Grounding Rod Location

[bmxdad]

Can a grounding rod, if needed, be installed inside a building?

My idea is to install it before the concrete is poured, under the sub-panel. Since there might need to be two at 6' apart?, the other would also be installed as the first, but farther down the wall. The grounding wire connecting them would be fed through 1" schedule 40 conduit, and then up into the sub-panel.

Thoughts ...

 

[gasaxeman]

Better put ground rod outside.
When installed inside they dry out and loose conductivity with the earth.
That has been my experience with some old services we have run across.
We have had to redo grounds and have put the electrodes on the exterior of the building.
A ufer ground which is attached to the rebar grid is a different animal.

 

[softailgarage]

Just installed one in the garage floor for the plumbing. Different ground I suppose.

 

[rockwithjason]

Can a grounding rod, if needed, be installed inside a building?

My idea is to install it before the concrete is poured, under the sub-panel. Since there might need to be two need at 6' apart?, the other would also be installed as the first, but farher down the wall. The grounding wire connecting them would be fed through 1" schedule 40 conduit, and then up into the sub-panel.

Thoughts ...

the connection from the grounding electrode conductor to the rods must be accessable. you will have to install some kind of door or handhole to accomodate this. no need for conduit, just run the wire thru the studs and avoid any contact with other metals. all 8ft of the rod must be below ground, not sure how you are going to pull that off. any fittings you use to connect the grounding electrode conductor must be rated for direct burial.

 

[alfredeneuman]

s. all 8ft of the rod must be below ground, not sure how you are going to pull that off.

The easy fix to this is to just use a 10' ground rod. You'll comply with the 8' in soil rule.

 

[rockwithjason]

i just read the 2011 code and it seems you are right. I thought i had heard some talk of the rod being completely buried regardless of length but it's probably a local amendment or an inspector's preference.

 

[justsam]

Will you be using rebar in the concrete that is yet to be poured?

If you are using rebar, why not use a Ufer ground. If no rebar than #4 or greater copper, a minimum of 20 feet in the concrete.

Need to check with local jurisdictions if they accept Ufer ground.

 

[sberry]

I like to get them to a drip edge. In my own am connected to a whole building uffer and have a huge footing right to ground water. Got a couple rods too, it didn't cost much and was done a long time ago.
The one real problem I had was the phone co didn't ground their service and it cost me some greif. I went back to art 880 I believe and ran a wire one upsize from code to system ground and now it blows their suppression like it should only once.
Ideally is pointed rods or electrodes in to the water table, that's about as good as it gets.

 

[bmxdad]

Will you be using rebar in the concrete that is yet to be poured?

Nope, no rebar

... If no rebar than #4 or greater copper, a minimum of 20 feet in the concrete.

Need to check with local jurisdictions if they accept Ufer ground.

So I could get a 20'+ piece of #4 copper wire and stretch it across the pad area towards the opposite wall, so its in the concrete when poured and that's a Ufer?

 

[sberry]

Putting it in the bottom of a footer would be better.

 

[bmxdad]

No footer ... this is a pole garage with a floating? slab.

 

[justsam]

Nope, no rebar



So I could get a 20'+ piece of #4 copper wire and stretch it across the pad area towards the opposite wall, so its in the concrete when poured and that's a Ufer?

Yes. It just needs to be a minimum of 20 feet. It does not need to be in a straight line necessarily.

Check with your local jurisdiction about their requirements but I am sure they would accept it.

 

[alfredeneuman]

Ufer ground are required to be in the footing.

No footing, no Ufer ground.

 

[Aceman]

the connection from the grounding electrode conductor to the rods must be accessable. you will have to install some kind of door or handhole to accomodate this. no need for conduit, just run the wire thru the studs and avoid any contact with other metals. all 8ft of the rod must be below ground, not sure how you are going to pull that off. any fittings you use to connect the grounding electrode conductor must be rated for direct burial.

Connections to concrete-encased, driven, or buried electrodes don't need to be accessible. 250.68(A)Exception 1.

I've driven many rods under slabs before they've been poured. As long as the inspector looks at it first, it's not an issue.

 

[bmxdad]

Reading 250.52(3) Grounding Electrodes ...

 

[James-W]

I don't understand why you feel it is important to have the grounding rods inside rather than outside. I don't see how the reason could be cosmetic because the grounding rods for our garage are outside next to the building. They are covered u with dirt and there is grass planted over the top of them. You don't even know the grounding rods are there. There is a conduit coming into the building near the breaker panel in a very inconspicuous place that contains the grounding wire.

I guess my question is, if the reason for having the grounding rods under the slab isn't cosmetic, then what is the reason for doing it? But with a little prior planning you can put the grounding rods outside in a location where nobody (except you and the inspector) will ever know they are there.

 

[bmxdad]

There is none ... if I can keep everything in the same location ... good, if not ... Oh-Well. I guess I could have some conduit exiting the building ... thats actually a good idea. Thanks.

 

[bullnerd]

My local utility company has all the info on their website, including diagrams of whats acceptable.