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How to properly ground off grid solar system

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Goats

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Aug 7, 2020
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I’ve got a pretty basic off grid solar system. I’m trying to get it grounded correctly but I keep getting confused by ground loops and can’t find any videos that covers this topic on a complete system. Perhaps someone can help guide me here.

My system is as such:

Roof of aluminum sunroom> 2x 330w 37.8v solar panels in series > inside the sun room > charge controller > 100 ah 24v batteries on BMS > Busbars > 24v 2000w ac inverter.

Nothing is currently grounded. Even the solar panels are isolated with VHB tape. The charge controller, inverter battery and busbars are in a wood box.
For code reasons, I am in Tampa Florida.

There is a 1p breaker on each component

Equipment:
Panels
Inverter
Charge controller
Battery
 
iceledoar said:
the panels need to be bonded to a ground, which needs to be a separate ground form the house. Without knowing about what your powering with the inverter, unable to provide further advice.
Click to expand...
It’s just being used as backup power but mostly just tinkering and learning experiment. I don’t have anything planned. If there’s a power outage, maybe a fan, tv and light.
 
Last edited:
I'm a little confused where you used the tape. Is it to isolate the racking from the metal roof, or the panels from the racking? Without knowing a bit more about your specific system, I can just make generalizations based on NEC requirements.

The metal panel frames and rails need to be bonded together. This is generally done by the clamps that connect the panels to the rails. If not, then you need to get something like a Burndy Lay-in-lug to attach to each panel and rail. They are then connected together with #6 uninsulated copper wire, that should go to a grounding rod. A grounding wire should come from this whole setup down to your indoor equipment. Being installed on a dwelling, you are required to have ground fault protection (GFP). So you should have a ground fault protector like the Midnite Solar MNDC-GFP63 between the panels and the charge controller. This device is connected to both ground and negative, and it is in there and only there that negative and ground are bonded together. If you do not use a GFP, then you should find one location in your setup where you wire a connection from ground to negative to bond them. Again, only do that if none of your equipment has built-in GFP (your charge controller does not, other brands do).

I couldn't tell if the inverter you have has a ground lug on it. If so, it should also be connected to the ground.
 
SolarQueen said:
I'm a little confused where you used the tape. Is it to isolate the racking from the metal roof, or the panels from the racking? Without knowing a bit more about your specific system, I can just make generalizations based on NEC requirements.

The metal panel frames and rails need to be bonded together. This is generally done by the clamps that connect the panels to the rails. If not, then you need to get something like a Burndy Lay-in-lug to attach to each panel and rail. They are then connected together with #6 uninsulated copper wire, that should go to a grounding rod. A grounding wire should come from this whole setup down to your indoor equipment. Being installed on a dwelling, you are required to have ground fault protection (GFP). So you should have a ground fault protector like the Midnite Solar MNDC-GFP63 between the panels and the charge controller. This device is connected to both ground and negative, and it is in there and only there that negative and ground are bonded together. If you do not use a GFP, then you should find one location in your setup where you wire a connection from ground to negative to bond them. Again, only do that if none of your equipment has built-in GFP (your charge controller does not, other brands do).

I couldn't tell if the inverter you have has a ground lug on it. If so, it should also be connected to the ground.
Click to expand...
Thank you. The panels are on z brackets, not rails. The tape is there being used as a water seal and addition strength because I don’t trust self tapping screws alone. The charge controller does have a ground lug. I’m a bit concerned about the GFP you recommended since I can’t find any rated for the 600+ volts of the PV array.
 
Goats said:
I’m a bit concerned about the GFP you recommended since I can’t find any rated for the 600+ volts of the PV array.
Click to expand...
You have " 2x 330w 37.8v solar panels in series", that is 75V, well under the 150V of the GFP. The 600V rating you see is the maximum you can wire them in series, so if you had 15 in series, which you don't. Your charge controller is only rated 100V.

Use 2 lay-in-lugs for your panels, don't worry about the Z feet.
 
SolarQueen said:
You have " 2x 330w 37.8v solar panels in series", that is 75V, well under the 150V of the GFP. The 600V rating you see is the maximum you can wire them in series, so if you had 15 in series, which you don't. Your charge controller is only rated 100V.

Use 2 lay-in-lugs for your panels, don't worry about the Z feet.
Click to expand...
I’m dumb. I was thinking about watts.

Thank you. I think I’m starting to get a mental picture. Theres so many system diagrams but no one ever talks about ground. Do you happen to know any diagrams so I can really visualize this? Thank you again.
 
Goats said:
Thank you. I think I’m starting to get a mental picture. Theres so many system diagrams but no one ever talks about ground. Do you happen to know any diagrams so I can really visualize this? Thank you again.
Click to expand...
There's a reason no one draws ground in their schematics. We all hate drawing ground. ;) Here's an old drawing with a bigger system than what you've got, hopefully it clears it up more than it confuses.
https://imgur.com/jidYsXJ
 
SolarQueen said:
There's a reason no one draws ground in their schematics. We all hate drawing ground. ;) Here's an old drawing with a bigger system than what you've got, hopefully it clears it up more than it confuses.
Click to expand...
Unfortunately your system is significantly more complex than mine and just added to my confusion.
 
SolarQueen said:
I'm a little confused where you used the tape. Is it to isolate the racking from the metal roof, or the panels from the racking? Without knowing a bit more about your specific system, I can just make generalizations based on NEC requirements.

The metal panel frames and rails need to be bonded together. This is generally done by the clamps that connect the panels to the rails. If not, then you need to get something like a Burndy Lay-in-lug to attach to each panel and rail. They are then connected together with #6 uninsulated copper wire, that should go to a grounding rod. A grounding wire should come from this whole setup down to your indoor equipment. Being installed on a dwelling, you are required to have ground fault protection (GFP). So you should have a ground fault protector like the Midnite Solar MNDC-GFP63 between the panels and the charge controller. This device is connected to both ground and negative, and it is in there and only there that negative and ground are bonded together. If you do not use a GFP, then you should find one location in your setup where you wire a connection from ground to negative to bond them. Again, only do that if none of your equipment has built-in GFP (your charge controller does not, other brands do).

I couldn't tell if the inverter you have has a ground lug on it. If so, it should also be connected to the ground.
Click to expand...
After sleeping on it, I think I have a better idea. I just ordered everything you recommended. My only questions, in your photo your PV goes directly to ground rod and splits back inside to your internal equipment. Is this advised?

Additionally, you inverter appears ungrounded. Why’s that?
 
The ground is continuous from the grounding rod, to the rails, to the bus bars, to the breakers, to the charge controller, etc. It is bringing all of the ground to the same potential. You caught me on the inverter, I think this model I drew it for had a plastic body, so no ground. If yours has a grounding lug, put it on.
 
SolarQueen said:
The ground is continuous from the grounding rod, to the rails, to the bus bars, to the breakers, to the charge controller, etc. It is bringing all of the ground to the same potential. You caught me on the inverter, I think this model I drew it for had a plastic body, so no ground. If yours has a grounding lug, put it on.
Click to expand...
Ok so just to be clear. I should not go from my panels to ground but instead go from my panels to my busbar and everything should be bonded to that busbar. I should only have one ground leading to the grounding rod?
 
I have a flow up question to one above. Does it matter where the grounding rod connects in? Can I bring it in to the A/C load center and bond it to to neutral? Of course assuming all components in the system are bonded., A/C and D/C). In my application I have PV panels bolted to a steel roof. I'm not sure if that changes the picture/
 
SolarQueen said:
The ground is continuous from the grounding rod, to the rails, to the bus bars, to the breakers, to the charge controller, etc. It is bringing all of the ground to the same potential. You caught me on the inverter, I think this model I drew it for had a plastic body, so no ground. If yours has a grounding lug, put it on.
Click to expand...
Wouldn't the inverter be grounded on the negative line that is connected to the bus tgT the ground is connected to?

That's actually a question I have that I thought you answered with thY schematic.

If I ground the negative bus bar, is everything connected to the bus bar grounded now or do I have to run individual lines to each component on the bus bar?
 
I have two separate groundings. My panels are connected to a pair of 8' copper rods, 8' apart.
My inverters are grounded with a separate set of 8' ground rods, 8' apart.
All the information I have found is why I have two separate groundings.

The mention of connecting a ground to neutral opens up another can of worms. Can you really trust a relay in your inverter to connect, or disconnect the Neutral ground connection.

Grounding is very important, as I would rather work with 440vac, than 48vdc. DC is dangerous.
 
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