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Ground mount panels grounding questions.

timselectric said:
One EGC per group of circuit carrying conductors, in a cable, raceway, or conduit.
Click to expand...
Ok, so if you ran multiple conduits, you would need multiple EGC, one for each conduit, even if they all originated at the same place and are going to the same place, in the same trench.

I guess that makes sense, in case a conduit was damaged somehow, there would still be an EGC running with the remaining one.
 
cs1234 said:
Ok, so if you ran multiple conduits, you would need multiple EGC, one for each conduit, even if they all originated at the same place and are going to the same place, in the same trench.

I guess that makes sense, in case a conduit was damaged somehow, there would still be an EGC running with the remaining one.
Click to expand...
Correct
 
ScropusGobbleBottom said:
Is there any problem using bare wire?
Click to expand...
It meets code. (In most cases)
But it's hard to keep it from touching anything along the way.
I don't use or recommend bare for anything other than equipotential bonding around a swimming pool.
And most bare conductors at the local hardware stores are solid #8 and harder to work with.
 
Are we allowed to use coated 10awg copper for panel frames and such, just running from panel to panel with no protective conduit? It doesn't need to be fat 6awg aluminum or something?
 
cs1234 said:
Are we allowed to use coated 10awg copper for panel frames and such, just running from panel to panel with no protective conduit? It doesn't need to be fat 6awg aluminum or something?
Click to expand...
If exposed to physical damage (Not in conduit), the minimum size required is #6.
And yes green insulated stranded copper, is what I use and recommend.
 
timselectric said:
minimum size required is #6.
Click to expand...
I guess I need to redo mine since I used 12 awg bare.

So I am not using regular solar rails. They are bolted to unistrut. So that means I need to ground each panel?

What is an easy way to remove insulation on 2 inches in the middle of a wire??
 
cs1234 said:
@timselectric

Does the wire have to be continuous from panel to panel, or can you use separate pieces of wire to go from each one if necessary / the grounding lug allows?
Click to expand...
NEC states that the grounding must not be broken by removing one. So I would bet that is not going to fly.
I am interested in what Tim has to say on this.

Thank you Tim. You are a wonderful resource for us plebs.
 
cs1234 said:
@timselectric

Does the wire have to be continuous from panel to panel, or can you use separate pieces of wire to go from each one if necessary / the grounding lug allows?
Click to expand...
Basically this.
ScropusGobbleBottom said:
NEC states that the grounding must not be broken by removing one. So I would bet that is not going to fly.
Click to expand...
It doesn't necessarily have to be unbroken.
But the loss of one connection to a panel can't remove grounding of the rest.

So, while you can't connect seperate pieces from panel to panel in a daisy chain.
You can run a main grounding conductor and tap a separate piece from it to each panel.
 
My inverters/system is grounded to the same ground rod as the main panel. (The ground rod for the house)

For the solar mount frame (EG4 Brightmount - the rails are bonded), I was planning to drive a ground rod just so there are no accidental shocks when touching it, and also for lightning.

Do I drive a ground rod for each mount, or can I use multiple clamps on one ground rod? I will have 4 arrays total, so 4 mounts.
 
Travis55 said:
For the solar mount frame (EG4 Brightmount - the rails are bonded),
Click to expand...
To what?
Travis55 said:
I was planning to drive a ground rod just so there are no accidental shocks when touching it, and also for lightning.
Click to expand...
A ground rod does nothing to prevent getting shocked.
An EGC connecting it to the grounding system and the N/G bond, does.
Travis55 said:
Do I drive a ground rod for each mount, or can I use multiple clamps on one ground rod? I will have 4 arrays total, so 4 mounts.
Click to expand...
None of the above.
 
timselectric said:
To what?

A ground rod does nothing to prevent getting shocked.
An EGC connecting it to the grounding system and the N/G bond, does.

None of the above.
Click to expand...
I'm not sure I understand - The inverters (and by extension battery bank and solar panels since they are connected to the inverter) are grounded at the N+G Bond at service entrance (transfer switch in my case, this is the same ground that the main panel in the home uses).

The rack frame itself needs grounding per the manual. I was planning to drive a ground rod and run 6 awg copper from the rack frames grounding lug, to a ground rod that I was going to drive nearby.

The ground mount is about 100ft away from the house for reference if that matters
 
Last edited:
Travis55 said:
The rack frame itself needs grounding per the manual.
Click to expand...
According to this, it is already grounded. 👇

Travis55 said:
The inverters (and by extension battery bank and solar panels since they are connected to the inverter) are grounded at the N+G Bond at service entrance (transfer switch in my case, this is the same ground that the main panel in the home uses).
Click to expand...

Travis55 said:
I was planning to drive a ground rod and run 6 awg copper from the rack frames grounding lug, to a ground rod that I was going to drive nearby.
Click to expand...
This would be an auxiliary ground rod.
Auxiliary ground rods are not required or recommend.
They only increase the risk of equipment damage from the gradient pulse created by a nearby lightning strike.
 
timselectric said:
According to this, it is already grounded. 👇




This would be an auxiliary ground rod.
Auxiliary ground rods are not required or recommend.
They only increase the risk of equipment damage from the gradient pulse created by a nearby lightning strike.
Click to expand...
Well shoot, I'm pretty confused now. I thought there was a difference between grounding the panels themselves, and the mount/rack.

The panels have a positive and negative string coming off of them in series if I understand correctly. The positive and negative string feeds back to the inverter and plugs in there as PV input. The inverter is grounded through the AC Output terminals ground, which runs to the bonded service entry ground, so that would technically mean they are grounded as long as the inverter is grounded?

Here's the manual page about grounding the rack:

1719677459153.png
 
doox00 said:
So it gets grounded to ac side ground? Was not sure if the DC and AC side were completely separated. Thanks for the info.
Click to expand...

I would ground (bond) PV frames to the DC side, at the SCC or inverter.

Not directly to the AC breaker panel or ground rod, because I don't want DC current from a fault going there first, then going back through AC ground wire to reach SCC. If an electrician disconnected the AC circuit (with power off) he would be surprised when it pulled a DC arc.

timselectric said:
This serves no purpose. As you still need the EGC ran back to the existing grounding system for protection.
And if an auxiliary ground rod (this is what it would be) is installed, it must also be connected to the existing grounding system, to make it also safe.
Click to expand...

Yes. Connect at DC hardware, I say.

timselectric said:
Everywhere you run circuit conductors, an EGC should be ran with them.
Click to expand...

Exactly.
If there is a PV DC fault to frame, the ground bonding wire carrying fault current should be routed together with the PV wires, completing a circuit without having a big loop or going through the wires of some other circuit.

At the array, often single wires so those have space between them.
If routed to avoid that, might be better at avoiding pickup of RF interference and coupled lightning surge.

timselectric said:
All EGC's should be bonded (connected) together at every location. Along with all equipment, enclosures, boxes, raceways, and framing.
Click to expand...

And use wire to stitch everything together. Don't use chassis as part of the ground path for faults to any other hardware, only for faults to that chassis.

Exception being when PV mounting rails are used as ground conductors.

doox00 said:
Can I run the ground from the arrays in the same conduit as the pv wire that goes to the inverters?
Click to expand...

Yes. Required according to my understanding of NEC.

And this means bond the wire at SCC or inverter chassis. Not at AC breaker panel or at ground rod.

ScropusGobbleBottom said:
NEC states that the grounding must not be broken by removing one. So I would bet that is not going to fly.
I am interested in what Tim has to say on this.
Click to expand...

Lay-in lugs. Lets you remove and unhook a panel without interrupting ground wire to rest of them.

1719678678323.png

Alternatively, some panel clamps, also WEEB washers, provide bonding of panel frame to rails.
Looking through SolarAPP+ I discovered REC panels were listed for bonding with Unirac clamps, but NE Solar were not.

doox00 said:
I am using 10 gauge pv wire for the arrays, which type and gauge should I be using for the grounding?
Click to expand...

timselectric said:
Assuming that your PV panel stickers say 15a maximum fuse size.
EGC should be a minimum of #14 AWG copper.
I would recommend (green) insulated THHN/THWN-2.
Click to expand...

Although it might seem silly, my new install with 4x 10A PV strings wired 12 awg will have 4 awg ground wire.

In part because I have it (from 200A service upgrade, where 6 awg would be sufficient except code requires 4 awg to water pipe.) But also:

Consider 10A Isc x 1.56 x 4 parallel strings all shorted = 62.4 A ampacity required for continuous use.

timselectric said:
View attachment 225262
Click to expand...

I would say do not use this table for ground conductors of PV, which don't trip breakers.
Continuous current, so use this one:


1719679040568.png
I could have 4x PV+ + 1x Ground carrying current, so derate to 80%.
Looks like 4 awg is just about right.

1719679108071.png
 
Travis55 said:
Well shoot, I'm pretty confused now. I thought there was a difference between grounding the panels themselves, and the mount/rack.

The panels have a positive and negative string coming off of them in series if I understand correctly. The positive and negative string feeds back to the inverter and plugs in there as PV input. The inverter is grounded through the AC Output terminals ground, which runs to the bonded service entry ground, so that would technically mean they are grounded as long as the inverter is grounded?

Here's the manual page about grounding the rack:

View attachment 225437
Click to expand...
No, they are not already grounded.
You have to run an EGC (Equipment Grounding Conductor) from the panel frames and racking back to the grounding system to ground/ Bond them.
Which is what I thought that you had done, when you said that they were grounded by extension from the inverter.
 
Hedges said:
Although it might seem silly, my new install with 4x 10A PV strings wired 12 awg will have 4 awg ground wire.
Click to expand...
It's quite a bit of overkill. But Larger is fine, the required size is a minimum requirement.
Hedges said:
I would say do not use this table for ground conductors of PV, which don't trip breakers.
Continuous current, so use this one:
Click to expand...
That table is for current carrying conductors, not EGC's.
Current carrying conductors have to be rated for full current continuously without overheating.
EGC's are only rated for instantaneous fault current, which only lasts for a second.
This is why they can be much smaller.
 
Hedges said:
I would ground (bond) PV frames to the DC side, at the SCC or inverter.

Not directly to the AC breaker panel or ground rod, because I don't want DC current from a fault going there first, then going back through AC ground wire to reach SCC. If an electrician disconnected the AC circuit (with power off) he would be surprised when it pulled a DC arc.



Yes. Connect at DC hardware, I say.



Exactly.
If there is a PV DC fault to frame, the ground bonding wire carrying fault current should be routed together with the PV wires, completing a circuit without having a big loop or going through the wires of some other circuit.

At the array, often single wires so those have space between them.
If routed to avoid that, might be better at avoiding pickup of RF interference and coupled lightning surge.



And use wire to stitch everything together. Don't use chassis as part of the ground path for faults to any other hardware, only for faults to that chassis.

Exception being when PV mounting rails are used as ground conductors.



Yes. Required according to my understanding of NEC.

And this means bond the wire at SCC or inverter chassis. Not at AC breaker panel or at ground rod.



Lay-in lugs. Lets you remove and unhook a panel without interrupting ground wire to rest of them.



Alternatively, some panel clamps, also WEEB washers, provide bonding of panel frame to rails.
Looking through SolarAPP+ I discovered REC panels were listed for bonding with Unirac clamps, but NE Solar were not.





Although it might seem silly, my new install with 4x 10A PV strings wired 12 awg will have 4 awg ground wire.

In part because I have it (from 200A service upgrade, where 6 awg would be sufficient except code requires 4 awg to water pipe.) But also:

Consider 10A Isc x 1.56 x 4 parallel strings all shorted = 62.4 A ampacity required for continuous use.



I would say do not use this table for ground conductors of PV, which don't trip breakers.
Continuous current, so use this one:



I could have 4x PV+ + 1x Ground carrying current, so derate to 80%.
Looks like 4 awg is just about right.
Click to expand...

Thanks for all the useful info, what does SCC stand for though?

And thanks everyone, super helpful info here!
 
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