Confused on grounding of a string inverter when line-tapping for net-metering.

[busydad]

All,

I'm stuck on a grounding issue for my string inverter ground mount. I've built a 12kw ground mount array that is using a Fronius Symo 3-phase inverter that is 208-240. This is going to be a grid-tie system that will run directly to the meter with a line-tap. We are bypassing the distribution panel (my breaker panel) because its on the opposite side of the the house from my meter. My electric meter is mounted on a pole with a disconnect and then the feeder cable runs under ground into my house and to the distribution panel.

I know I need to ground the panels to 1 or 2 grounding stakes at the array itself. Where the confusion sets in is that I've also been told that I need to run another ground from the array to the distribution panel (breaker panel) that's in my house and tie into the existing ground. Then I'm told I don't have to do this cause I'm tying in at the meter not at the panel.

Can anyone shine some light on this dilema for me.

Thanks
Bob

 

[zanydroid]

Who is telling you this? They are very confused, or the advice is being combined inappropriately. Some of it sounds objectively wrong.

Does "Distribution Panel" mean main panel (IE where the N-G bond is formed)?

Is the wire from meter to distribution panel L-L-L-N-G or L-L-L-N?

Shouldn't there be an electrician or engineer involved with designing for a 120/208 facility?

The EGC going to the array is non-negotiable and always has to be bonded with the grounding system for the structure, IE it needs a properly sized fault path back to the N-G bond of the system.

The ground rod at the array is optional, and most of the grounding experts on this forum are against it.

 

[garetwo]

I know I need to ground the panels to 1 or 2 grounding stakes at the array itself.

Is this for lighting?

 

[BentleyJ]

You only need one earth ground, but more is allowed, so in theory you could run a ground wire from the array in the same bundle with the line-side tap conductors IF the ground rod is near the service entrance/disconnect. I suspect ground may actually be located near your main breaker panel along with the N-G bond. The choice here would be to add a 2nd ground rod near the disconnect just for the solar array and associated metal equipment or possibly relocate the main ground to the area of the disconnect and pull a new ground wire over to the breaker panel. (ya, the one you didn't want to mess with, LOL) In the latter case, I'm not 100% sure but then the N-G bond should be moved to the disconnect?

Hopefully, timselectric or pvgirl can help here since they have a firm grasp of the NEC.

 

[timselectric]

One question. How is the disconnect on the pole grounded?
The array EGC should be connected to the same thing.

 

[busydad]

One question. How is the disconnect on the pole grounded?
The array EGC should be connected to the same thing.

The disconnect on the pole has a lug where the neutral comes in from the meter. That is where the ground wire is attached that then runs down the pole and into the "ground".

 

[zanydroid]

That sounds promising, if I understand the setup you should be able to backfeed the inverter here.

Is there a neutral-ground bond at the next subpanel down from this (I believe you said this is at your house)? There should not be one, but there should be a ground rod at that structure that is connected to the ground bar in that subpanel.

Is there a desire to future proof / simplify installing a hybrid system? If so line side tap is not the way to go, though probably you could just reconfigure this later for not much extra cost. Really depends on how much trenching is involved (if any) for the inverter to disconnect wiring. If there is trenching then you may want to pull extra wire to support hybrid setup in the future since it's cheaper to do now.

Did you confirm with POCO that line side tap is allowed in your area?

 

[timselectric]

The disconnect on the pole has a lug where the neutral comes in from the meter. That is where the ground wire is attached that then runs down the pole and into the "ground".

That is where you need to connect the array EGC.

 

[timselectric]

To clarify.
The array EGC should be run along side of the array circuit conductors. To the inverter. And then from the inverter (along with the circuit conductors) to the tap point. And connected to the existing grounding system at the pole.