Always with the questions. This time grounding.

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Dr. Dickie

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Sep 23, 2020
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286
I've read that when you do separate earth grounds at an array - it can setup a potential between other grounding points and actually be counter-productive. I presume this is why the electrician that did the roof portion of my system tied it into the house ground - e.g. probably rebar thru concrete foundation? - instead of doing an separate earth ground.

I have no idea on this - the more I researched grounding in terms of multiple ground points it seemed to be a mystic art with many opinions! :)


When I did my roof mount, I used the IronRidge system that bonds panel frames to the rails and the rails and the electrician grounded all this into the house ground. There are lightning arrestors in place outside at the combiner - so the ground wire is just 8 AWG.

When I did my DIY ground mount of galvanized pipe + universal strut + universal strut bolt accessories (to hold panels in place).....
View attachment 26559

the universal strut is all bonded to the galvanized pipe via metal tapping screws like this:
View attachment 26561
The vertical/horizontal galvanized pipe is bonded like this:
View attachment 26562
And the panels are threaded with grounding wire like this.... (FYI - the panels came with holes for this.)
View attachment 26563

And it's all grounded to the house ground (with lightning arrestors out at the array/combiner box) with 6 AWG twisted copper in the pic above.

I believe this is how it should be... but who knows! An electrical engineer friend (or maybe @Korishan :) ) - someone told me these bonds will likely corrode over time (like 10yrs) and not be very effective.

However, I did discover that one can actually do some tests using an Ohm meter with really long leads to verify that bonding is good / within accepted specs - but I don't remember the details. :)
I am in the process of bonding and grounding the panels (I have some more of the clips coming later today). Are far as corrosion, that is why NEC requires stainless steel clips to do the bond between aluminum panels and the 6 AWG copper conductor. Copper to aluminum will corrode, stainless to either aluminum or copper will not--at least not as easily or quickly.
Please tell me that code does no require that galvanized pipes that screwed together do not need grounding straps between them. And that the struts bolted together do not need individual grounding straps to each ONE!!:eek:
Good gosh, I will be here for weeks trying to do that! They are bolted together, I checked, no resistance between them.
Of to try to understand more of the NEC!
Also, OffGrid, what lightening arrestors are you using? If you know, it you don't, don't go to any bother, I will figure it out--pretty sure Midnite solar has some.
 

OffGridInTheCity

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Dec 15, 2018
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1,863
I am in the process of bonding and grounding the panels (I have some more of the clips coming later today). Are far as corrosion, that is why NEC requires stainless steel clips to do the bond between aluminum panels and the 6 AWG copper conductor.
I used 6 awg bare/twisted copper wire with xx (not sure of name) to bond to the panels (and universal strut panel mounts) with steel self-tapping screws + those xx 'things' have rough edge to bite into the panel frame and universal strut metal.
1639158201533.png


Copper to aluminum will corrode, stainless to either aluminum or copper will not--at least not as easily or quickly. Please tell me that code does no require that galvanized pipes that screwed together do not need grounding straps between them. And that the struts bolted together do not need individual grounding straps to each ONE!!:eek:
As shown in an earlier post in this thread - I used self-tapping screws to bond the universal strut to the galvanized pipe.
The 'screwed together' pieces are perfectly OK and I used anti-corrosion WD-40 type product - no corrosion on the threads so far (2 years now).
I did you a strap between the horizontal and a vertical galvanized to ensure bonding thru the aluminum connection piece. The allen wrench tighteners in the side of the aluminum piece 'pierce into' the galvanized pipe to complete the bonding.
1639158409365.png

Between rails (universal strut), panels, and frame - there are many bonding's and I believe all is good / to code. If you put an ohm meter on any panel or place on the array it will be connected to ground.

Good gosh, I will be here for weeks trying to do that! They are bolted together, I checked, no resistance between them.
Of to try to understand more of the NEC!
Also, OffGrid, what lightening arrestors are you using? If you know, it you don't, don't go to any bother, I will figure it out--pretty sure Midnite solar has some.
I used MidNite Solar MNSPD-600(s) Lightning arrestors - https://www.solar-electric.com/mnspd600.html
As I understand it - you need one of these for each pair of wires going into the house from the array. That's why I have 4 of them on this combiner box. I believe this will stop any surge on all wires leaving the array and going under the house - to protect the house wiring.
1639159010712.png

I have 4 x sets of wires leaving this array and going under the house because....
1) A 3s is paralleled under the house with one of the 3s4p arrays on the roof.
2) Another 3s is paralleled under the house with the other 3s4p on the roof.
3) A 3s4p going into the house that parallel's with #4
4) A 2s that connects with the 3'rd panel on the gazebo and joins #3 under the house.
*Complicated - but results in 3 arrays of 3s5p going to 3 Midnite Classics :)
 
Last edited:

Dr. Dickie

Member
Joined
Sep 23, 2020
Messages
286
I used 6 awg bare/twisted copper wire with xx (not sure of name) to bond to the panels (and universal strut panel mounts) with steel self-tapping screws + those xx 'things' have rough edge to bite into the panel frame and universal strut metal.
View attachment 26608


As shown in an earlier post in this thread - I used self-tapping screws to bond the universal strut to the galvanized pipe.
The 'screwed together' pieces are perfectly OK and I used anti-corrosion WD-40 type product - no corrosion on the threads so far (2 years now).
I did you a strap between the horizontal and a vertical galvanized to ensure bonding thru the aluminum connection piece. The allen wrench tighteners in the side of the aluminum piece 'pierce into' the galvanized pipe to complete the bonding.
View attachment 26609
Between rails (universal strut), panels, and frame - there are many bonding's and I believe all is good / to code. If you put an ohm meter on any panel or place on the array it will be connected to ground.


I used MidNite Solar MNSPD-600(s) Lightning arrestors - https://www.solar-electric.com/mnspd600.html
As I understand it - you need one of these for each pair of wires going into the house from the array. That's why I have 4 of them on this combiner box. I believe this will stop any surge on all wires leaving the array and going under the house - to protect the house wiring.
View attachment 26610
I have 4 x sets of wires leaving this array and going under the house because....
1) A 3s is paralleled under the house with one of the 3s4p arrays on the roof.
2) Another 3s is paralleled under the house with the other 3s4p on the roof.
3) A 3s4p going into the house that parallel's with #4
4) A 2s that connects with the 3'rd panel on the gazebo and joins #3 under the house.
*Complicated - but results in 3 arrays of 3s5p going to 3 Midnite Classics :)
All of the struts I used are stainless, and all bolted together. As I said, I get no resistance between any of them--but I guess I will try to add some bond points on them too. I also used 6 AWG copper to bond all the panel frames. I am going to run that to the ground buss bar in the combiner box, then out to the shed.
I have 4 pos and neg (4 strings), so I guess I will need to get 4 of the Midnite arrestors. But I don't think I will have all four of the side cutouts like you have yours, as I will need one for the grounds--or maybe I can sneak them in the back.
Dang seeing how neat you have all your wire runs make my set-up look like redneck engineering
 

Redpacket

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Feb 28, 2018
Messages
1,341
Thanks for the reply. But since there is basically no connection between PV array and electrical system of the house,--at least not ground wise, I don't get this. If the ground on the PV structure is raised due to lightening near by, that does not affect the PV voltage send to the solar shed (since the PV is just the neg/pos from the panels, no ground involved and not referenced to ground, just to each other), so I don't see how that effects the ground of the electrical system of the house.
Sorry for the late reply, been away...
Below might have been covered already....
What you're saying can be true for "normal" voltages but there's two conditions where hazards occur:
- fault conditions that cause something to be at an unsafe elevated voltage, human touches something, gets shock.
- lightning which is 10's or 100's of thousands of volts & will easily jump between frames, cells, wires, across transformer insulation, etc, etc.

At the least, the panel frames & mounting structures should be connected to the house ground.
 

Dr. Dickie

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Joined
Sep 23, 2020
Messages
286
Sorry for the late reply, been away...
Below might have been covered already....
What you're saying can be true for "normal" voltages but there's two conditions where hazards occur:
- fault conditions that cause something to be at an unsafe elevated voltage, human touches something, gets shock.
- lightning which is 10's or 100's of thousands of volts & will easily jump between frames, cells, wires, across transformer insulation, etc, etc.

At the least, the panel frames & mounting structures should be connected to the house ground.
Yeah, thanks.
What I THOUGHT were isolated, were not. I am in the process of putting everything grounded to the house system--single point.
 
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