Off grid cabin ground plan

[ezwryder]

I've been reading all the discussions about grounding and bonding and trying to apply that to my off grid cabin set up. If you don't mind I'd like to ask if this diagram looks about right. My system is pretty simple, I do not have any grid ties or generators. I know a lot of people ask so I'd just appreciate your comments if you happen to see any big red flag items. Comments about system particulars are below the diagram and I thank you in advance for your thoughts.



Starting from the left, inside cabin…

Solar component ground connections are wired to a common ground bus bar
Ground bus bar is connected to ground at main service panel
Line, neutral, ground leads from inverter to main service panel
Main service panel neutral is bonded to ground with supplied bonding screw
Two 8 foot ground rods spaced 6 feet apart with EGC to main panel
Note: Victron states the inverter’s AC output neutral is not bonded to ground.

Inside the shed…

Line, neutral, ground run to sub panel in shed about 40 feet (total wire length) from main panel
Sub panel is not neutral-ground bonded
A separate pair of 8 grounding rods are installed and connected to sub panel
Solar panel frames are grounded and run to ground on sub panel

One question I have is about the need for multiple ground rod installations. I watched the video that someone else posted about grounding and it sounded like the presenter was recommending just one grounding point. I see the logic in that. However I'm pretty sure local code requires ground rods for the main service panel and the sub panel in the shed.

 

[12VoltInstalls]

Well first thing is you:
1) maybe don’t need a dirt/earth/AC ground rod to begin with
2) if you have a ground rod or proximal paired ground rods for a 120VAC/240VAC system (from the bonding panel as depicted) YOU NEVER HAVE TWO PATHS TO GROUND just the one from the panel that contains the bare/green/ground and white/neutral bond.

separate pair of 8 grounding rods are installed and connected to sub panel
Solar panel frames are grounded and run to ground on sub panel

If that pair of shed rods is for the solar panels to be grounded then they should not be mixed inside an enclosure with any 120VAC/240VAC which is how I’m reading that diagram.

You are off grid so there is no path/circuit to the grid ‘source of power’ unless one makes a path.

There are some jurisdictions that do require a dirt/ground/earth for offgrid, there are other jurisdictions that do not have that policy. NEC defines circumstances where a ground rod is needed for off grid.

The master electricians or practicing EE’s that participate on this site can clarify my statements and provide the guidance needed re: NEC and offgrid.

 

[sunshine_eggo]

Note: Victron states the inverter’s AC output neutral is not bonded to ground.

This is an option.

Default behavior: Internal relay supplies the N-G bond when inverting. When on AC input, internal relay opens breaking the N-G bond.

"Ground Relay" is an option in VEConfigure3. If that option is UNselected, the inverter will never supply the N-G bond.

 

[ezwryder]

This is an option.

Default behavior: Internal relay supplies the N-G bond when inverting. When on AC input, internal relay opens breaking the N-G bond.

"Ground Relay" is an option in VEConfigure3. If that option is UNselected, the inverter will never supply the N-G bond.

That is a good observation, thank you for bring that to my attention. So if I allow the inverter to perform the N-G bond then I do not want a bond at the service panel, would that be correct?

 

[ezwryder]

Well first thing is you:
1) maybe don’t need a dirt/earth/AC ground rod to begin with
2) if you have a ground rod or proximal paired ground rods for a 120VAC/240VAC system (from the bonding panel as depicted) YOU NEVER HAVE TWO PATHS TO GROUND just the one from the panel that contains the bare/green/ground and white/neutral bond.

If that pair of shed rods is for the solar panels to be grounded then they should not be mixed inside an enclosure with any 120VAC/240VAC which is how I’m reading that diagram.

You are off grid so there is no path/circuit to the grid ‘source of power’ unless one makes a path.

There are some jurisdictions that do require a dirt/ground/earth for offgrid, there are other jurisdictions that do not have that policy. NEC defines circumstances where a ground rod is needed for off grid.

The master electricians or practicing EE’s that participate on this site can clarify my statements and provide the guidance needed re: NEC and offgrid.

Thank you for this feedback. I wasn't sure about achieving ground for the solar panels by connecting to the sub-panel in the shed. I will amend the plan to just run the solar panels to those grounding rods and I will look more at the NEC grounding requirements for the sub-panel.

 

[sunshine_eggo]

That is a good observation, thank you for bring that to my attention. So if I allow the inverter to perform the N-G bond then I do not want a bond at the service panel, would that be correct?

Or you could disable the relay in the inverter and retain the N-G bond at the panel.

 

[ezwryder]

Or you could disable the relay in the inverter and retain the N-G bond at the panel.

Yes, I think that is what I would prefer.