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Electrical grounding of Unirac SunFrame rails
http://solar-guppy.com/forum/viewtopic.php?f=4&t=693		 Page 1 of 2
Author:  solartek [ Fri Sep 19, 2008 3:44 pm GMT EthGMT ]
Post subject:  Electrical grounding of Unirac SunFrame rails
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.
Author:  Solar Guppy [ Fri Sep 19, 2008 3:48 pm GMT EthGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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
Author:  solartek [ Fri Sep 19, 2008 4:33 pm GMT EthGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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.
Author:  mike90045 [ Sat Sep 20, 2008 1:44 pm GMT EthGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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.
Author:  niel [ Sun Sep 21, 2008 3:11 am GMT EstGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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.
Author:  solartek [ Mon Sep 22, 2008 4:53 pm GMT EndGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame 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.
Author:  niel [ Mon Sep 22, 2008 6:59 pm GMT EndGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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.
Author:  mike90045 [ Tue Sep 23, 2008 9:51 am GMT ErdGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
solartek wrote:
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.


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.
Author:  niel [ Tue Sep 23, 2008 1:25 pm GMT ErdGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
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.
Author:  solartek [ Tue Sep 23, 2008 1:42 pm GMT ErdGMT ]
Post subject:  Re: Electrical grounding of Unirac SunFrame rails
mike90045 wrote:
solartek wrote:
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.


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.


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.
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