Please check my 7 KW off-grid diagram

[jsocolof]

The inverters seems to have N-G connection in inverter mode. Only one of them should have that connection.

The inverters are coordinating their operation in split-phase mode. Each inverter is supplying a separate buss in the AC distribution panel. I believe both N-G relays should be enabled to handle needed grounding events for the separate branches. Does this make sense?

 

[jsocolof]

As long as the generator is un-bonded then the inverters can be un-bonded and the only bond should be at the main panel.
The primary reason that inverter/chargers have a bonding relay is so that they can be temporarily connected to a pedestal where the bond will be upsteam and out of one's control when you are attached but within the inverter when you not connected.

The way I see it there are two ways I could do this:
1. Enable the N-G bonding relay in the inverters which will handle the N-G bond in inverter mode. Don't bond N-G at the AC panel. Use an N-G bonded generator, which will open the relays at the inverters and the only N-G bond will be at the genset.

2. Bond N-G at the AC distribution panel, disable the relays in the inverters, and use a floating neutral genset.

Currently taking votes...

Are both are equally safe? Neither is particularly hard to execute...

 

[CamoGreg]

Wouldn’t you get a grounding loop when both inverters have the N-G bond?

I believe as long as the two Victron inverters are linked with comms and setup in a split phase or parallel configuration, they are assigned a master/slave relationship where the master unit controls the N-G bond relay.

 

[jsocolof]

I believe as long as the two Victron inverters are linked with comms and setup in a split phase or parallel configuration, they are assigned a master/slave relationship where the master unit controls the N-G bond relay.

I believe this is correct, too. I will have comms between them.

 

[John Frum]

Wouldn’t you get a grounding loop when both inverters have the N-G bond?

I know what you mean and I agree but the term "ground loop" has a lot of baggage that obscure your meaning.

 

[jsocolof]

I've proposed a passive solution with 0 moving parts.

That's a strong argument for my #2 solution above...

2. Bond N-G at the AC distribution panel, disable the relays in the inverters, and use a floating neutral genset.

 

[jsocolof]

I am now installing the equipment I've been discussing in this thread. Grounding in solar setups is not simple or clear. I've opted to let the Quattros employ their N-G bonds in battery/inverter mode, and have an N-G bond at the generator for genset mode. In wiring the Quattros' AC out to the AC distribution panel, I have a ground wire from the Quattros. What do I do with it? In my AC distribution panel, there is a neutral buss as usual. In a house fed from a grid, I would connect the ground to the neutral buss, but I don't want an N-G bond in the panel. Do I use the ground wires from the Quattros only as a case ground at the AC panel? When I wire AC circuits into the panel, do I still connect both the neutral and ground wires from the circuits to the neutral buss?

 

[Ellis Redding]

I am now installing the equipment I've been discussing in this thread. Grounding in solar setups is not simple or clear. I've opted to let the Quattros employ their N-G bonds in battery/inverter mode, and have an N-G bond at the generator for genset mode. In wiring the Quattros' AC out to the AC distribution panel, I have a ground wire from the Quattros. What do I do with it? In my AC distribution panel, there is a neutral buss as usual. In a house fed from a grid, I would connect the ground to the neutral buss, but I don't want an N-G bond in the panel. Do I use the ground wires from the Quattros only as a case ground at the AC panel? When I wire AC circuits into the panel, do I still connect both the neutral and ground wires from the circuits to the neutral buss?

Been a long time since I looked at your setup, but the big question is always grid tied vs off-grid. Grid tied being the most complicated (in my opinion). You should definitely do some investigation around that.

 

[OffGridInTheCity]

I am now installing the equipment I've been discussing in this thread. Grounding in solar setups is not simple or clear. I've opted to let the Quattros employ their N-G bonds in battery/inverter mode, and have an N-G bond at the generator for genset mode. In wiring the Quattros' AC out to the AC distribution panel, I have a ground wire from the Quattros. What do I do with it? In my AC distribution panel, there is a neutral buss as usual. In a house fed from a grid, I would connect the ground to the neutral buss, but I don't want an N-G bond in the panel. Do I use the ground wires from the Quattros only as a case ground at the AC panel? When I wire AC circuits into the panel, do I still connect both the neutral and ground wires from the circuits to the neutral buss?

The ground/neutral is connected together at the main panel of a home ONLY. At sub-panels you keep the neutral and grounds separated. There are several youtubes discussing this - here's one that may help illuminate the issue a bit more

 

[jsocolof]

There are several youtubes discussing this - here's one that may help illuminate the issue a bit more

Thank you - this was very helpful. When I realized that the main AC panel in an off grid solar setup is a sub-panel, it all clicked. The grounding conductors that come from my inverters to the AC panel are equipment grounding conductors and should be attached to the grounding buss on the panel case, which will not be bonded to the neutral. The ground wires coming in from the AC circuits will be attached to the grounding buss, and the neutral wires to the neutral buss. Correct?

 

[OffGridInTheCity]

Thank you - this was very helpful. When I realized that the main AC panel in an off grid solar setup is a sub-panel, it all clicked. The grounding conductors that come from my inverters to the AC panel are equipment grounding conductors and should be attached to the grounding buss on the panel case, which will not be bonded to the neutral. The ground wires coming in from the AC circuits will be attached to the grounding buss, and the neutral wires to the neutral buss. Correct?

Yes, you got it and that's exactly what I did. But I'm not an electrician, so I cannot advise. Maybe someone else will add comments.