Lay-in grounding lugs

[ggunn]

Is there any reason why we shouldn't use copper rated aluminum lay-in lugs on module frames? I know that tin plated copper is the de facto standard and unplated copper is right out, but my installers are asking me about the (much cheaper) aluminum ones that are copper rated. I have a nagging feeling that there is some point against using them, but I cannot remember what it is.

 

[jaggedben]

Is there any reason why we shouldn't use copper rated aluminum lay-in lugs on module frames? I know that tin plated copper is the de facto standard and unplated copper is right out, but my installers are asking me about the (much cheaper) aluminum ones that are copper rated. I have a nagging feeling that there is some point against using them, but I cannot remember what it is.

Are they direct burial rated? A lot of industry literature calls for that.

My intuition is that such a lug would be fine but the set-screw part should also be suitable for outdoors (i.e. stainless steel not zinc plated).

Or, ask the manufacturer if their product is suitable for grounding modules.

 

[SolarPro]

There are definitely tin-plated aluminum lay-in lugs available now with stainless steel set screws:

http://www.elecdirect.com/product/4bba11c5-ee40-493e-a649-e15b34f445f0.aspx

They are not rated for direct burial, but most PV systems are not installed below grade.

I saw BB's question and the Northern AZ & Sun forum, and can't find any tin-plated aluminum lugs that are listed to UL 2703. However, it doesn't look like many of the the standard tin-plated copper, direct-burial-rated lay-in lugs are listed to UL 2703 either. This solution from Amphenol is listed to UL 2703, but seems to be an exception to the rule:

http://www.amphenol.com/about/news_archive/2011/93/

Tin-plated aluminum might not be appropriate for all environments?direct-burial-rated lugs obviously provide better corrosion resistance?but there must be environments where a tin-plated aluminum lug with a stainless set screw would work just fine. Hard to say whether they could pass the UL 2703 tests until someone actually goes to the trouble and expense of doing the testing.

It sure would be nice to have a lug that works in applications where corrosion isn't a concern and only costs 50% what tin-plated copper lugs go for. Some BOS costs will be hard to drive down, but the best equipment grounding solutions for PV are probably still to come.