Grounding two separate systems

[Mrgulabull]

I have a bit of a strange setup and after lots of searching have been unable to find an answer on how to properly ground my systems.

I am completely off grid, and have two inverters that each have their own separate AC panels. One inverter is always on and powers the majority of the house loads. The second is only occasionally used to power the washer / dryer, and is otherwise switched off.

I have driven a ground rod and bonded neutral / ground on the main inverters AC panel that I use for the majority of my loads. However, I have not grounded the second inverters AC panel as I’m concerned that this setup may create a ground loop, or some other safety issue.

Everything I’ve read has said to only bond neutral / ground in one location. I’m not sure how that applies when I have two separate systems that both need grounding.

Any advice or suggestions are greatly appreciated, thanks for your time!

 

[sunshine_eggo]

Both systems should have an N-G bond and be earthed.

Please see link #4 in my signature from linked time to 14:37 (about a minute)

If:
Panel 1:
N-G bond at panel and earthed.

Then:
Inverter 1: N-G bond should be broken. Most off-grid inverters have an N-G bond if inverting.

Panel 2:
N-G bond at panel OR inverter
Panel 2 G to Panel 1 G

Thus:
System 1 has one N-G bond.
System 2 has one N-G bond.
They are both connected at G and earthed.

 

[Mrgulabull]

Sorry, I don’t quite follow. Are you saying to break the N / G bond on the first inverters panel and only have it on the second AC panel? Or are you saying to N / G bond on both AC panels?

Just to confirm, the systems are completely separate on the AC side and as far as I’m aware there is no N / G bond on the inverters.

Thanks for your time and advice!

 

[sunshine_eggo]

Sorry, I don’t quite follow. Are you saying to break the N / G bond on the first inverters panel? Or are you saying to N / G bond on both AC panels?

I am saying that most off-grid inverter/chargers have an internal N-G bond unless it is deliberately broken by the installer. If you have a low-end inverter-only, this may not be the case.

Just to confirm, the systems are completely separate on the AC side and as far as I’m aware there is not N / G bond on the inverters.

Understood, but "as far as I'm aware" should be "I'm certain".

1 N-G bond per system (at the AC panel or inverter)

Tie the two panels to each other via a single G-G connection.

That way both systems have a single N-G bond with only one path to Earth.

 

[Mrgulabull]

Thank you.

I just checked and confirmed the second inverter is floating, there is no continuity between N and G on the AC output (48v growatt 3000 TL LVM’s). I’m seeing ~55v on the second inverters neutral line, where as the first inverter (which is grounded to earth) shows 0v between N and G.

In this case, would it make sense to bond N / G on the second inverters AC panel (which is confirmed to be floating), or is there another place I should connect G for the second inverter to avoid a ground loop?

 

[sunshine_eggo]

Thank you.

I just checked and confirmed the second inverter is floating, there is no continuity between N and G on the AC output (48v growatt 3000 TL LVM’s). I’m seeing ~55v on the second inverters neutral line, where as the first inverter (which is grounded to earth) shows 0v between N and G.

Sounds good.

In this case, would it make sense to bond N / G on the second inverters AC panel (which is confirmed to be floating),

Yep.

or is there another place I should connect G for the second inverter to avoid a ground loop?

As long as you don't do it in two places, you're good. Once bonded at the panel, you should have 120V between L and G at the inverter.