Pilot Bob
New Member
That is not correct as I read the 2020NEC. Starting at 690.41 it talks about grounding. No where does it say the array must be grounded back to the panel.
Confused by array grounding
- Thread starter Texican
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zanydroid
Solar Wizard
The quoted text says equipment grounding conductor which means it has to go back to the N-G bond by definition of EGC.
I scrubbed the Mike Holt video and it does cover the same code reference. If he made a mistake in the video there would surely be a lot of posts on his forum jumping on it.
Do you at least accept that there should be grounding back to wherever the GFP is looking for a fault to the chassis?
timselectric
If I can do it, you can do it.
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It doesn't have to go directly to the panel.
It must be connected to your grounding system.
You are required to run a EGC with the PV wires, back to the equipment that it feeds. Which in turn is required to be connected to your grounding system.
Your grounding system is created at your main panel.
timselectric
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Inspectors are supposed to be qualified. But, this one slipped through the cracks. lol
The provision you are looking at accommodates glass-glass frameless panels without a ground. Once you have metal parts on the panel you need a ground per 690.43.
Pilot Bob
New Member
1. I don’t disagree with this but when you install a ground electrode at your array you are complying with this.
2. The Neutral coming in from the grid is grounded at the substation, and every pole with a transformer and every guide wire to a pole. This is what I meant when I said you get a ground from the grid.
timselectric
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No, you're not.
The earth is not a low impedance (resistance) path.
A EGC is required for all grounding.
A ground electrode (rod) , at the array. Is an auxiliary ground electrode. And does not replace the required EGC.
While auxiliary ground electrodes are allowed. If installed, they also must be connected to the grounding system. By means of an EGC.
Pilot Bob
New Member
No, that is not correct.
No, not completely correct. 690.47A1 states the PV output circuit EGC is the only connection for ground required for the PV System. 690.47B allows you to add a ground electrode for the array. I believe all systems need to be grounded, just not a fan of the array ground going back to the ground electrode for the main panel.
ksmithaz1
Solar / EV Junkie
I would ask my local inspector why he is not in agreement with NEC, since that is clearly not what Mike Holt of the NEC has outlined repeatedly in his videos.
ksmithaz1
Solar / EV Junkie
Then you may want to spend some quality time listening to Mike Holt's video's explaining exactly why you should do what you are not a fan of. But maybe all that research by all the NEC geeks is all BS. I dunno, but I kind of lean towards accepting the recommendations of the electrical engineers that come up with this stuff.
Mesquitemonkey
New Member
All I get from this is there are 2 camps and both have good points.
Camp 1. Because your PV wire goes to something connected to a AC circuit it is now part of the AC circuit and must by NEC be equipment grounded to that circuit.
Camp 2. PV systems are a DC circuit and by NEC be equipment grounded apart from a conductor 250.... exception 1.
I say even if it turns into a AC circuit by connecting it to an inverter how the heck can a AC fault travel through DC current to cause a "deadly shock" (Dont just say it can in theory, give me proof that it has happened) .
If a fault is on the DC side it would have to be on both neg and pos to make a circuit through the panel.
So in the end do whatever camp the inspector is in and run your ground from PV to AC EGC. (NEC 2023 allows the PV EGC to be outside the wire way.)
IMO. NEC is comprised of more lobbyists than geeks
Camp 1. Because your PV wire goes to something connected to a AC circuit it is now part of the AC circuit and must by NEC be equipment grounded to that circuit.
Camp 2. PV systems are a DC circuit and by NEC be equipment grounded apart from a conductor 250.... exception 1.
I say even if it turns into a AC circuit by connecting it to an inverter how the heck can a AC fault travel through DC current to cause a "deadly shock" (Dont just say it can in theory, give me proof that it has happened) .
If a fault is on the DC side it would have to be on both neg and pos to make a circuit through the panel.
So in the end do whatever camp the inspector is in and run your ground from PV to AC EGC. (NEC 2023 allows the PV EGC to be outside the wire way.)
IMO. NEC is comprised of more lobbyists than geeks
timselectric
If I can do it, you can do it.
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I'm all for cutting corners and saving money.
But safety is not the place to cut corners.
Doing something that is unsafe for you, is only a problem for you. But Doing something that creates a Hazzard for others is just irresponsible.
Please think about the people who would assume that they are safe.
But safety is not the place to cut corners.
Doing something that is unsafe for you, is only a problem for you. But Doing something that creates a Hazzard for others is just irresponsible.
Please think about the people who would assume that they are safe.
Mesquitemonkey
New Member
I'm all about being responsible and not getting others hurt. I see the theory of grounding at existing EGC but I also see how it should be an isolated DC circuit. If an isolated circuit it should be grounded separately from existing EGC. Always ground electric equipment but the question is where.
If you put safety first than you should not put solar on the roof because more people die falling of roofs than by electric shock. I could not find one death by solar shock much less solar panel equipment shock. I figure there has been a couple out of theory but If you do things for safety sake than you would get nothing done because everything in life is deadly
ksmithaz1
Solar / EV Junkie
Perhaps, but I have family and friends that are electrical engineers, that tend to agree. Do you know what a voltage divider is? It's a common trick used in electronic circuits, to create lower voltage levels for small loads. You basically leverage the voltage drop across a resistance to get a lower voltage because MORE electricity will follow the path of least resistance but not ALL of it does. Thus when you create a secondary path with a similar resistance (or impedance/reluctance/whatever) you end up creating a voltage divider with potential at the point of diversion. You can see this yourself, get a meter and two 1Kohm resistors. Put them in series and connnect them to a 9v battery. You will read approximately 4.5v across either resistor. Now with a 1K resistor you will limit your current draw, i=e/r so 10v/1000o 10ma or something, Unfortunately a ground has a much lower resistance. maybe 1ohm (Higher in sandy soil)? So if you are dividing a 240v issue with a couple of 1ohm resistors you have the potential to grab 110v at 110a.
Now this would be an extreme/unlikely case, but the principle is the same, you want all currents to flow to the same ground to prevent creating a voltage divider/potential because the current flows down multiple paths.
YMMV, but you are grounding the frames, not the DC coming off the panels. Since all the current is coming back to the inverter if there is a problem you want the inverter to share the same ground as the panel frame. If you ground the panel 100ft away from the ground the inverter uses up at the panel you just created a voltage divider with mother earth.
Tulex
Solar Wizard
I thought the main point of Mike Holt's video was that code allows for a non connected auxiliary grounding electrode, which he was saying was a bad idea. If not, I should probably watch it again.
Not an issue for me, I ran back to my one and only EGC.
Electrically it is not an isolated DC circuit. That is the problem. You can measure an AC ripple to ground on the panels; that is pretty definitive that the "DC" is not isolated.
The thinking has unfortunately changed over the years. 30 Years ago I would have been in the local grounding electrode as a substitution for an equipment grounding conductor camp. As an independent structure no ground conductor was needed between the two. Unfortunately that has proven to be unsafe and an inaccurate way of looking at what happens-- just as people here often get confused.
The school of thought led to terrible decisions like (truly) isolated grounds and multipoint grounding until the code caught up.
I do disagree with a number of things that have been added or changed with the code over the years, but more on economical grounds than safety (or the balance thereof). This is not one of those things.
Watts Happening
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I ask this out of sheer interest and admitted “lack of understanding”. I believe I understand it, but accept that my position may be inaccurate. No part of me wants to cut corners or anything of the sort.
You have a standard American home with a main service panel and a ground rod. Let’s say you have a Sol-Ark 15k or an EG4 18k mounted next to your main panel, functionally similar units.
Now you install a ground mount array 150 feet away from your inverter, let’s call it a 10kw array.
Help me understand how the “ground wire” which in this instance is a “bonding conductor” will provide protection.
It isn’t there to protect against the DC voltage, it’s there to protect against AC voltage in the event of an equipment failure of the inverter, correct?
If the above is true, we’re now protecting against an inverter that has failed internally and is now sending out enough AC power to somehow energize the solar panels?
I’m not seeing where this supposed AC power is getting from the positive and negative wires on a solar panel to the frame itself? I’m not aware of a physical connection between them. Has anyone attempted to energize a solar panel with 120v? If not, I’ll give it a shot, I’ve got some older panels laying around.
Again I’m just trying to wrap my mind around how this current would actually flow. I suppose if you had the PV ground wire somehow bonded to the structure it becomes a theoretical possibility?
You have a standard American home with a main service panel and a ground rod. Let’s say you have a Sol-Ark 15k or an EG4 18k mounted next to your main panel, functionally similar units.
Now you install a ground mount array 150 feet away from your inverter, let’s call it a 10kw array.
Help me understand how the “ground wire” which in this instance is a “bonding conductor” will provide protection.
It isn’t there to protect against the DC voltage, it’s there to protect against AC voltage in the event of an equipment failure of the inverter, correct?
If the above is true, we’re now protecting against an inverter that has failed internally and is now sending out enough AC power to somehow energize the solar panels?
I’m not seeing where this supposed AC power is getting from the positive and negative wires on a solar panel to the frame itself? I’m not aware of a physical connection between them. Has anyone attempted to energize a solar panel with 120v? If not, I’ll give it a shot, I’ve got some older panels laying around.
Again I’m just trying to wrap my mind around how this current would actually flow. I suppose if you had the PV ground wire somehow bonded to the structure it becomes a theoretical possibility?
ksmithaz1
Solar / EV Junkie
It's there to protect you if some of the electricity you are generating somehow hits the frame because of a fault, or if the frame get's energized by lightning close by, or .... DC/AC not relevant. The circuit path is to the equipment at the other end of the DC cable. Both the frame and the equipment on the other end of the frame need to share the same ground, ie the same path to earth. That means a single point of entry to dirt is preferred or you create an alternate path which will create a potential in the middle. This is commonly already present at the main breaker panel. You can put it anywhere but you want only ONE tie point to dirt, everything should share it. In the case of a neutral on AC it helps trip breakers and detect ground faults, but the bottom line is a single tie point to your earth grounding.
Watts Happening
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Again I’m not against it, I’ll be bonding mine to my main panel. The arguments for needing it just seem rather unlikely. I’m sure there are more convincing ones, but personally the lightning one seems outlandish.
A ground array is by definition grounded, to what degree can be argued no doubt. But I’ve seen lightning bolts blow though 100 foot tall trees, they’re not exactly worried about conductivity. I also think it’s a bit foolish to think a 6-12awg conductor is somehow harnessing that power lol
ksmithaz1
Solar / EV Junkie
It's not "harnessing power." A direct lightning strike is going to take out everything. Lightning that hits your neighbors tree is going to create potential that radiates out unevenly. Everything that picks it up needs to dump it to the same ground. This is not really that complicated. If you create two paths to earth you can create a potential between them. The bond wire ensures there is not one.
Get a 100ft spool of wire run it to a ground rod 100ft away from your common. Read a small voltage between the grounds.