I'm working on a project that will use Unirac's Sunframe rails for a multiple row solar array. I'm having trouble figuring out the best way to electrically ground these rails using any of the grounding lug products available on the market. Does anyone have any experience with these rails?

Thanks,

Scott.

Why are looking to ground the rails?, for code compliance, you need to ground each and every solar panel frame, a mechanical bond to the mount structure is not a code approved method

Well, in reading the discussion on grounding in this document "Photovoltaic Power Systems and the National Electric Code" located at http://www.nmsu.edu/%7Etdi/Photovoltaic ... Pract.html gives me the impression that electrically grounding the mounting racks in addition to the panels themselves is a good practice. I agree it is not required by code. I guess a general question is if anybody is really doing it.


Scott.

on a side note, I posted an thread regarding UFER grounding here.
http://www.wind-sun.com/ForumVB/showthread.php?t=3583

has nothing to do with rails, other than a place to attach the ground wire to.

if you want to add the extra step for the rails i suppose there's nothing wrong with that if it's done right. do not break the ground wire run already going from the pv frames, but just add a connection to it via a split bolt and the same gauge of copper wire used on the frame grounds. now i'm not sure the best place to attach to on the rails, but try to use stainless steel connections so that the copper wire does not contact the aluminum rails directly as this will cause a galvanic reaction (rust). unirac can say for sure on where and how a good ground connection can be made to the rails.

I do want to add the extra step and have already been doing it for installs using Unirac's Solarmount rails. For the Solarmounts I use a WeebLug for the rail ground connections and it works great. There just really isn't an equivalent product for the Sunframe rails so I was trying to see if anyone had a good solution that wasn't along the lines of drilling a hole through the rail. scrapping the anodization off, and using the same lug and stainless steel bolts, washers, and nuts that are used for the modules themselves. Workable, just not quite as elegant.

Scott.

that looks like a viable way of doing it. you should do it for each rail run ideally, but if you must go with only one of them then it should be the rail run that is highest in altitude and above the other rail runs.
just so i don't confuse anybody i use the term rail run meaning that many rails can be tied together and are continuous as in a straight line.

ARRGH !! You should never scrape anodized alum off. You are leaving bare metal exposed, and it WILL :
1) oxidize to poor conductor before you can get a screw into it (seconds)
2) continue to corrode from the scraped area, and eventually the screw threads will fall off.

I looked up the WEEBLug http://www.we-llc.com/WEEBLug_story.html just to see what they were. Their literature states: "Specialized teeth on the washer are constructed to embed into anodized aluminum and establish a gas-tight electrical connection." Breaking the anodized layer anyplace where is is not gas tight, will allow O2 to get in and corrode it. Self-taping threads into aluminum are fairly gas tight (if the pilot hole is not too big).

Look at old aluminum on a roof after 10 or 15 years, every raw end cut, drilled hole, and scratch, have started their decline into white powder.

i am told unirac is working on an answer for this thread and i will either update you on what i know or that you will be addressed directly by unirac.

Mike,

Perhaps I wasn't clear enough. The procedure of scraping the anodization off is localized to where the grounding lug is being placed into contact with the rail itself. The idea is to follow the same procedure recommended for grounding the panels in the document I sited in a previous post to this thread. In particular, we are following the recommendations in Appendix G. After the anodization is removed around the ground hole on the panel, an anti-oxidant is applied both to the exposed aluminum and the grounding lug. The grounding lug is then placed on top of the exposed aluminum and, of course, mechanically secured with stainless steel hardware through the lug and panel holes. This, in my opinion, is a much better electrical ground than relying of the threads of a self-tapping stainless steel screw through a pre-drilled hole in the aluminum panel. And I think it can be applied equally well to the rails themselves in the absence of a specialized solution like the WeebLug for the SolarMount rails.

Scott.

Scott,
This solution was purposed to me by an engineer at Unirac: Using the lugs designed for the SunFrame (identical stye as Weeb.) Drill a hole throuth the cross section of the rail that will pass through the cavity hole in the rail and then use a stainless nut and bolt to attach the lug. The lug has cutting nubs that penetrates the anodization and gives a solid mount.

-Rick-

rick,
maybe scott knows what you're talking about, but i'm thinking some pics might be helpful in letting me visualize what that solution entails.
edit to add that now i picture in my mind what they are proposing so nevermind the pics.

Their literature states: "Specialized teeth on the washer are constructed to embed into anodized aluminum and establish a gas-tight electrical connection." Breaking the anodized layer anyplace where is is not gas tight, will allow O2 to get in and corrode it. Self-taping threads into aluminum are fairly gas tight (if the pilot hole is not too big).

From your PDF, Apx G.
" The Belleville washer provides
uniform tension, and a torque screwdriver should be used for all electrical connections. See
Figure G-2. Some new grounding lugs have been listed for use without the anti-oxidant
compound since the design of the lug penetrates the oxidation. It is not acceptable to use the hexhead,
green grounding screws (even when they a have 10-32 threads) because they are not
suitable for outdoor exposure and will eventually corrode. The same can be said for other screws,
lugs, and terminals that are not suitable for outdoor applications."

What they did not cover was to skip abrading the aluminum frame, if you use the SPECIAL toothed washer, at the proper torque, as prescribed by the Mfg. A dab of anti-ox before the install won't hurt, but I doubt that stuff lingers long in the weather outdoors.

In the spacecraft industry, we use either gold plate over the aluminum housing, or something called "Chemfilm" which is a clear conductive coating over the entire part, applied somewhat the same way as anodizing. I suspect in the future, the official panel grounding point, will either have a clear chemfilm coat, copper/tin electroplate or gold flash, to insure a long lived, good contact.

I contend that using the WEEBLug http://www.we-llc.com/WEEBLug_story.html parts, or an equivalent, will give the best grounding, over 25 years, and certainly much better results after several years of weather, over a bolt/anti-ox/bare aluminum.

Or we may just continue to disagree. Aluminum holds up for about 5 years in my area (coastal Los Angeles) and then, generally turns to powder, unless it's been protected somehow. I've seen hollow I & L beams, where tooling has sat outdoors in a storage yard, and the anodized skin lasts, but the inner core rots out. Very light weight though!

I don't think we disagree as much as you think we do. I'm already employing the WeebLug product to ground the mounting rails on systems installed using Unirac's SolarMount rails. I don't do any removal of the anodization on these rails and rely on the puncturing of the anodization provided by the WeebLug. But for the panels themselves I do employ the method outlined in Appendix G. Quoting their recommended procedure for the panels more fully...

"For those situations requiring an equipment-grounding conductor larger than 10 AWG, a
stainless-steel #10 screw, nut, flat washers, Belleville spring and lock washers can be used to
attach an ILSCO GBL4 DBT, Burndy CL50-DB-T, or equivalent lug to the module frame at the
point marked for grounding. See Figure G-1. Before attaching the lug to the module, a stainless-
steel brush should be used to remove any anodization or oxidation from the aluminum module
frame, and a thin coat of anti-oxidant film should be placed on the clean aluminum surface.
Burndy Penetrox A-13 or equivalent should be used. The flat washers are required to prevent the
lock washers from digging into the soft copper or aluminum. The Belleville washer provides
uniform tension, and a torque screwdriver should be used for all electrical connections. See
Figure G-2. Some new grounding lugs have been listed for use without the anti-oxidant
compound since the design of the lug penetrates the oxidation. It is not acceptable to use the hex-
head, green grounding screws (even when they a have 10-32 threads) because they are not
suitable for outdoor exposure and will eventually corrode. The same can be said for other screws,
lugs, and terminals that are not suitable for outdoor applications."

Now I have a system where I'm going to mount the panels using Unirac's SunFrame rails instead of Solarmount rails. And I want to electrically ground the rails. I would use the WeebLug if it was possible, but it is not readily compatible with the SunFrame. So my original question was how are other people grounding SunFrame rails. One possibility I suggested was applying the same method to the rails that I do to the panels. Another might be trying to use the WeebLug. In either case there is no good solution that doesn't involve drilling a hole in the SunFrame rail.

And if you object to the method of grounding the rails I suggested, which is equivalent to the grounding method I'm using for the panels, then I guess you think that my method of grounding the panels is also suspect.

Scott.

Rick,

When you say use the lugs designed for the SunFrame, I was not aware that there were grounding lugs available for the SunFrame rails that worked like the WeebLug does for the SolarMount rails. Or are you just suggesting I use the WeebLug via a hole drilled into the SunFrame rail below where the panels sit?

Scott.