Solar Ground Woes

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lile001

lile001

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Midwest
Solar Ground.jpg

Attached is a photo of a ground lug on a solar panel. This installer is going around installing dozens of them like this, and the inspectors don't mind at all since they've never seen solar panels before anyway and don't know better. Here is the setup:

Aluminum solar panel frames are mounted on a galvanized steel frame. There is no aluminum mounting rail nor WEEB. As galvanized steel is not a decent conductor, the installer has added a copper ground wire, using the type of lug shown in the picture. The lug is attached with a self-tapping screw, but I could not tell if it was a galvanized steel or stainless steel self-tapping screw. It looks like a bugle head (cone head) screw, with no toothed lock washer underneath it. The lug looks like it is listed for CU-AL. This ground connection is accessible from the bottom, as it is a grade-mounted array, so it could presumably be removed if a panel was being serviced by removing the self-tapping screw. I suppose this satisfies 690.4(C) which requires that removal of a panel does not interrupt the ground for another panel. If this was a roof mounted array I don't see how it would comply. The installer used Noalox goo on the copper wire, I suppose to keep the copper and nearby aluminum from corroding. Will that wash off in the rain? Does it even work on copper?

OK, let's see how many things we can find wrong with this grounding installation? I think there are several but I'd like to get some other opinions.

What could be changed to make it right?
 
lile001 said:
...

What could be changed to make it right?
Click to expand...
The self-tapping screws for certain (...moot point, but the one in the photo appears to be pan-head type to me). Screws must have machine threads (see 250.8).

Lugs (or whatever is used for connection of the EGC) must be listed for the purpose of module or frame grounding. I am uncertain the pictured type are so listed.

The 2011 NEC has managed to squeeze in the word "identified" in conjuction or in lieu of the term listed. I consider a welded galvanized steel frame as a good grounding conductor... but is it "listed" or "identified" for the purpose of PV grounding???

The use of Noalox is neither required nor prohibited.
 
If I were commissioning this system. all compliance issues aside, I would ask the installer to use the same type of "lay in lug" ground lugs that are used when installing aluminum modules. These are usually rated for several different types of metals. I think I would also ask for a bolt through style or at least self threading machine screw like the module manufactures require. Plus a lay in lug allows the module or equipment to be removed without interrupting the ground path.
 
In 2011, I think there it's a very close call to say 250.8 (5)(but there's no nut) verses (6)!

I don't think they made it with the requirements of (6), either.
 
I do not see any attached photo. Could it be my browser (Mozilla Firefox)?

The grounding connection is sort of a two-step approach with the UL Listing and NEC.

Basically the manufacturer submits PV modules for testing to UL-1703 along with the proposed installation instructions and samples of the grounding connection(s) to be used. Modules must pass the grounding tests using the manufacturer approved methods.

The modules are to be supplied to the end installer with the approved instructions and installed according to the instructions.

Modules are to be grounded at one of the indicated points by one of the indicated methods. This means that the acceptable method varies by the module and even by the date of the testing. Some manufacturers allow a turn of solid copper wire with stainless steel washers, screw, and nut. Others specify a lay-in lug and state that it to be attached according to the lug manufacturer's instructions. Always insist on getting the instructions, always read the instructions. Some AHJs have their own desires after attending classes on inspecting PV systems.

So far I have not seen any manufacturer specify a self-tapping screw. The general rule that UL applies is that a grounding hole must engage a full two threads, hard to do with the course threads on self-tapping screws.
 
BillK-AZ said:
I do not see any attached photo. Could it be my browser (Mozilla Firefox)?
Click to expand...

The link is really hard to see - the very first line of my original post has the words Solar Ground.jpg, but it is not underlined like a normal-looking link so you don't know to click on it. It does open up in Forefox, however.
 
Smart $ said:
The self-tapping screws for certain (...moot point, but the one in the photo appears to be pan-head type to me). Screws must have machine threads (see 250.8).
Click to expand...

250.8 Connection of Grounding and Bonding
Equipment.
(A) Permitted Methods. .......
(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut

In the past, to prevent galvanic corrosion problems, I have bonded aluminum solar panel frames to stuff with aluminum machine screws, and adding stainless steel toothed lock washers to allow it to bite into the metal. Since aluminum comes automatically with a coating of aluminum oxide, I thought this would make a better connection. It looks like a steel or zinc plated steel machine screw fastener would also follow the letter of the code, is that right?
 
ocoee said:
If I were commissioning this system. all compliance issues aside, I would ask the installer to use the same type of "lay in lug" ground lugs that are used when installing aluminum modules. These are usually rated for several different types of metals. I think I would also ask for a bolt through style or at least self threading machine screw like the module manufactures require. Plus a lay in lug allows the module or equipment to be removed without interrupting the ground path.
Click to expand...

I'll bet the installer got sticker shock when he found out many of these lay-in-lugs are $5 a pop. Here is a lay-in lug that is more reasonable, $1.84, and it is made out of aluminum already:

http://www.mrsupply.com/ilsco-ground-clamp-lug-gbl-4.html

Here are a few more reasonably priced ones

http://www.elecdirect.com/catalog/df208983-6f76-455f-b7b7-91bc983c6c39.aspx

It is extremely difficult to tell if any of these are listed specifically for solar grounding, and I question whether that is really required, or if a lug that is simply listed for outdoor use and for grounding is sufficient. Is there specific language requiring "listed for grounding solar panels" in the code? Where?
 
lile001 said:
View attachment 5378

If this was a roof mounted array I don't see how it would comply.
Click to expand...

I said this, because a standard roof-mounted array with racks flat to the slope of the roof would not allow any access to the back of the panel to remove this lug, whether it was lay-in or not.

Removal of the self-tapping screw wouldn't satisfy the requirement for removal either, because when you re-insert the self tapping screw you have damaged the hole, and it will be loose the next time. Not to mention it is the wrong kind of screw in the first place. I think he's violated the requirement for removal without interrupting the ground path.
 
lile001 said:
... Is there specific language requiring "listed for grounding solar panels" in the code? Where?
Click to expand...
Here's what the Code says...
690.43 Equipment Grounding. Equipment grounding conductors
and devices shall comply with 690.43(A) through (F).
(A) Equipment Grounding Required. Exposed non?
current-carrying metal parts of PV module frames, electrical
equipment, and conductor enclosures shall be grounded in accordance
with 250.134 or 250.136(A), regardless of voltage.
(B) Equipment Grounding Conductor Required. An
equipment grounding conductor between a PV array and other
equipment shall be required in accordance with 250.110.
(C) Structure as Equipment Grounding Conductor. Devices
listed and identified for grounding the metallic frames
of PV modules or other equipment shall be permitted to
bond the exposed metal surfaces or other equipment to
mounting structures. Metallic mounting structures, other
than building steel, used for grounding purposes shall be
identified as equipment-grounding conductors or shall have
identified bonding jumpers or devices connected between
the separate metallic sections and shall be bonded to the
grounding system.
(D) Photovoltaic Mounting Systems and Devices. Devices
and systems used for mounting PV modules that are
also used to provide grounding of the module frames shall
be identified for the purpose of grounding PV modules.
(E) Adjacent Modules. Devices identified and listed for
bonding the metallic frames of PV modules shall be permitted
to bond the exposed metallic frames of PV modules
to the metallic frames of adjacent PV modules.
(F) All Conductors Together. Equipment grounding conductors
for the PV array and structure (where installed)
shall be contained within the same raceway or cable or
otherwise run with the PV array circuit conductors when
those circuit conductors leave the vicinity of the PV array.
Click to expand...
 
lile001 said:
I said this, because a standard roof-mounted array with racks flat to the slope of the roof would not allow any access to the back of the panel to remove this lug, whether it was lay-in or not.

Removal of the self-tapping screw wouldn't satisfy the requirement for removal either, because when you re-insert the self tapping screw you have damaged the hole, and it will be loose the next time. Not to mention it is the wrong kind of screw in the first place. I think he's violated the requirement for removal without interrupting the ground path.
Click to expand...

It is not as difficult as described. The lay-in lugs are normally assembled onto the PV modules before the modules are placed on the mounting rails. Then, as the module is being positioned, the grounding wire is placed into the lay-in lug and the screw on the lug tightened just before the module is lowered into place.

If service is required, there will then be enough slack in the grounding wire so that the wire can be disengaged from the lug. This is why lay-in lugs are used.

The 690.43 posting by Smart$ must be the new 2011 Code version. I have no doubt by the time the 2011 version is generally adopted, there will be lay-in lugs or equal that are identified and listed for bonding the metallic frames of PV modules.
 
Are the lugs in the picture even listed for a wet location, not even touching the requirement for solar use listing
 
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