screw's threads. Not a whole lot of contact area. Wiley
Electronics, who make the WEEB equipment, has demonstrated with actual tests
that the screw gets very hot and the connection fails when carrying high
current (amps) in a simulated fault condition.

John Wiles now recommends that the lug be connected to the module frame with
stainless steel bolts and nuts, with flat washers and a lock washer that
makes much better contact with the frame. But since frames are anodized, and
the anodizing actually acts as an insulator preventing a good electrical
connection (hence the need for the thread-forming screw to fold the metal,
breaking the anodizing, and creating an oxygen-free connection to prevent
the aluminum from re-oxidizing, which is essentially re-anodizing), Wiles
says that you have to take some Emory Cloth (sandpaper) and scrape off the
anodizing where the lug contacts the frame. Then to prevent oxidation, the
scraped area has to be covered with a (messy) anti-oxidant paste, and the
lug bolted down onto that. Messy, time consuming, ugly, and very hard to do
with any consistency. And it may even violate the module warranty.

I think that using a stainless star washer between the lug and the frame,
would be better, even though Wiles has not given his blessing to that idea.
The star washer bites into the aluminum with a greater amount of contact
than just a couple of screw threads, and is much quicker and more consistent
than sandpaper and paste. We may swap the thread-forming screw out for the
bolted hardware in the future (so much to do..so much to do.)

 <http://www.we-llc.com/WEEB.html> wiley-clipIn my opinion, the WEEB-6.7 lug
is far superior to either method above. It is a wider lug, which has much
more surface area in contact with the module frame (or mounting rail where
it is more commonly attached), which spreads out the heat developed during a
ground short. The stainless steel WEEB washer that comes with the lug has 4
" nubs" that bite into the module or rail metal, and crushes to form an
oxygen-free connection. It is ETL Listed to UL 467 grounding standards (as
is our lay-in lug, which is UL Listed directly by UL). The solar module
manufacturers are (slowly) changing their installation instructions to allow
them. Evergreen, REC, Mitsubishi, Sharp, Kyocera, Unisolar, and Suntech
approve WEEBs and Wiley has their documentation on their
<http://www.we-llc.com/WEEB.html> website. SunPower at this time does not
approve them, but Wiley is working with SunPower to remedy that.

However. Only the latest edition of the National Electrical Code (NEC-2008)
has wording that approves of WEEB equipment, but there are many areas of the
country that have not yet adopted the 08 Code. Because of this, many
electrical inspectors are not allowing WEEBs. Oregon and Colorado seem to be
particular problem areas, but all dealers should discuss WEEB equipment with
their local inspector to determine if they will be approved. I think that
this is just a temporary problem, but a problem none-the-less.

Additional WEEB note: With the SnapNrack, use the WEEB PMC washers to ground
the modules to the rails. The WEEB lugs, and WEEB splices can be attached to
the SnapNrack rails by drilling a hole in the side of the rail for the WEEB
bolt to go through. Wiley Electronics is working on making custom parts for
the SnapNrack, which should be available soon.

Additional additional WEEB note: The WEEB washers can only be used with the
SolarMount Top-Mount clamps, not the Back-Mount clips, and not with
SunFrame. With back-mount clips, and SunFrame, use one WEEB lug (or our
lay-in lug) on each module, and one lug per frame rail.

================================================== T

Carl Emerson

Free Power Co.

Land line +64 9 473 4286

Mobile +64 22 630 9689

Email   emerson at freepower.co.nz

Web   www.freepower.co.nz

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