Fronius IG Plus V 3.0uni ground wiring

Hi guys, I just want to run this by you because the grounding wires are confusing me.

First, a drawing of my setup:

Attachment not found.

The thing is, I don't have a ground bar at my Main AC Panel. We recently moved the utility meter due to regulations and we noticed the neutral from the grid is grounded at the meter. But the Main Panel doesn't even have a ground bus bar.

LEFT TO RIGHT--->
A. We connected the PV Array ground wires to a solid cable that goes straight into the ground rod electrodes at the back of the property.

B. We connected DC Disconnect ground bus bar straight to that ground rod electrode.

C. We connected DC Disconnect ground bus bar into the inverter terminal #2, the PV grounding terminal according to the manual.

D. We connected DC Disconnect to the AC Disconnect ground bus bar.

And I was thinking of taking 1 more wire from the AC Disconnect ground bus bar to the Mains Panel.

Now my wiring inside the inverter:

Attachment not found.

1. Ive got the DC+ coming in from the DC disconnect...
2. Ive got the DC- coming in from the DC disconnect...
3. The L1, L2 & N coming in from the AC disconnect (which is connected to the mains panel on a double 30a breaker & neutral bus bar respectively)
4. Finally the only ground wire in Terminal#2 is coming in from the DC Disconnect box ground bus bar where all other grounds connect.

What's wrong or missing from this setup?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    The first thing I see wrong is this:
    the Main Panel doesn't even have a ground bus bar.

    How, in this day and age, is that even possible? Are their not bare wires coming in with every load circuit? What do they attach to?

    What we'd expect to see: service transformer's neutral line grounded at the pole. This will be irrelevant if the house is taken off grid. Main service panel has neutral and ground bus bars. They are tied together in some way with the one and only allowed neutral-ground bond. Ground bus bar is also attached to Earth grounding in some way.

    If what you describe is truly the case the problem is with the actual AC distribution wiring and not with the inverter. It sounds as though it utterly lacks a ground. In that case running one from (apparently missing) ground bus bar at the AC distribution panel to the Earth grounding rod should be done.

    The inverter expect the wires from the PV, including the frame/mount grounding wire, to travel through the DC disconnect and to the inverter. Then the ground from that point would go to Earth ground. This is where you get into code trouble because most of us do not want to run the PV ground into the house as it increases the risk of introducing lightning to the house. You've done the right thing to wire around it in my opinion, as both grounds are connected to the same point only the PV line has been left entirely outside the structure.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    Ok I already bought the bus bar to put into the mains AC panel and I actually already threaded the ground wire from the AC disconnect to the mains panel. I would just need to wire that mains grnd bus bar to the earth rod.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring
    quique wrote: »
    Ok I already bought the bus bar to put into the mains AC panel and I actually already threaded the ground wire from the AC disconnect to the mains panel. I would just need to wire that mains grnd bus bar to the earth rod.

    Possibly not. If you have a wire going from the mains ground bus bar to the ground bus bar in the AC disconnect and then a wire from that bar to any other point connected to the Earth ground rod you do not want to run another wire from the mains ground bus bar to the Earth ground rod. This will create a ground loop if you do.

    I may have to draw a picture here.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    Ok I was basing the idea on this model I saw in a training book.

    Attachment not found.

    Where a connection is made at the inverter and at the mains panel.

    My current setup has this:

    Attachment not found.

    Where the dotted green lines are planned.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    The top image in the photo actually shows two Earth ground points tied together to act as one. They may have left out the details about that line between the two ground points.

    Your sketch shows two Earth grounding points not tied together, and that creates the ground loop problem. The connecting between the two grounding points is Earth, which makes the resistance between them variable and unpredictable. That potentially turns the grounding wires, rods, and Earth into a circuit wherein something shorted at one point in the wire may energize other points in respect to ground because of the unreliability of the ground contact. Yes, it's complicated.

    You can connect the ground from each or any individual component directly to one ground rod.
    You can connect the ground from a component to another component and so forth and end up at the one ground rod.
    You can ground some things at one rod and others at another if the distance between the rods is large (and the inspector doesn't object; they often do).
    You can't connect the ground from one component to another and have a ground rod "at each end" of that wire.
    But you can if the two ground rods are tied together underground with more wire.


    So either connect the ground bus in the AC main panel with its own wire to the ground rod or;
    Connect the ground bus in the AC main panel to the other components ground wire that goes to that rod or;
    Connect the ground bus in the AC main panel to its own ground rod but not to the other component grounding wire or;
    Connect the ground bus in the AC main panel to the other component ground wires and to its own ground rod but tie that rod to the other rod.

    Of these the third choice is the one most likely to raise eyebrows and not be allowed.

    How much distance would there be from the ground rod to the AC main panel?
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    Well I thought your 2nd option is what I was attempting:

    Connecting the mains AC panel ground bus bar to the other components ground (at the AC disconnect ground bus bar).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring
    quique wrote: »
    Well I thought your 2nd option is what I was attempting:

    Connecting the mains AC panel ground bus bar to the other components ground (at the AC disconnect ground bus bar).

    Yes, but your sketch also shows a line from the AC mains panel to a second Earth ground. That should not be there.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Fronius IG Plus V 3.0uni ground wiring

    Oh ok so this is what you are proposing:

    Attachment not found.

    1. The wire running straight from the solar panels to the 3 grounding rods I have in the earth. (Grounding Conductor).
    2. DC bus bar --- grounding conductor.
    3. DC bus bar --- AC bus bar.
    4. DC bus bar --- Inverter

    5. AC bus bar --- Mains bus bar or chasis