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 emer...@freepower.co.nz Web www.freepower.co.nz
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