Grounding of off grid solar panels

[685eric]

I have a question about grounding my off the grid solar panels. My setup is for my cabin, 100% off the grid with a generator backup. Currently, I have my batteries, charge controller, and inverter all inside the cabin and they are all grounded to the main electrical panel. The main electrical panel is grounded with two ground rods in series, 6 ft apart. The only part of my system not yet ground is my solar panels. Currently is it 800 watts (~80-90v output) of solar panel which is about 50 feet from my cabin. I have 8/2 wire running from my panels inside to my charge controller, larger wire than needed but it wasn't much price difference to decrease my voltage drop.
Here are the options I was thinking about to ground my solar panels. They are listed from easiest to hardest.

1. Use the ground wire in the 8/2 wire to connect my solar panels to the main electrical panel ground, which is already ran into the cabin. I believe the ground wire would only be 10 gauge. (doubt this is large enough, but this is simple).
2. Add ground stakes in the ground at the solar panels. (I believe this would be bad because now I have two separate grounds for the system??)
3. Run an additional 6 gauge or larger ground wire from the solar panels to the main electrical panel ground. Would this and option 1 be bad because I am running a ground from my panels back into my cabin???

I really like option 2 but from what I read I think this would be a bad idea? Thoughts?

[Mike90250]

What you don't want to do, is create a "Gradient Ground" where lightning hits your panels & their ground rods and a high voltage is developed over the 50' to the cabin.

I don't know the proper code method to solve this, but it often includes heavy #4 or 6 solid ground wire connecting the grounds at the PV array to the grounds at the home, without directing a lightning strike into the interior of the house. If there was a lightning strike onto the array, you can expect all the solar gear, chargers, inverters, generators, to be fried. but the house should not catch fire.

This is different from grounding to provide a safety path to trip a circuit breaker in case of an overload. The 2 methods must mesh together to provide protection.

https://en.wikipedia.org/wiki/Earth_potential_rise

[bcroe]

You certainly do not want a gradient ground within a building. Between buildings is a different
consideration, hopefully few people are out there in a storm. My array has 60 steel reinforced
concrete posts grounding the framework, many structures have multiple grounding in their structure.
Bruce Roe

[685eric]

What you don't want to do, is create a "Gradient Ground" where lightning hits your panels & their ground rods and a high voltage is developed over the 50' to the cabin.

I don't know the proper code method to solve this, but it often includes heavy #4 or 6 solid ground wire connecting the grounds at the PV array to the grounds at the home, without directing a lightning strike into the interior of the house. If there was a lightning strike onto the array, you can expect all the solar gear, chargers, inverters, generators, to be fried. but the house should not catch fire.

This is different from grounding to provide a safety path to trip a circuit breaker in case of an overload. The 2 methods must mesh together to provide protection.

https://en.wikipedia.org/wiki/Earth_potential_rise

When you say "wire connecting the grounds at the PV array to the grounds at the home, without directing a lightning strike into the interior of the house" how exactly is this achieved. If I go with the single ground (option 3), the lightning strike would travel back into the house. Not sure how I can stop both? Seems like the best option is to not ground the panels at all.

[685eric]

You certainly do not want a gradient ground within a building. Between buildings is a different
consideration, hopefully few people are out there in a storm. My array has 60 steel reinforced
concrete posts grounding the framework, many structures have multiple grounding in their structure.
Bruce Roe

So would you technically have the potential for a "Gradient Ground" due to all the posts?

[bcroe]

My understanding, there could be a lot of strike potential between my array and my house,
but I do not care. Perhaps best would be a ground where solar enters a building, then the
other stuff in the house is connected via another lead/net to that ground, so strike current
is not flowing through the building net. Any strike current through the building will tend to
cause big voltages between things connected by the net.

I am far from the expert, so people like SunKing might want to make suggestions. My solar
is 500 feet from the house. It feels like, the better grounding at the array, the less voltage
will head for the house. Bruce Roe

[NewBostonConst]

I personally would use option one with a ground rod at the solar panels to connect any equipment grounds you have to run back to the house. You might not have any.

I would also sink another ground rod for lightening and connect the panel frames and the mounting hardware to it.

Thus you have a circuit ground path tied to the main house panel and a lightening ground path. This would follow 90% of the code but also makes me feel the safest. Who wants a path to lead a lightening strike or high voltage into your house. It is my opinion and I am not telling you what to do.

You also have to look at your location. Are your panels the highest thing? If not they are likely safe. If the solar panels are the highest thing with nothing else around I would add a lightening rod.

Here is some wire sizes for the lightening rod I pulled off another site ES grounding solutions:

• Class I - Copper: Minimum Gauge is 2 AWG, with a minimum individual strand size of 17 AWG.
• Class II - Copper: Minimum Gauge is 00 AWG, with a minimum individual strand size of 17 AWG.

• Class I - Aluminum: Minimum Gauge is 0 AWG, with a minimum individual strand size of 14 AWG.
• Class II - Aluminum: Minimum Gauge is 0000 AWG, with a minimum individual strand size of 14 AWG.

Good luck.

[HoodOffGrid]

I personally would use option one with a ground rod at the solar panels to connect any equipment grounds you have to run back to the house. You might not have any.

I would also sink another ground rod for lightening and connect the panel frames and the mounting hardware to it.[/LIST]Good luck.

I have a similar situation as I want to document on video my process on grounding my solar system array but did not find the best material out there to show how to "properly" ground a solar array. I was talking to a Home Depot associate who deals with a radio antenna, and he advised that he had a 60-foot tower that got struck by lightning and he had a coax cable from the structure inside of the house and it blew a hole in his desk.

I would like to tie my system to the grounding rod that is already outside of my home as it shows that if you use more than one grounding rod, you may cause issues, also it would be against NEC code as the rods must be six feet apart and the other one unused/buried. I would not want to run the ground inside the of the house to my electronics because I would not want them to be fried in a lightning strike.

I would like to follow the NEC code, as I do not want to be in a position to "break code" or do something that would be dangerous.

[NewBostonConst]

Don't see why you would have a problem with more then one grounding rod.

1. The grounding rods must be more then 6 feet apart when more then one is required by code. Thus for the second one to count it must be 6 foot away from the first in NEC.
2. If your house has multiple circuit breaker boxes(aka sub panels) you will likely have multiple grounding rods. I have 3 sub panels at my current house and 6 ground rods.
3. You might be confusing bonding with grounding, you can only connect the ground to the neutral in one place and have to run a separate ground and neutral wire after that connection, but can connect the ground to a grounding rod when ever you want. Most electricians only put in what is needed.
4. They are easy to install and provide a place for excess electricity go....more is better in this case.

[Mike90250]

There is electrical ground in your service panel, and there are equipment grounds - like PV racks and arrays.

One is for shock prevention and other is to prevent lightning from entering your home

If you search on You Tube for " mike holt grounding and bonding " he is a author for some sections of the NEC and has many presentations on this confusing issue.

http://www.mikeholt.com/img/mojonews/GroundBondPoster001-300-dpi.jpg

GroundBondPoster001-300-dpi.jpg

[HoodOffGrid]

Don't see why you would have a problem with more then one grounding rod.

1. The grounding rods must be more then 6 feet apart when more then one is required by code. Thus for the second one to count it must be 6 foot away from the first in NEC.
2. If your house has multiple circuit breaker boxes(aka sub panels) you will likely have multiple grounding rods. I have 3 sub panels at my current house and 6 ground rods.
3. You might be confusing bonding with grounding, you can only connect the ground to the neutral in one place and have to run a separate ground and neutral wire after that connection, but can connect the ground to a grounding rod when ever you want. Most electricians only put in what is needed.
4. They are easy to install and provide a place for excess electricity go....more is better in this case.

Yes, it seems that there is difference be grounding and bonding. Learned something new.

[HoodOffGrid]

There is electrical ground in your service panel, and there are equipment grounds - like PV racks and arrays.

One is for shock prevention and other is to prevent lightning from entering your home

If you search on You Tube for " mike holt grounding and bonding " he is a author for some sections of the NEC and has many presentations on this confusing issue.

http://www.mikeholt.com/img/mojonews/GroundBondPoster001-300-dpi.jpg

GroundBondPoster001-300-dpi.jpg

Will definitely check this out, thanks.