Grounding of Solar Panels and Rails

[silverstone]

I installed all the solar panels on my roof by following the advice of the guy that sold me the mounting system. Should never trust a sales person .

He told me that here (in Denmark) it's not required (by law) to ground a Solar Installation.

As such now, all of the panels and Rails are floating (not grounded).


After talking with a experienced engineer, he advises to have them grounded. Not sure how much it would help in case of lighting (6mm2 would evaporate quite fast ...), but at least to detect earth faults in a string etc (would register as a low insulation resistance value, thus causing the inverter to trip).

The simplest would be to just ground the edges of the mounting rails, but that's probably not a good connection at all. The extensions between rails are not really meant for an electrical connection. Also because Aluminium very easily oxidizes, and we didn't "scrub" it before installing (was supposed to be just a mechanical connection).



The better and proper approach would be to ground every frame individually. But I'm not really a squirrel so going on a pitched roof is very uncomfortable for me at the very least. Even more now that it's full with solar panels ....

Plus I'm not really sure how to ground them properly, especially in terms of galvanic corrosion.

The Installation Manual of my Panel reccomends using Copper or Copper Alloy wire, together with some TE Connectivity SOLARLOK Grounding Clips (currently not in stock anywhere, in metric units M6/M8 I would assume, only 8/32'' or similar are in stock):


So I'm left with 2 choices really:
- Aluminium Wire: Smallest I could buy is 1G50 mm2. Plus Aluminium Lugs. Corrosion prevention/protection paste when crimping and screwing to the frame of the panel.
- Copper wire: probably 1G6mm2 due to cost. Plus Aluminium/Copper (bimetallic) lugs which cost a fortune.

For some reason my installation manual (in chenglish) reccomends COPPER wire DIRECTLY on an Anodized ALUMINUM frame. And the Solarlok Grounding Clip is also listed as some Copper alloy. And the process of "properly attaching" the ground connection is to use a toothed washer to "scrap away" the anodization and oxide most likely ...

What is going on here ? Shoudldn't there be a need for bimetallic lugs or just use aluminium all the way until a small box with terminals able to accept Cu/Al ? And from there just go down to the Earth rod (galvanized steel typically) ?

Thanks for your insights .

 

[octal_ip]

The method and best practice of grounding is usually specified by your mounting hardware manufacturer and local compliance standards. Here's a good reference that gives an idea of how it all works in a typical system:

https://www.clenergy.com/wp-content/uploads/2020/06/Clenergy-PV-ezRack-Grounding-System-Installation-Guide-V1.1.pdf

In summary:

1. Grounding clips are used to provide a conductive path between the panel frames and rails, and grounding lugs connect the rails to a ground wire.
2. Both the clips and lugs have sharp interfaces that pierce the anodised layer on the panel and rail to ensure good conductivity.
3. The clips are single-use, and must be replaced if they're ever released.
4. Every rail must be connected to your ground wire through a lug, as a good enough conductive path between rails through the panels isn't reliable.
5. The gound wire is there to protect people, all bets are off if there's a lightning strike. 6mm² copper is typical and usually enough to achieve a low enough resistance from the lugs to ground.

In terms of galvanic corrosion at the copper/aluminium interface, I've not seen this addressed in any of the documentation, though I've seen recommendations to use a "cold gal" type paint (i.e. high in zinc) to coat the wire and screw interface after tightening to prevent any corrosion.

 

[silverstone]

This seems OK ... Except that it's only for the rails and I don't seem to be able to source this anywhere .




My engineer friend reccomended using a stainless steel wire instead of an aluminum/copper cable for the main runs. I guess I could run this in parallel with each aluminium rail row (maybe only one out of two, that would make it "much" easier to run). But I'm not sure if I can let the stainless wire in direct contact with the aluminium rail all the way due to galvanic corrosion possibility (e.g. cable tie the stainless wire to the aluminum rail, e.g. 20 meters for each rail).

I would assume he meant to pigtail from it with another stainless steel wire or maybe Copper/Aluminum Wire ?





Or maybe something like this:


He also recommended adding some dielectric grease to prevent corrosion.

But I am still scared of going on to the roof ... There is not much place to walk and grounding each panel individually requires putting some screw behind the panel in an awkward position with the risk of damaging the backside of the panel (which is usually very fragile).

Any tips ?

I know "a posteriori" it's probably easy ... It should have been grounded sooner. It's almost 2 years and it's still not operating. But what can be done now ?

 

[kshaw]

To get rid of any corrosion, you want to spray with ACF-50. That stuff is awsome and has ressurected so many electrical devices for me that it deserves some kind of an award.

 

[timselectric]

To avoid galvanic corrosion. Use lugs that are dual rated for aluminum and copper. And make sure that the bare copper only comes in contact with the lugs.

 

[silverstone]

To avoid galvanic corrosion. Use lugs that are dual rated for aluminum and copper. And make sure that the bare copper only comes in contact with the lugs.

Those bimetallic lugs are typically hard to source and EXTREMELY expensive though.

 

[silverstone]

Maybe something else from DEHN like the clamp ...

That still doesn't solve how to easily and without damaging attach it to the panels ...

 

[timselectric]

Those bimetallic lugs are typically hard to source and EXTREMELY expensive though.

Pretty common lugs.

Lay in Connector, Pool Bonding Lug with Corrosion-Resistant and High-Conductivity Aluminum for Grounding Swimming Pool and Conduits, 4-14 Wire Range(10 Packs) https://a.co/d/errFHC5

 

[silverstone]

Pretty common lugs.

Lay in Connector, Pool Bonding Lug with Corrosion-Resistant and High-Conductivity Aluminum for Grounding Swimming Pool and Conduits, 4-14 Wire Range(10 Packs) https://a.co/d/errFHC5

Not sure I see how to connect that to each panel frame though. I only have some holes on the long side of the panel. And this means only 2 panels connected that way ...

 

[timselectric]

Not sure I see how to connect that to each panel frame though. I only have some holes on the long side of the panel. And this means only 2 panels connected that way ...

Put one on each panel. Run the wire through all of the lugs. Strip the wire only at the lugs.

 

[EastTexCowboy]

Put one on each panel. Run the wire through all of the lugs. Strip the wire only at the lugs.

That's exactly how I did mine.

 

[silverstone]

Put one on each panel. Run the wire through all of the lugs. Strip the wire only at the lugs.

And how do you ensure that this clamp is properly connected to the frame (oxidation, anodization, paint, ...) ?

So you would daisy chain e.g. each 1 meter long piece of copper wires bridging one panel to the next until you reach the end of the string ?

 

[timselectric]

And how do you ensure that this clamp is properly connected to the frame (oxidation, anodization, paint, ...) ?

Need to scuff the anodized surface cleen before bolting the lug to the panel. Afterwards any paint or sealer will do.
But if you are going to have to remove each panel to accomplish this task. I would recommend just using weebs. It simplifies everything. And it will provide a better grounding system for the array.

 

[timselectric]

So you would daisy chain e.g. each 1 meter long piece of copper wires bridging one panel to the next until you reach the end of the string ?

Not multiple pieces of wire.
One single wire.

 

[silverstone]

Need to scuff the anodized surface cleen before bolting the lug to the panel. Afterwards any paint or sealer will do.
But if you are going to have to remove each panel to accomplish this task. I would recommend just using weebs. It simplifies everything. And it will provide a better grounding system for the array.

I am definitively not willing to pick each panel up . That's very likely doing more damage than good, especially on the sloped roof ...

On the flat (low) roof I can go around with 1m cable and do loops, since those are relatively accessible. On another flat roof only the external panels though. The 2 innermost ones I cannot reach. And there there is no "rail" bonding ... It's a 4 x pieces of aluminum 20cm for each panel, but not continuous, on a wooden roof with bitumen on it.

And for Novotegra that I have, I didn't seem to find anything at all . They only provide this:


What are (grounding) weebs though ? I see this on Google, but I guess each rail needs a special size / hole weeb. It's not a generic thing.


What would really be nice is some pressure clips/clamps that I could but on the underside of the panel (where there are NO grounding holes). Just scrub off, apply some dielectric grease maybe, then clamp. Finish.

And then of course decide whether to use stainless steel, copper or aluminium as conductor. The Dehn Aluminium solution isn't half bad and you can "tap" off at any point of the bar and just do a small pigtail for the remaining of the length.

Is there really a difference on which side (towards the white part of the panel, or FAR away from it) you put the lug in contact with the frame ? On the BOTTOM Far away from the white part of the backside would be safer to avoid damage ...

 

[timselectric]

Weebs go between the panels or frames at the mounting bolts. They connect everything together. Then you only need to attach a grounding conductor to each separated section of the array.
As far as individually grounding each panel. You can connect to any part of the frame. Just be careful not to damage the solar cells.

 

[timselectric]

Not sure if these are acceptable by your local inspector. But, they're definitely an easier solution.

PV solar grounding clips

Our Rayvolt® grounding clip strips, electrically connects, and fastens cables in one easy, hassle free step.

www.araymond-energies.com

 

[silverstone]

Not sure if these are acceptable by your local inspector. But, they're definitely an easier solution.

PV solar grounding clips

Our Rayvolt® grounding clip strips, electrically connects, and fastens cables in one easy, hassle free step.

www.araymond-energies.com

I just saw that as well actually it looks promising, although a bit sensitive on the clamping force required. Too much and pierces cable, too little and doesn't make contact. And I don't think I can reach with a plier there.

 

[JRH]

Put one on each panel. Run the wire through all of the lugs. Strip the wire only at the lugs.

Just asking, …..I must be missing somthing….when bonding my panel's I took continuity readings and found that all 4 sides did not show any continuity with each other …be it small gap where they are cut at 45’s or oxidation ….or both ..if all 4 sides are not showing electrical contact how does just doing one piece of the frame bond all 4 pieces..
have never understood thst concept….

 

[silverstone]

Weebs go between the panels or frames at the mounting bolts. They connect everything together. Then you only need to attach a grounding conductor to each separated section of the array.
As far as individually grounding each panel. You can connect to any part of the frame. Just be careful not to damage the solar cells.

That's exactly why I'm scared to do it if it involves climbing up the roof again ?.

But each separated section of thr array... You mean when the 4m long aluminium rail joins with another sectkon of 4m rail or so? Then I think I habe 4-5 of these per each string