Solo ground from Solar meter to sub panel, What size?

Status
Not open for further replies.

JoeNorm

Senior Member
Location
WA
Hello all,

We recently completed a Solar array on a detached garage and landed the feed in the main panel of the house. The inspector says we must attach the ground to the grounding system of the structure we have the solar array on. And he is right after reading 690.47

So now I just have to run a single ground from our meter to the sub in the garage. The walls are open so no big deal but I was wondering if there are rules for running solo grounds and if they have to be a certain size regardless of what is required. In this case I need a #10 ground. Can I run any #10 ground I have through the studs(they will be covered with sheet rock).

Thanks and any code reference appreciated.
 
Hello all,

We recently completed a Solar array on a detached garage and landed the feed in the main panel of the house. The inspector says we must attach the ground to the grounding system of the structure we have the solar array on. And he is right after reading 690.47

So now I just have to run a single ground from our meter to the sub in the garage. The walls are open so no big deal but I was wondering if there are rules for running solo grounds and if they have to be a certain size regardless of what is required. In this case I need a #10 ground. Can I run any #10 ground I have through the studs(they will be covered with sheet rock).

Thanks and any code reference appreciated.

Perhaps some more details would be prudent:

1. Where is the inverter?
2. To clarify, the garage has a feeder and subpanel, but the Pv connects to the house panel?
3. When you say "....single ground from our meter to the sub in the garage." what is "our meter"?
 

JoeNorm

Senior Member
Location
WA
Inverters are with each panel, SunPower micro-inverters with "integrated" ground

Yes, we put the array on the garage but ran the Inverter output (in this case from a combiner panel and production meter) through a conduit to the main panel of the main house, which is only about 30 feet from the garage. We did this in anticipation for a future battery system.

So the situation looks specifically like this: PV and Inverters on the roof of garage, Combiner panel and Production meter on north wall of garage. From there the underground conduit takes the combined inverter output to the main panel of house (separate building).

Inspector says I need to land a ground for the PV array within the grounding system in which the PV array is connected to (690.47), in this case the sub panel in the garage which is located on the West wall of garage. Walls are all still open framing so this will be easy.

I was going to run a ground wire from our combiner panel/production meter, through the wall, and connect to the ground bar of the sub panel.

From my understanding this is still an equipment ground(correct me if I am wrong) in which case it can be #10 copper. Can I run say, #10 THHWN ground through the wall? Is there a minimum size I can by itself in a wall? Does it have to be a specific type of wire (bare vs something else?)

thanks
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Which code cycle are you on? 690.47 has changed a lot in each of the last several code cycles. Some code cycles will be more specific in addressing this.

Regardless, I tend to think the ground wire the inspector is asking for is either a grounding electrode conductor or perhaps a bonding jumper. Your original post referred to a "ground to the grounding system of the structure." If that's the language the inspector used it sure sounds like a GEC. (And it sounds like he asked that it go to the electrode and not necessarily the existing subpanel, although if the sub groundbar is where the existing GEC terminates then perhaps it makes not much difference.)

It is not an EGC because the purpose is to provide a local connection to earth, not to carry fault current. Your equipment grounding conductor (for fault current) should have been run with your circuit conductors, i.e. back to the house. EGCs are only allowed to be run separately from circuit conductors under certain exceptions and this is not one of them.
 
Last edited:

JoeNorm

Senior Member
Location
WA
Thank you, what you're saying all makes sense, and my guess is the inspector did want a GEC. But Why? We have essentially done away with them for our installs a couple years ago. With Sunpower ALL grounding is taken care of with the #12 ground within their proprietary cable, much like Enphase I think.

So typically we do not run anything resembling a GEC off the roof, so why would they want one now just because we're on a separate structure.

I'm not arguing anything, just very curious and have never fully had a grasp on the GEC/EGC distinction in solar.

thanks
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
You know what...to answer your original question...

Just run 6awg bare copper.

You still didn't tell us your code cycle, but regardless of whether it is a GEC, as we'd probably say under the 2014 NEC, or an EGC or equipment bonding jumper, as under the 2017 NEC, the answer is still going to be 6awg. That's because if a GEC it's going to be under 250.64(B), and if a bonding jumper then 250.120(C). And both of those sections prohibit running an exposed, unprotected wire smaller than 6awg. There's a fair number of other code sections that will harken back to those, they are pretty established.

As far as the why...
In the 2017 the code making panel got rid of most of the overzealous PV grounding requirements. (Finally!) But they still left it at a) there has to be an grounding electrode system at the structure with the PV and b) the PV array has to be connected to it. So that's what your inspector is looking at. If you had tied into the garage subpanel and landed your ground there, it would already be connected and you'd already be done. Your separate circuit is what's different in this case.
 
Status
Not open for further replies.
Top