Always with the questions. This time grounding.


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Dr. Dickie

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I have my PV combiner box is bonded to an earth ground--8 foot rod pounded into the ground. This in turn makes the frame for the PV support structure bonded to earth ground. This is NOT bonded to the home's earth ground, as it is an isolated system--the solar charge controller is bonded to an earth ground which is a separate earth ground rod from the PV support structure earth ground, but again, it is only connected to the PV panel support structure by the positive and negative PV output--it is separate and isolated--no ground connection between the two. The inverter is bonded to the home ground system through to split phase 120V wires to the home's power panel. I think all of that is okay, if it isn't please let me know why!
Now we come to grounding the individual panels. They are not grounded to the support structure because they are anodized--so they are individual ungrounded panels.. And I see that everyone says it is important to bond all of the panels together and to a ground system. Fair enough; however, and tell me where my thinking goes astray, if the panels are separate from the support grid due to the high resistance of the anodized frames, then in the event of a lightening strike, the current would prefer the support structure which is bonded to the earth ground not the higher resistance anodized panel frames.
So, is the only reason for bonding panels together and to an earth ground just for the possibility that a broken panel may short to the support structure, and if so, then wouldn't the fact that the support structure is grounded that take care of that?
I am not against bonding all of the individual panels to ground, I just want to know why that is important.
Thanks
 

Korishan

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I would think that the metal clips that hold the panels to the frame would be the grounding the panels as well. True there is more resistance, but the thing is, if the panels were meant to have more grounding than that, wouldn't the panels be made with the grounding points? It would be wwaaaayyyyy too risky for anyone to drill a hole in the frame of the panel to tap a screw hole, so this is definitely out of the question from a manufacturers perspective.
the possibility that a broken panel may short to the support structure
I doubt that a panel could short to the frame of the panel. The amount of epoxy and glass and sealant would make this virtually impossible. In the advent that there is sufficient damage to the panel to cause leakage, there'd be major damage to several panels and possibly the whole array, so there wouldn't be any problems with shorts. I would think, anyways.
 

OffGridInTheCity

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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).....
1638803744631.png

the universal strut is all bonded to the galvanized pipe via metal tapping screws like this:
1638803830033.png
The vertical/horizontal galvanized pipe is bonded like this:
1638803887394.png
And the panels are threaded with grounding wire like this.... (FYI - the panels came with holes for this.)
1638803933819.png

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. :)
 
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Wolf

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The chance of lightning striking a "roof top" solar array is incredibly unlikely unless you are the only structure in a huge field and/or are actively seeking a strike with a 10 foot "lightning rod" attached to your roof.
That being said lightning is really just static electricity albeit at a very large scale. It will seek the path of least resistance.
Rub shoes on carpet touch door knob. Till you get close to the door knob your body is charged and relatively harmless with 20 to 25 thousand volts. Good thing its low amperage. Your solar panels with or without anodized frames offer, in lighting terms, considerable resistance to a static charge the size of a lightning strike and will seek an easier target. The purpose of grounding a solar array is that a close lightning strike produces a localized EMP that gives rise to large electrical currents in nearby wires. Many high quality charge controllers and inverters are EMP hardened and can absorb this exces as it only happens for a split second. The 'static" EMP of a lightning strike is also absorbed by the panels frame and discharged to the ground rod. With a very close lightning strike it is possible that the solar panels diodes will give out but again most are rated at that and can withstand a close strike. A direct strike to a solar array is unfortunately not survivable no matter what precautions you take but again, highly unlikely as most of the panel is glass.

With proper mounting hardware you can achieve a secure electrical bonds with both the module and the rail.
1638803814366.png
Wolf
 

Dr. Dickie

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I would think that the metal clips that hold the panels to the frame would be the grounding the panels as well. True there is more resistance, but the thing is, if the panels were meant to have more grounding than that, wouldn't the panels be made with the grounding points? It would be wwaaaayyyyy too risky for anyone to drill a hole in the frame of the panel to tap a screw hole, so this is definitely out of the question from a manufacturers perspective.

I doubt that a panel could short to the frame of the panel. The amount of epoxy and glass and sealant would make this virtually impossible. In the advent that there is sufficient damage to the panel to cause leakage, there'd be major damage to several panels and possibly the whole array, so there wouldn't be any problems with shorts. I would think, anyways.
I agree. That was my first thought. If they need to be grounded so badly, why wouldn't they provide grounding points with instructions to do so??
I wonder if this isn't a hold over from the old days when things were different, and everyone just follows along without questioning--I see this in science sometimes.
The anodizing on the panel frames is pretty good, so they are pretty isolated--I would have to scrape away some to get a good bond.
I am going to check out how isolated they actually are--goes to get DMM.
I did measure between structure and panel frame and got infinite resistance (or zero conductance).
 
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Dr. Dickie

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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 bold 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. :)
If the panels were anywhere near my house electrical system, I would agree I would bond them to that. But the panels are so isolated from the home electric (from panels to solar charge controller, then out of solar charge controller, through the system to the Inverter, and the inverter is tied to the home ground system) , I don't think a ground loop would be a problem.
That is at least what I think.
The inverter is bonded to the home electric ground system, but again, it is so isolated from everything else in the solar shed--I don't know.
I realized when typing the original post that maybe having the solar charge controller grounded to one system and combiner box to another (about 40 feet away), might cause a ground loop, but there is no common ground between them. There is only the pos and neg wires running from combiner box to solar charge controller. So my understanding is, isolated no loop.
My father in law is an electrical engineer, but he has been retired for many years and did mostly commercial work, so he likely will not know.
 
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Dr. Dickie

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The chance of lightning striking a "roof top" solar array is incredibly unlikely unless you are the only structure in a huge field and/or are actively seeking a strike with a 10 foot "lightning rod" attached to your roof.
That being said lightning is really just static electricity albeit at a very large scale. It will seek the path of least resistance.
Rub shoes on carpet touch door knob. Till you get close to the door knob your body is charged and relatively harmless with 20 to 25 thousand volts. Good thing its low amperage. Your solar panels with or without anodized frames offer, in lighting terms, considerable resistance to a static charge the size of a lightning strike and will seek an easier target. The purpose of grounding a solar array is that a close lightning strike produces a localized EMP that gives rise to large electrical currents in nearby wires. Many high quality charge controllers and inverters are EMP hardened and can absorb this exces as it only happens for a split second. The 'static" EMP of a lightning strike is also absorbed by the panels frame and discharged to the ground rod. With a very close lightning strike it is possible that the solar panels diodes will give out but again most are rated at that and can withstand a close strike. A direct strike to a solar array is unfortunately not survivable no matter what precautions you take but again, highly unlikely as most of the panel is glass.

With proper mounting hardware you can achieve a secure electrical bonds with both the module and the rail.
View attachment 26560
Wolf
Yeah, that is why I grounded the support structure for the panels. I guess I likely will bond the panels to the support structure, but I really think it is not needed.
 

Redpacket

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Here in Australia, regs are the panel frames & rails are all bonded together & tied to the house ground.
Panels are supposed to have special washers/shims that pierce the anodizing & ground cables linking between them all (mine do).
I think it's similar in the US but not sure.
With lightning it's differential voltages that get you. Eg tree gets direct hit near panel array (assuming array on different structure to house), causes ground voltage rise near array (due to separate earth stake), house's earth stake that's further away doesn't get as much voltage rise so it's a different voltage. Now you've got a problem voltage between the solar gear & the house that blows something.
Basically my understanding is you should bond everything to a single earth point.
 

Dr. Dickie

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Here in Australia, regs are the panel frames & rails are all bonded together & tied to the house ground.
Panels are supposed to have special washers/shims that pierce the anodizing & ground cables linking between them all (mine do).
I think it's similar in the US but not sure.
With lightning it's differential voltages that get you. Eg tree gets direct hit near panel array (assuming array on different structure to house), causes ground voltage rise near array (due to separate earth stake), house's earth stake that's further away doesn't get as much voltage rise so it's a different voltage. Now you've got a problem voltage between the solar gear & the house that blows something.
Basically my understanding is you should bond everything to a single earth point.
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.
IF the panels were on the roof of the house, and tied directly to the system, then yeah I see that. But that is not the case here.
I get the single earth point for ground loops (HAM radio guy here), but these are not tied together, they are separate isolated systems. The inverter IS tied to the home electrical, and so I do use the same earth ground as the house for that.
But the array is some 100+ feed away from the house electrical and not directly tied in to home electrical system.
Even the solar charge controller. While it is only about 20 feet away from the array, if lightening raised the ground for the PV structure, how is that going to effect the solar charge controller? The ground of the controller is only there to prevent a charge build up on the frame of the charge controller-my understanding, the pos/neg into the charge controller is DC and the voltages are not tied to ground (like an AC system) only tied to each other.
And just as Korishan said, if it is so important that the panel frames are to be grounded, why are there no ground connections on the panels?
I am not trying to be argumentative, please do take it the wrong way. I just don't like not understanding why I am supposed to be doing something. I don't like doing it just 'cause. If I understand why, I can make sure I do it right. Otherwise, if I am just doing it 'cause they say so, might do it wrong because I don't understand the reasoning.

Wolf said:
The purpose of grounding a solar array is that a close lightning strike produces a localized EMP that gives rise to large electrical currents in nearby wires. Many high quality charge controllers and inverters are EMP hardened and can absorb this exces as it only happens for a split second. The 'static" EMP of a lightning strike is also absorbed by the panels frame and discharged to the ground rod. With a very close lightning strike it is possible that the solar panels diodes will give out but again most are rated at that and can withstand a close strike. A direct strike to a solar array is unfortunately not survivable no matter what precautions you take but again, highly unlikely as most of the panel is glass.

Mmm, perhaps, but I still do not see how separate grounding will cause a problem. An induced pulse on the PV pos/neg to the controller will be a problem that the controller will have to handle, but how is a separate ground from the home electric going to make this problem worse. Having a close ground at the array (rather than running one 200 feet to the house) would seem to make this better, offering a quick path to ground. And the solar charge controller is not directly connected to the house, going through the system before getting to the inverter. And does the solar charge charge controller use earth ground for voltages? Or does it just use the pos versus neg of the DC in and out? It if was important for the solar charge controller to be at the same earth ground as the home, won't they say that in the info? It did not see that, only that it should be grounded for preventing charge on the frame.
Again, I see a problem if the inverter was separately grounded, since the AC system is versus ground and it is directly tied into the home system.
I hope to have time tomorrow to dig into this deeper and see if I can understand the why here.
I feel like I have entered the rabbit hole with this home solar system and battery.
But, I love learning, so I am not complaining. Just wish I was younger and had more time to really learn this stuff. Too old to get an electrical engineering degree now, and my wife told me, "No more classes." after I got a statistics degree a few years ago.
 
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OffGridInTheCity

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In my case, the Midnite Classic charge controllers are both in the house and grounded to the panels which ware grounded to the house. The output of the Inverters are grounded to the house. Its all one, shared, ground for all the electrical systems - panels, charge controllers, inverters, DC, AC. The Lightning Arrestors (e.g. surge protectors) stop a 'surge' on both the + and - from flowing from the PV arrays into the wiring downstream - so the ground is something different, I guess it's about accidentally being shocked?.

@Mr Dickie - are you saying you don't consume any AC outside of the external shed? If you could clarify the connection between your PV production, shed, inverter, and home (or other loads) I think it help understand your POV on this.
 
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Dr. Dickie

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I found this:
It says NEC says that the panels need to be grounded. However, I they say it does not have to ALL be uni-grounded to the house ground.
It seems, as suspected, the main concern is safety, not ground loops.
Kinda silly that anodize panels (which they even say are non-conductive--that is why you have to use special connectors), have to be pentrated through the anodization to get it to ground--so make it possible to get a shock to make it safe from a shock??
Yeah, I know the anodization could be missing in some spot, but really what are the odds of a panel shorting in such a way as the frame getting hot.
 
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Dr. Dickie

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In my case, the Midnite Classic charge controllers are both in the house and grounded to the panels which ware grounded to the house. The output of the Inverters are grounded to the house. Its all one, shared, ground for all the electrical systems - panels, charge controllers, inverters, DC, AC. The Lightning Arrestors (e.g. surge protectors) stop a 'surge' on both the + and - from flowing from the PV arrays into the wiring downstream - so the ground is something different, I guess it's about accidentally being shocked?.

@Mr Dickie - are you saying you don't consume any AC outside of the external shed? If you could clarify the connection between your PV production, shed, inverter, and home (or other loads) I think it help understand your POV on this.
The AC is produced in the shed, and then fed to the house. That feed from Inverter to solar panel (which is then connected to the house service panel) has a ground (three wires plus ground) going from inverter to service panel.
The combiner box from the array feeds to the Midnite solar charge controller (SSC). The combiner box is grounded to same ground as array (and apparently to the panel frames--to be in code). The Midnite SSC is grounded with its own ground. Then output from the Midnight SCC feeds into the buss bars which are connected to battery and inverter. Then, as I said, the output (and inverter) is grounded to the house ground.
That grounding just makes more sense to me, as the grounding for devices which are not ground connected to house ground are grounded close to device.
Seems silly to have to ground the panels, but apparently NEC calls for this to be done.
 
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Dr. Dickie

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Man, whoever said, "Ignorance is bliss," was spot on.
Getting into the NEC grounding rules for PV systems is mind boggling!!
Not sure my little brain can handle it all. But with holiday break coming on, I am committed (or should be committed) to trying understanding this stuff so that I need code.
 

OffGridInTheCity

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Man, whoever said, "Ignorance is bliss," was spot on.
Getting into the NEC grounding rules for PV systems is mind boggling!!
Not sure my little brain can handle it all. But with holiday break coming on, I am committed (or should be committed) to trying understanding this stuff so that I need code.
My system is 'to code' but I sure don't understand the details!
 

Dr. Dickie

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I am going to make a Word drawing of what I have and post it here and maybe on DIY solar to see if any experts on NEC can give me feedback.
I am watching videos of NEC solar grounding, but it is far from clear to me.
I just have a nagging feeling that I can going to have to dig up what I just did a week ago, to add in a ground conductor. I don't see being able to push a grounding conductor 20 feed through 4 90 degree turns--but I think I will try:LOL:.
If I have to.
 

Wolf

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Grounding, bonding to ground, bonding grounding rods etc. can and is really confusing, especially when you start to delve into the NEC code book. Article 250 Grounding & bonding and Article 690, Solar Photovoltaic Systems can be an eye glazer.

As far as house AC requirements are concerned I just know that the neutral and ground need to be "bonded" at 1 location only and that is usually at the main panel. The idea is that since "ground" has a 0V potential all other subpanels do not bond the ground to the neutral so as to never electrify the metal casing of the panel. It is also my understanding that ground rods more than 6' appart need to be bonded as there may exist a voltage potential between them at greater distances. What this has to do with an "isolated" solar array 200 feet away from the house I do not know. The only thing I can think of, is that if there is a lightning strike at or near the array the voltage potential between the 2 grounding rods (array and house) can be quite dramatic. I assume the charge controller/s are all tied to the same grounding rod as the array and the inverter is in the same "shed" 200' away and it is tied to the house ground. Is there a potential that something might "jump" the array>charge controller> inverter gap IDK. I am not an EE and I certainly don't play one on TV.

Wolf
 
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Dr. Dickie

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This is what I have:

Mmm, seems I cannot post a Word drawing.
Okay, with new knowledge, this is the corrected setup of what I have.
I actually think I am starting to know what I need. Not understand it all mind you, but know what must be done.
 

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Dr. Dickie

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Grounding, bonding to ground, bonding grounding rods etc. can and is really confusing, especially when you start to delve into the NEC code book. Article 250 Grounding & bonding and Article 690, Solar Photovoltaic Systems can be an eye glazer.

As far as house AC requirements are concerned I just know that the neutral and ground need to be "bonded" at 1 location only and that is usually at the main panel. The idea is that since "ground" has a 0V potential all other subpanels do not bond the ground to the neutral so as to never electrify the metal casing of the panel. It is also my understanding that ground rods more than 6' appart need to be bonded as there may exist a voltage potential between them at greater distances. What this has to do with an "isolated" solar array 200 feet away from the house I do not know. The only thing I can think of, is that if there is a lightning strike at or near the array the voltage potential between the 2 grounding rods (array and house) can be quite dramatic. I assume the charge controller/s are all tied to the same grounding rod as the array and the inverter is in the same "shed" 200' away and it is tied to the house ground. Is there a potential that something might "jump" the array>charge controller> inverter gap IDK. I am not an EE and I certainly don't play one on TV.

Wolf
Yeah, the code DOES allow for another earth ground rod to be at the array, but it does seem as if I have to bond that ground to the AC ground from the home service panel.
There is only one place that the neutral is bonded to the ground that is in the home service panel.
DANG IT. It seems I have to dig up everything I just did (fortunately only about a 20' run) and include a ground wire along with the pos and neg from the combiner box to shed. Then bond solar charge controller and inverter to that.
I though it was a no go to have your inverter grounded at two different spots, but I think a DC grounded to inverter and the AC ground of the inverter can be different (even though my inverter bonds DC negative to AC ground--and if I add a DC ground to that as well).
Just when I thought I had it all done correctly, I have to start all over again (sigh).
Heck who needs spare time.
 
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Wolf

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This is what I have:

Mmm, seems I cannot post a Word drawing.
In windows 10 just use the "Snip" tool capture the image then go to edit and copy.
Then just paste the image into the text box and it will upload the image.
You will see the image in the text window and as an attachment.
Backspace the image out of the text window and then either insert as full or thumbnail.
Wolf
1638907987928.png
 

Dr. Dickie

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My system is 'to code' but I sure don't understand the details!
If yours is to code, do you use the GFP in the Midnite solar charge controller? I am going through that with them right now, and they say if the combiner box bonds the DC negative to ground, then you can't use the GFP???
I am waiting to hear back from them as to why they did that then in their combiner box.
Also, on checking, it seems as if my inverter bonds DC negative to AC earth ground??? Apparently both are no go for the GFP in the Midnite SCC.
Good gosh, I have opened a can or worms with a million heads and they all point to me being screwed!
 
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