Grounding Wire Connection for Fronius GT Inverter question

I am reviewing my manual and I came across this wiring scheme which I need help clearing up:

Attachment not found.

My interpretation is:

L1 - is to L1 of the incoming grid. So I take it to the main panel.

L2 - is to L2 of the incoming grid. So I take it to the main panel.

N - is to N of incoming grid. So I take it to the main panel.

GET - is to the rod stuck in the earth, the grounded electrode.

G-PV - is to the frames of the solar panels themselves.

Here is my doubt:

Grid Grounding - this is a crossover to the N cable mentioned above which goes to the grid Neutral?

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,629 admin
    Re: Grounding Wire Connection for Fronius GT Inverter question

    No, the Neutral should be "isolated" in the GT inverter--It is just another power lead (on the inverter side). That is, by the way, the explanation for north American 120/240 VAC split phase power.

    For 230 VAC systems, you have an L1 and N connection only (if they even earth bond neutral in some countries). In your case of 230 VAC (or other) power, L1 is simply Hot and N is simply the AC return wire. Actual polarity should not matter unless the inverter is measuring the Neutral to Chassis ground voltage (I don't know if this is required, or if this is even done).

    Regarding ground rod, panel frame, and green wire ground connections...

    Boy they are making it complex.

    In North America... I would be telling people that live in lightning prone areas to ground the panel frames directly to the ground rod (down the outsize wall of the the building to a ground rod driven close to the wall/foundation). And running at 6 AWG from the remote ground rod (if not the same as the building's main AC Ground rod) to the main AC ground rod and call it a day.

    Connect the green wire from AC main panel to the earth ground screw in the panel chassis (or if you use metal conduit, the conduit itself may supply the ground).

    Here--It looks like they are bringing the Panel Frame Grounds into the GT box and dropping an another cable to a local ground rod. Not great for lightning.

    And the two terminals (2 and 3) are marked the same--And imply that these grounds are connected to the chassis of the of the GT inverter.

    Multiple earth to ground connections in an AC power system is certainly not standard--But I am not sure that it is against code. And I am not sure it is a "bad thing". However, bringing Panel Frame Ground inside the home, I think that is not a good thing (if lightning strike).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • quiquequique Solar Expert Posts: 252 ✭✭
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Yeah I don't like that pv frame ground at the inverter. I was thinking of grounding it directly to the ground electrode in the earth. But I'm confused about that last grid ground terminal. I don't think my main AC panel has a ground wire. It has never been a custom here in Honduras.
  • BB.BB. Super Moderators, Administrators Posts: 30,629 admin
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Ideally, all "metal" in the electrical and plumbing systems are tied together with a ground wire. That way, any short circuit in the home will trip the upstream fuse/breaker and prevent an electrical box or sink/stove/etc. from becoming "Hot".

    And the "Neutral" is bonded to the same plumbing/piping ground to provide a return current path for the short circuit to the main panel and eventually out to the utility transformer.

    It is always "interesting" when somebody wires in a electrical device from one country into another country's power grid. You have to ask questions about ground/utility power configuration to make sure that nothing "goes wrong".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • quiquequique Solar Expert Posts: 252 ✭✭
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Ok so:

    1: GET is connected to the grounded electrode in the ground

    2: Is connected to the ground wires from my pv panels

    3: Is connected to the ... ground wire from the main AC panel? Which if I don't have one, I would have to lay it from the main AC panel to the grounded electrode in the backyard...
  • BB.BB. Super Moderators, Administrators Posts: 30,629 admin
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Or do #1 and #2 outside the building (array frames to ground rod/bonding to metal cold water pipe type and or ground rod).

    And #3 to your AC system Ground wire (or conduit to the rest of your AC power system if you use conduit in your home).

    However, from the documentation, I have no clue if #3 is connected to inverter chassis or simply connected to #1 and #2. Normally #3 is a green screw driving into the main sheet metal/chassis of the GT inverter.

    Figure out what #1, #2, #3 are connected to.

    Figure out what you what you want need to have happen if there is a "Hot" to GT chassis short circuit. There should be some return current path to your main AC panel so the GT inverter sheet metal does not become "hot" and shock you. That is the basic function of the green wire (or conduit) ground connection/neutral bonding.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • quiquequique Solar Expert Posts: 252 ✭✭
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Ok Ill take a closer look at the manual.

    One other thing...when connecting L1 (GT) to L1 (MainsPanel) and likewise for L2s...is it important which is L1 & L2 in the MainsPanel, which I don't know.

    Iow, does L1 represent a significantly different line from L2 such that if we connect L1 to L2, it would be a problem?
  • quiquequique Solar Expert Posts: 252 ✭✭
    Re: Grounding Wire Connection for Fronius GT Inverter question

    Here is the answer I got from Fronius support:

    Hi

    I have a question about wiring my ig plus v 3.0uni.

    I'm in Honduras where we have a single split phase 120/240.

    I'm wondering about the ground connections.

    I understand the GET terminal (1) is for wiring out to my ground electrod rods in the ground.

    I understand pv grounding terminal (2) is for the incoming wire from my pv array frame ground wire.

    But I need to clear up Grid grounding terminal (3). (A) Is this for the ground wire from my mains AC panel? Because my mains AC panel doesn't have a ground wire. I would have to install it.
    Yes in the US it is necessary that you ground the AC side too. So the grounding terminal (3) is to do this. If you have no AC ground it is not necessary to install them because you have a ground electrode rod.

    (B) what about the grounding of the GT Inverter chassis?
    The grounding of the inverter chassis is done directly in the housing and it is connected to the grounding terminal.

    Thanks

    ---

    So do I just wire my pv array ground down to my rod in the earth and that's it?

    I checked and even though my AC mains panel doesn't have a ground bar with ground wires in it, the neutral is bonded to a ground at the utility meter. Of course that doesn't do me much good in my AC panel. So should I also run a green grounding wire from my mains panel to the rod in the earth and then from that mains ground rod to the inverter as well?
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