Earth grounding question

[Sparky7]

Hello,

I have a 4400 W magnum inverter charger with a mini panel. This is my main panel so it is grounded to the earth. The main panel is located in my attached garage. I have a sub panel for the house AC and another sub panel/remote panel in an outbuilding that is about 50 feet from the garage. The outbuilding panel is earth grounded and my solar array which is about 50 feet from the outbuilding also has an earth ground.

Everything has lightning protection including the pportable generator attached to the Inverter charger.

If I’m understanding Will’s video correctly the way I have the earth grounds set up it could cause damage to my equipment if there was a lightning strike?

Thank you

 

[sunshine_eggo]

Are your 3 earth rods bonded to each other?

 

[LakeHouse]

Hello,

I have a 4400 W magnum inverter charger with a mini panel. This is my main panel so it is grounded to the earth. The main panel is located in my attached garage. I have a sub panel for the house AC and another sub panel/remote panel in an outbuilding that is about 50 feet from the garage. The outbuilding panel is earth grounded and my solar array which is about 50 feet from the outbuilding also has an earth ground.

Everything has lightning protection including the pportable generator attached to the Inverter charger.

If I’m understanding Will’s video correctly the way I have the earth grounds set up it could cause damage to my equipment if there was a lightning strike?

Thank you

As above, "Are the Earth rods bonded to each other?", is the correct question to ask... But if you're new to this it might not be clear what that question means or why it might be important. What he's asking is: Is there a way for current to flow from any one of your earth grounds to any other earth ground. If there is, that's potentially a problem, and that's what Will's talking about damaging your system during a lightning strike: huge currents flowing from one of your earth rods to another, through your system.
Avoiding this seems easy enough, just isolate each earth ground system, and make sure you bond earth and neutral of your AC system (or earth and negative of your DC system if you're doing so) at exactly one location in the system. But it can be a little more complicated than that.
There's a great set of articles available in the resources section here: https://diysolarforum.com/resources/grounding-made-simpler-part-1-ac-houshold-grounding.157/

 

[sunshine_eggo]

A really good quick summary of the concept by Mike Holt is in link #6 in my signature.

 

[Sparky7]

I will have to check. I don’t remember specifically if I connected those grounds or not. I believe the remote panel in the shed to the main panel in the garage are connected. I don’t think the solar panel combiner box is though.

Thank you sunshine and lake house

 

[Sparky7]

Are your 3 earth rods bonded to each other?

Thay we're bonded. The bus bar in my combiner box was earth grounded to a copper ground rod right by the solar panels, and it also had a ground running to the main panel in the attached garage. I cut the ground wire in the combiner box that was running to the attached garage. 150 feet of 6 gauge solid cooper wire?

The main feed from my main panel to the remote panel in the outbuilding were also bonded to each other. I detached the ground wire inside The remote panel.

 

[timselectric]

Thay we're bonded. The bus bar in my combiner box was earth grounded to a copper ground rod right by the solar panels, and it also had a ground running to the main panel in the attached garage. I cut the ground wire in the combiner box that was running to the attached garage. 150 feet of 6 gauge solid cooper wire?

The main feed from my main panel to the remote panel in the outbuilding were also bonded to each other. I detached the ground wire inside The remote panel.

Backwards.
Code requires those grounding conductors.
You need to disconnect from the auxiliary ground rods. In order to avoid gradient pulse from a lightning strike.

 

[Sparky7]

Backwards.
Code requires those grounding conductors.
You need to disconnect from the auxiliary ground rods. In order to avoid gradient pulse from a lightning strike.

The codes are confusing. I thought the remote panel in the unattached building had to have its own ground rod.

So everything should be bonded to the one ground rod by the main panel?

 

[timselectric]

So everything should be bonded to the one ground rod by the main panel?

Yes, one grounding system.
Some jurisdictions want the auxiliary rod at detached buildings. If your inspector wants it. I would connect it for the inspection. And remove it after.

 

[Sparky7]

As above, "Are the Earth rods bonded to each other?", is the correct question to ask... But if you're new to this it might not be clear what that question means or why it might be important. What he's asking is: Is there a way for current to flow from any one of your earth grounds to any other earth ground. If there is, that's potentially a problem, and that's what Will's talking about damaging your system during a lightning strike: huge currents flowing from one of your earth rods to another, through your system.
Avoiding this seems easy enough, just isolate each earth ground system, and make sure you bond earth and neutral of your AC system (or earth and negative of your DC system if you're doing so) at exactly one location in the system. But it can be a little more complicated than that.
There's a great set of articles available in the resources section here: https://diysolarforum.com/resources/grounding-made-simpler-part-1-ac-houshold-grounding.157/

thank you for sharing these documents. I am reading them and trying to understand them.

 

[Sparky7]

From what I'm understanding is there should only be one earth ground source in the system.

In the AC document that Lakehouse shared there is a diagram that is a bit confusing. Why are there to ground rods? I thought the best practice was one?

 

[timselectric]

From what I'm understanding is there should only be one earth ground source in the system.

In the AC document that Lakehouse shared there is a diagram that is a bit confusing. Why are there to ground rods? I thought the best practice was one?

Most jurisdictions now require two ground rods at 6ft apart, for new service installations. This is just for a better connection. But it's still one connection (one unbroken conductor connects to both).
If your service is existing, this does not apply to you.

 

[Sparky7]

Most jurisdictions now require two ground rods at 6ft apart, for new service installations. This is just for a better connection. But it's still one connection (one unbroken conductor connects to both).
If your service is existing, this does not apply to you.

Thank you for clarifying that. I just put my system in two years ago and I did use two ground rods, but I wasn’t sure if this is what they were depicting. That makes sense now.

 

[oldmaninsaline]

The codes are confusing. I thought the remote panel in the unattached building had to have its own ground rod.

So everything should be bonded to the one ground rod by the main panel?

The way the NEC requirements read and are supposed to be enforced, bonding/grounding occurs at the main panel only and nowhere else. Keep in mind grounding and bonding are not the same. You'll want to look at Article 250 of the NEC and Section 250.4. It can get confusing very quickly. For instance, my generator is grounded and acts as the main panel because of the breakers in it, thus the panel in the cabin becomes a sub-panel and cannot be bonded but it can be grounded. When I mix in the solar and battery bank with the inverter it all changes around. Of course it depends on how conversant the inspector is with off grid applications.

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