PV Array Grounding Options

bookish

New Member
I have questions about grounding the PV array I'm doing. I'm so glad this forum is here for questions like these where hours of internet searching leave me drawing a blank, or exhausted.

The site is remote and 9 hours from my house, so I'm planning each trip carefully. I've sunk posts for the ground mount for 9, 250 W Santan panels in 3 S 3 P configuration.

On my next trip I'll build the ground mount from wood, and attach and wire the array. The panels are on a pallet in my truck and without cutting the straps I can tell they have plastic frames. I have Z-brackets for mounting them to the wood frame.

Q1: Since the panels are plastic-framed, and the mount is wood, I guess there is no need to link the PV panels together for grounding. Is this correct?

On the mount I'll install a Midnite Solar combiner box ( MNPV6 ) with 3, 15 A breakers, and a 300 V DC SPD (Midnite Solar ). I *think* this is an okay setup so far. Tell me if I'm wrong.

Then I have a #2 solid Cu ground wire sticking out of the foundation just outside of the brick wall forming the side of the shop that will be the battery house. There is ~8 feet between the combiner box and the shop wall with the ground wire. I intend to put metal (?) conduit underground between them, then run it up the outside of the brick wall and over the wall and under the roof to the service panel inside. (Prefer not to remove or drill bricks.)

Q2: Is it a good idea to run to ground from the combiner box through the conduit all the way to the brick wall and then split off and run over to the ground wire? Or go with USE2, in its own conduit from the box to surface grade, then USE2 alone underground to the ground wire?

Or should I keep the grounding wire in conduit all the way inside to the service panel and ground all the components together to that outside #2 Cu ground (by drilling thru the brick -- it'll have to come to that eventually.). From what I understand I do want to ground all parts of the system to the same ground wire.
 

FilterGuy

What, me worry?
Q1: Since the panels are plastic-framed, and the mount is wood, I guess there is no need to link the PV panels together for grounding. Is this correct?
If there is no exposed metal, and the frame is wood, there isn't anything to ground.
On the mount I'll install a Midnite Solar combiner box ( MNPV6 ) with 3, 15 A breakers, and a 300 V DC SPD (Midnite Solar ). I *think* this is an okay setup so far. Tell me if I'm wrong.
The surge protector will need a ground and you should ground the metal combiner box so plan on running a ground wire along with the plus and minus.
Q2: Is it a good idea to run to ground from the combiner box through the conduit all the way to the brick wall and then split off and run over to the ground wire? Or go with USE2, in its own conduit from the box to surface grade, then USE2 alone underground to the ground wire?

Or should I keep the grounding wire in conduit all the way inside to the service panel and ground all the components together to that outside #2 Cu ground (by drilling thru the brick -- it'll have to come to that eventually.). From what I understand I do want to ground all parts of the system to the same ground wire.
You are absolutely correct that you want to tie everything to the same ground rod(s) at *one* point.

I would run the conduit with all 3 wires to a box on the outside wall. In side the box, the Ground would go into a 3 Wire crimp connector:
1) Ground wire from the combiner box
2) Grounding electrode Conductor to the Grounding Electrode
3) Ground Wire into the building and to the common grounding bus bar.

(The reason for the crimp connector and not a wire nut is that the NEC requires any splice to be with a permanent connection.)

From the box, I would go ahead and drill through the brick to go into the house with the ground and two power wires. This is for a few reasons:
  • Shorter is always better from an efficiency point of view.
  • They say to avoid sharp bends on grounding wires.
  • Running conduit up and over the wall will be a PITA.
 

bookish

New Member
If there is no exposed metal, and the frame is wood, there isn't anything to ground.

The surge protector will need a ground and you should ground the metal combiner box so plan on running a ground wire along with the plus and minus.

You are absolutely correct that you want to tie everything to the same ground rod(s) at *one* point.

I would run the conduit with all 3 wires to a box on the outside wall. In side the box, the Ground would go into a 3 Wire crimp connector:
1) Ground wire from the combiner box
2) Grounding electrode Conductor to the Grounding Electrode
3) Ground Wire into the building and to the common grounding bus bar.

(The reason for the crimp connector and not a wire nut is that the NEC requires any splice to be with a permanent connection.)

From the box, I would go ahead and drill through the brick to go into the house with the ground and two power wires. This is for a few reasons:
  • Shorter is always better from an efficiency point of view.
  • They say to avoid sharp bends on grounding wires.
  • Running conduit up and over the wall will be a PITA.
Thanks, this is very helpful. Turns out the panel frames are Al after all - being black they seemed like plastic. So I'll ground them together.

A guy looking at my Cu wire going onto the concrete footing said my ground point should be in earth, not concrete. Is he right?
 

FilterGuy

What, me worry?
A guy looking at my Cu wire going onto the concrete footing said my ground point should be in earth, not concrete. Is he right?
Not necissarily.

If the wire is bonded with the rebar in the concreete it may be a sufficient ground. (It is on many buildings)
 

chrisski

Solar Addict
Do you know the standard grounding in the area?

I used to think a copper bar into the ground was the only way, but in some places grounding to bars in the concrete frame is code. Has to do with soil being too dry.
 
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