Two buildings and grounding AC/DC

[diy-greg]

Hi! I have this setup: https://www.mermaidchart.com/raw/81...e908c7f8d?theme=light&version=v0.1&format=svg
Where I have building 1 with the solar array and 15 meters away building 2 with inverter etc.
Building 2 already has one grounding rod for AC, but this grounding cannot be used for DC grounding because mixing DC ground with AC is not recommended?

So I would need 2 separate grounding rods at building 2 (One for AC and one for DC), and not use grounding rod at building 1, because of potential interference when a lightning would strike between the buildings for instance. Is this correct?

It is a hybrid inverter, without grid tie, so the grid provides power to the inverter, and from the invterter I have the rest of the existing AC system.

 

[Q-Dog]

but this grounding cannot be used for DC grounding because mixing DC ground with AC is not recommended?

Never heard of this (but I'm not in Thigh-land). Do you have a link to this recommendation?

 

[diy-greg]

Unfortunately not. I was hoping I could do a TT "island" grounding at building 1 by connecting the solar frame to the rod at building 1. Then connect the rest of the ground DC and AC to the main rod at building 1. But that does not go well with my DIY solar guy. I might need to ask a different solar guy....

 

[robbob2112]

We have a couple of folks that answer from Thailand.... they do things with regard to grounding and neutral wires different fo those of us in the US.

Paging @Norwasian for input

If he doesn't show up soon search his name and grounding in the upper right of the page.... he can teach a lot.

 

[Norwasian]

We have a couple of folks that answer from Thailand.... they do things with regard to grounding and neutral wires different fo those of us in the US.

Paging @Norwasian for input

If he doesn't show up soon search his name and grounding in the upper right of the page.... he can teach a lot.

Well, some of that grounding practice may be dependent on where in Thailand one resides. Thailand is better than Laos, where I once lived, but is still unpredictable at times. I don't see any reason that an AC ground could not be mixed with a DC ground unless one is experiencing issues from the utility such as I had in Laos where the transformer center tap was used as one of the three-phase legs, and one of what should have been a phase took the place of the center tap as ground. Essentially the earth ground was "hot" in this scenario, and I would not wish to mix it with the ground of a DC circuit--though I'm still not sure how they would interact. Perhaps a certified electrician here can venture to think outside the norm and suggest what the ramifications of a miswired transformer would be to use of the earth ground.

For my part, to this day I do not dare to install an electric water heater in my home due to concerns over grounding irregularities here.

However, my main reason to avoid grounding altogether and opt for an isolated system is based on the potential for lightning surge, and not so much the actual circuit theory. Lightning has yet to trouble me since I isolated my inverter system. If one is grid-connected, grounding is probably best, but for off-grid situations, the benefits of grounding, at least where I am, are much less clear.

 

[diy-greg]

Thank you Norwasian.

The whole AC box in the house is grounded to the AC earth, and it AC neutral is also connected to the ground bus bar.

On the "Solar/DC" side my solar guy would like to connect SPD, Solar panel array frame and inverter frame to a ground bus bar which then is connected to a separate DC earth rod.

AC grid powers inverter and inverter powers the rest of the building.

 

[Q-Dog]

I think if both AC and DC equipment are in the same structure and can interact with each other, they should have a common ground. It might depend on the equipment. But, I admit I don't know as much about grounding as I should, especially when it comes to mixing AC and DC in the same structure.

@timselectric is the grounding guru around here, maybe he has some thoughts??

 

[diy-greg]

Also this is Thailand with local installation setup, so I might need to provide more info, but which info is needed?

Thanks!