NEC 690.47(A)

[BarklieEstes]

Good afternoon,

Does 690.47(A) require bringing detached structure grounding electrode system up to code when installing a solar system on it?

The situation at hand is a PV system installed on a boat dock roof that is connected to a boathouse subpanel (no electrode at the subpanel) that is fed by a 4-wire feeder from a single-family dwelling that has an existing grounding electrode system compliant with Article 250 Part III.

My perspective is that the PV system 1) is connected to associated distribution equipment connected to a ground electrode system, 2) the support structure utilizes an Article 250 Part III grounding electrode system (the one at the house), and 3) the PV array equipment grounding conductors are connected to that system in accordance with Part VII of Article 250.

I see that a 250.32(A) violation already exists. I don't see where Part II of Article 250 gets invoked or how a not-solidly grounded PV system contributes to that violation. In code terms, my argument would be that "the existing building is no less conforming to the provisions of the VCC than the existing building or structure was prior to the alteration."

Regards,
Barklie

 

[wwhitney]

The first sentence of 2020 NEC 690.47(A) is "A building or structure(s) supporting a PV system shall utilize a grounding electrode system installed in accordance with Part III of Article 250." So that applies to your boat dock/shed structure, it is supporting a PV system. So your boat dock/shed structure needs a GES installed in accordance with Part III of Article 250.

I.e. The existing 250.32(A) violation becomes a 690.47(A) violation if you put PV on the building.

No opinion on the technical merits of the situation, just interpreting the NEC as written.

Cheers, Wayne

 

[BarklieEstes]

Wayne,

Thanks for the quick response. Are you saying that the boat house does not "utilize" the home's GES? It seems like that would be its only connection to ground.

Assuming your answer is no, could I bang a 3/4" pipe 8' deep at the boat house? The inspector is wanting me to run the GEC all the way back to dry land.

Regards,
Barklie

 

[wwhitney]

Thanks for the quick response. Are you saying that the boat house does not "utilize" the home's GES?

It does indirectly, but that GES is not "installed in accordance with Part III of Article 250" with respect to the boathouse. See 250.50. It says all electrodes present "at" the building shall be connected to form the GES, and if no electrodes exist, one or more shall be installed and used.

Cheers, Wayne

 

[BarklieEstes]

I see your path there.

Could I bang a 3/4" pipe 8' deep at the boat house? The inspector is wanting me to run the GEC all the way back to dry land.

Regards,
Barklie

 

[wwhitney]

Could I bang a 3/4" pipe 8' deep at the boat house? The inspector is wanting me to run the GEC all the way back to dry land.

Not something I've thought about, but I don't see why a ground rod or pipe electrode couldn't be installed underwater, as long as you have 8' of length in contact with the soil (250.53(G)). Also, you would need two of them, just like with ground rods. [More properly, a single rod or pipe requires a supplemental electrode (250.53(A)(2)), which may be another rod or pipe at least 6' away (250.53(B)).]

Cheers, Wayne

 

[ramsy]

Could I bang a 3/4" pipe 8' deep at the boat house? The inspector is wanting me to run the GEC all the way back to dry land.

See 250.53(1)
Below Permanent Moisture Level.

Maybe SS rod & cable, or fence-in solar array at ground level

 

[BarklieEstes]

Thanks guys.

 

[tortuga]

The inspector is wanting me to run the GEC all the way back to dry land.

What I have seen on dock or pier is a feeder with a 30 mA GFPE breaker, the GFPE is like a GFCI but less sensitive the 30 mA trip 682.15 (B), then GFCI on the outlets 150V to ground up to 60A 682.15(A), I don't think your expected drive ground rods in the water, just at the disconnect on land but check article 682 and 555 and see if they apply to your situation.