Off-Grid Ground & Victron Lynx

[victronoffgrid]

Hi There,

I'm building out a 800w 12v off grid solar setup for a small cabin with Victron components (Muliplus ii, Lynx, Cerbo & 406amh Epoch 12v). I have 4/0 running from batteries to invertor and invertor to Lynx. Only 2/0 fits on the chassis ground of the MPii to the lynx. I had planned on using 4/0 to ground to a ground plate outside of the cottage but it doesn't look like they accept that high of gauge. So that has me rather stumped....

The 3000/12/120 manual shows a 12AWG for the ground, but I'm going to assume that's just a chassis ground.

I'll have DC running to a distribution panel and AC to on Out1 to a 50amp panel (with no ground).

Any idea's on how I can ground the system via the lynx? Everything I've read says the wire should match power source. Any help would be much appreciated.

 

[timselectric]

You are trying to follow the mobile system guidelines. But this is a stationery system.
Do not ground the battery negative (or positive for that matter).
You ground the AC system just like any other house.
The grounding system begins at and is created by the N/G bond.
If the Multiplus doesn't create the N/G bond for you, you must do it yourself. (Usually this will be done in the main service panel)
Then everything else is bonded (grounded) back to this point.
Including, but not limited to........
Equipment enclosures, solar panel frames and racking (if conductive), the earth, water service, gas service, metal junction boxes and conduit.

 

[victronoffgrid]

Thanks - that’s incredibly helpful. Would that also mean that the case ground on the inverter and mppt should also be removed from their connections back at the lynx?

 

[timselectric]

Thanks - that’s incredibly helpful. Would that also mean that the case ground on the inverter and mppt should also be removed from their connections back at the lynx?

Yes
They should also be connected to the grounding system.

 

[SoakedUp]

You are trying to follow the mobile system guidelines. But this is a stationery system.
Do not ground the battery negative (or positive for that matter).
You ground the AC system just like any other house.
The grounding system begins at and is created by the N/G bond.
If the Multiplus doesn't create the N/G bond for you, you must do it yourself. (Usually this will be done in the main service panel)
Then everything else is bonded (grounded) back to this point.
Including, but not limited to........
Equipment enclosures, solar panel frames and racking (if conductive), the earth, water service, gas service, metal junction boxes and conduit.

Say we have the Multiplus creating our N/G bond and is feeding a main service panel from the AC out. Do all EGCs from equipment enclosures, solar panel frames, etc. run back to the Multiplus or can they be terminated in that service panels grounding busbar?

 

[timselectric]

Say we have the Multiplus creating our N/G bond and is feeding a main service panel from the AC out. Do all EGCs from equipment enclosures, solar panel frames, etc. run back to the Multiplus or can they be terminated in that service panels grounding busbar?

Either is fine, but the service panel is the simpler option. As it's already designed to accommodate more connections.

 

[Cmiller]

Say we have the Multiplus creating our N/G bond and is feeding a main service panel from the AC out. Do all EGCs from equipment enclosures, solar panel frames, etc. run back to the Multiplus or can they be terminated in that service panels grounding busbar?

Solid advise from @timselectric here! I second everything he said! I would also add that personally I prefer disabling the internal bond relay option on the Multiplus and just making the bond in the breaker panel myself! I know the inverter is designed to have that option, but I feel that in a stationary, permanent install, it is much better to just plain have a solid ground jumper in your main panel that you don't ever have to worry about. And then if the inverter ever fails and you yank it off the wall and hook in a generator temporarily, your bond is still in place! Where the bonding relay works well is for mobile applications, where the unit is regularly getting plugged into a large electrical power source (grid).

 

[victronoffgrid]

Would anyone have a diagram to share showing the desired or similar setup?

Based on the information above where the Multi is handling the N/G we should ideally run a nice green sleeved cable (copper ground wire) from MPPT & Multi back to panel and then ground stake from there. What about the Lynx? In all the mobile designs they are run back to the ground screw on the Lynx and then down from there. My newb brain seems to think that's a DC ground connection and doesn't link back to the AC run. Makes sense in mobile because the frame is DC.

I've excluded the panels from the above as I was told there is little benefit to grounding 800W in series unless I'm trying to prevent from a lightening strike. Given everything noted above, I'm going to assume that was incorrect and the panel cases should be connected back to electrical box.

Would you wire one size down on each application (i.e 4/0 get 2/0, 2AWG from MPPT gets 4AWG, 8AWG from panels gets 10AWG)?

6AWG from the panel to ground (current code in Ontario).?

 

[timselectric]

Based on the information above where the Multi is handling the N/G we should ideally run a nice green sleeved cable (copper ground wire) from MPPT & Multi back to panel and then ground stake from there.

Correct

What about the Lynx?

No

I've excluded the panels from the above as I was told there is little benefit to grounding 800W in series unless I'm trying to prevent from a lightening strike. Given everything noted above, I'm going to assume that was incorrect and the panel cases should be connected back to electrical box.

Correct

Would you wire one size down on each application (i.e 4/0 get 2/0, 2AWG from MPPT gets 4AWG, 8AWG from panels gets 10AWG)?

Grounding conductor is sized according to the OCP (Over Current Protection) of the circuit it's ran with.

6AWG from the panel to ground (current code in Ontario).?

#6 to the grounding electrode (ground rod/ spike) is correct.

 

[timselectric]

 

[victronoffgrid]

timseletric - much appreciated. I'm finally comfortable with the required items. Cheers