Share grounding rod in PV/Mains hybrid?

[Richiep]

I'm designing a PV and battery system to be used in a building that already has Mains power. Would it be ok to share the same grounding rod? Or should I drive a separate rod for the PV system?

Thanks
Rich

[max2k]

I'm designing a PV and battery system to be used in a building that already has Mains power. Would it be ok to share the same grounding rod? Or should I drive a separate rod for the PV system?

Thanks
Rich

couple questions:
- why do you need batteries if you already have grid power? It is expensive hobby.
- are you using 'grounding' here in a sense of EGC or lightning protection?

take a look, especially around 7:50 mark on how lightning strike looks 'electrically': https://www.youtube.com/watch?v=YuDqXFvRv94

[Richiep]

take a look, especially around 7:50 mark on how lightning strike looks 'electrically': https://www.youtube.com/watch?v=YuDqXFvRv94

Wow! Mike Holt is an amazing resource!

Short answer, yes you can and should share a grounding rod.

Thanks!
Rich

[Gdwats]

Wow, again. I thought a system ground was required, so I drove 2 8' rods in the ground 6 feet apart connecting the first to the second with wire running from top of one to 18" down on the second. Attached grounds from system and hurried the whole thing up. Then I saw a single grounding rod for the house sticking up with a corroded, broken off ground clamp dangling there in pieces. Should I call the owner? Should I just re attach it? Should I attach it to my rod(s).

ps OP: not meaning to flood your post. Thought pertinent.

[max2k]

Wow, again. I thought a system ground was required, so I drove 2 8' rods in the ground 6 feet apart connecting the first to the second with wire running from top of one to 18" down on the second. Attached grounds from system and hurried the whole thing up. Then I saw a single grounding rod for the house sticking up with a corroded, broken off ground clamp dangling there in pieces. Should I call the owner? Should I just re attach it? Should I attach it to my rod(s).

ps OP: not meaning to flood your post. Thought pertinent.

if the owner is not someone close to you I'm surprised they're OK with any alterations you're doing especially on the electrical side. One thing is to call and complain about disconnected grounding wire and completely different is to connect your system to their grounding rod without their consent. Even home owners need to get that 'consent' from local AHJ as insurance / neighbors want to be sure they are not burning the whole block down as a result of their 'improvements'.

[Gdwats]

Not what I asked

[max2k]

Not what I asked

I doubt what you're doing is legal and as such any path you take will be as good as any other- you're on your own.

[Mike90250]

Grounding is a sticky wicket and I'm not ever giving any advice on it, because it is so important, and there are so many regions that have different requirements, But I can say go to your building office, explain what you have, what you discovered, and ask what THEY want you to do to meet their current rules.

I don't think bringing lightning into your home through a panel is a good idea, but some areas still have that in their code, and I can only throw my hands up in the air.

Watch the Mike Holt videos on Grounding and Lightning and you will start to get an idea of whats state of the art.

[neweclipse]

NEVER allow ANY of your body parts to get in between a 'dangling' service ground wire and earth and/or grounded electrode, it can KILL!!!
It is an 'open circuit' and may have potiential voltage that will cause you to 'hung up' and unable to leave go once in contact with it.

Call an Expert!!!

[Gdwats]

Thank you all. My stuff is all isolated and safe. Nothing is tied to the house. Just a fused a.c. inverter inside. Will watch video. I'll ignore what I discovered. Will be moving again soon.

[Gdwats]

Watched video. Left me confused, and didn't apply to a non house instal really. Left me thinking my 2 bonded rod ground was dangerous.

[max2k]

Watched video. Left me confused, and didn't apply to a non house instal really. Left me thinking my 2 bonded rod ground was dangerous.

depends how that bond is made - if it bonds 2 rods together with dedicated wire and then the rest of your equipment connected to that at 1 point it's OK but if both of them are connected to your system with individual wires it is not. Lightning is very fast event (in uS range) with very high current reaching hundreds of kA. Those hundreds of kA going to the ground through 'resistors' in Ohms range create hundreds of kV voltages. Due to short times inductance of those wires matter too- you can have DC connection which presents high impedance at those short times meaning that path will be simply 'ignored' by lightning charge and it will find some shorter alternative nearby.

[Mike90250]

Here's the graphic showing bringing in Lightning to your house

If you have a heavy ground wire in a trench, connecting the 2 electrodes, that provides a easier path, and the lightning goes around your house (mostly)

GroundingElectrode_MHolt.png

[Gdwats]

Yes, one 8' rod bonded to the other 6 feet away with awg4 grounding wire from top of one rod to 18" from top of other. All equipment is then grounded to just the one rod, and all is now covered up.

[Gdwats]

Here's the graphic showing bringing in Lightning to your house

If you have a heavy ground wire in a trench, connecting the 2 electrodes, that provides a easier path, and the lightning goes around your house (mostly)

GroundingElectrode_MHolt.png

I see, that is what i have, but nothing I've done is grounded or connected in any way, to the house. Yes, the bonding ground wire is awg4, a but overkill.