Grounding electrode

[Gnole]

I have a home with a existing 200 amp service that is grounded to earth with two rods. Now the owner has constructed a detatched mother-inlaw cottage to be feed from building 1 with a 100 amp circuit.Our local AHJ requires us to use the steel in the footer but the buildings cocrete is already poured and the buildings up, (cottage only) Is required in 2005 Nec? Why couldnt we just use two additional rods?
Thanks, Gnole

 

[George Stolz]

Our local AHJ requires us to use the steel in the footer but the buildings cocrete is already poured and the buildings up, (cottage only) Is required in 2005 Nec?

Yes, if it is present, it is required to be used - 250.32(A) leads you to 250.50. All electrodes present at each structure must be used.

Why couldnt we just use two additional rods?

Because that would not relieve you of the code requirement to use all the electrodes present. You can pave the yard with ground rods, and still have to use the metallic water pipe, the concrete encased electrode, building steel, etc, if it is present. Adding more of a different electrode doesn't negate the requirement to use the ones available.

You might be able to strike a deal with the AHJ, but you will not find relief in the NEC. You might be chiseling concrete.

 

[infinity]

The steel rebar in the footing is only required to be used if it's 1/2" or larger. The CEE connection should have been inspected when the footing inspection took place. If the rebar is smaller than 1/2" a CEE is not required. You'll need to work this out with the inspector, as George said you may need to get out the chopping gun.

 

[chris kennedy]

The steel rebar in the footing is only required to be used if it's 1/2" or larger. If the rebar is smaller than 1/2" a CEE is not required.

Then 20' of #4 bare or larger is required.

If you want to PO the inspector, point him to what is IMO the poorly worded exception to 250.50.

You do in fact have an existing building.

 

[iwire]

Then 20' of #4 bare or larger is required.

NO!

You are never required by the NEC to install a uffer.

If the steel is large enough and present then you are required to use it.

If the steel is not there or not large enough then you can forget about the uffer or you can voluntarily install 20' or more off 4 AWG.

 

[chris kennedy]

Our local AHJ requires us to use the steel in the footer

I agree Bob.

 

[romeo]

Grounding electrode

NO!

You are never required by the NEC to install a uffer.

If the steel is large enough and present then you are required to use it.

If the steel is not there or not large enough then you can forget about the uffer or you can voluntarily install 20' or more off 4 AWG.

Thats what I always thought and that is how I treat it while inspecting.

 

[Pierre C Belarge]

If you want to PO the inspector, point him to what is IMO the poorly worded exception to 250.50.

You do in fact have an existing building.

There would have to be a CO on that building for it to be considered existing...I doubt there is a CO on that building as it is under construction.

 

[infinity]

Then 20' of #4 bare or larger is required.

As Bob said this is incorrect. You are not required to make a CEE if one doesn't exist. 20' of 1/2" or larger rebar must be used, smaller rebar or no rebar, then no CEE required at all.

 

[petersonra]

I have a home with a existing 200 amp service that is grounded to earth with two rods. Now the owner has constructed a detatched mother-inlaw cottage to be feed from building 1 with a 100 amp circuit.Our local AHJ requires us to use the steel in the footer but the buildings cocrete is already poured and the buildings up, (cottage only) Is required in 2005 Nec? Why couldnt we just use two additional rods?
Thanks, Gnole

Look closely at what the code actually requires. You may not actually need to connect to the steel for one or more reasons.

One reason another poster has already mentioned. Perhaps rebar was used that is not 1/2" or better. Perhaps no rebar at all. Some places allow mesh instead of rebar.

It may also be that the footing is not in direct contact with the soil. Sometimes they spray waterproofing around the footing itself and set the footing on a gravel base, so there is no direct connection between the soil and the footing. If that were the case, you would not need to connect to the steel. Sometimes gravel is laid around the footing so it is not exposed directly to the soil. No soil, no connection to steel required, IMO.

Some buildings do not even have traditional footings or foundations.

 

[chris kennedy]

As Bob said this is incorrect. You are not required to make a CEE if one doesn't exist. 20' of 1/2" or larger rebar must be used, smaller rebar or no rebar, then no CEE required at all.

I'm not seeing this. 250.50 says if present shall be bonded together...

250.52(A)(3) says or 20' of bare copper...

So I walk up to the footer and the rebar is smaller than 1/2", but to my good fortune 20' of #4 bare was "present" in the footer.

Bob, Trevor point me in the right direction as to why a UFER is not required if present.

Thanks

 

[Pierre C Belarge]

Trevor
The 1/2" rebar is treated like the steel or water, it is present when the building is being built. The 20' of copper would have to be added (made) such as ground rods or a ground ring. It is not present while the building is being built.

Another way you may look at this is such:
the footing/foundation, steel and water are typically installed by other trades, hence they are "present". The copper conductor is generally installed by the electrician, hence it is "made".

 

[iwire]

So I walk up to the footer and the rebar is smaller than 1/2", but to my good fortune 20' of #4 bare was "present" in the footer.

I guess if someone added the 20' of 4 AWG before you got there it is present and must be used.

However, has this ever happened?

Has the copper fairy left 20' of 4 AWG bare in a the footing just waiting for an EC to come along?

 

[Pierre C Belarge]

I guess if someone added the 20' of 4 AWG before you got there it is present and must be used.

However, has this ever happened?

Has the copper fairy left 20' of 4 AWG bare in a the footing just waiting for an EC to come along?

When I was a kid, the "tooth fairy" would come and leave quarter under our pillow and take the tooth we had lost. I always thought that was so cool.

Now we have a "copper fairy"...I think it is time to come back into the contracting trade, what with the price of copper and all.

 

[chris kennedy]

Has the copper fairy left 20' of 4 AWG bare in a the footing just waiting for an EC to come along?

Bob we all know that the copper fairy makes copper disappear.

I didn't think about it this morning when you said the NEC never requires a UFER. Then I got thinking never is a pretty strong statement. Where do you get that from?

 

[iwire]

I didn't think about it this morning when you said the NEC never requires a UFER. Then I got thinking never is a pretty strong statement.

That is not what I said.

What I said was this....

You are never required by the NEC to install a uffer.

And I stand by that statement. :smile:

 

[Pierre C Belarge]

That is not what I said.

What I said was this....




And I stand by that statement. :smile:

The last sentence in 250.50 (not including the exception) lends credence to your statement.

 

[chris kennedy]

That is not what I said.

What I said was this....




And I stand by that statement. :smile:

Great, why? As I read 250.50, if its present you use it. Help me out here.

 

[iwire]

Great, why? As I read 250.50, if its present you use it. Help me out here.

Yes, if it is present.

Why would the copper be there if you did not choose to install it?

I think we are just having a communication breakdown.

 

[M. D.]

I found this and I agree though the words changed the requirement remains the same . The concrete is a structure and it exists do not chip away at it. I think this is still accurate

http://www.mikeholt.com/mojonewsarchive/NECQ-HTML/HTML/NEC_Questions008~20030808.htm
[FONT=Arial, Helvetica, sans-serif]Q9. I remember reading somewhere that an inspector couldn't make a contractor chip out the footer to create a concrete encased electrode. Is there such a ruling and if so could you quote it. It seems to me that chipping out the footer creates a building code violation.

A9. No the NEC does not require that a concrete encased electrode be made accessible. If the concrete is already poured, then it's simply not available. I base my comments on the NFPA Formal Interpretation 78-4, which is contained in the NEC Handbook.
Reference: Article 250.50
Question: Is it the intent of 250.50 that reinforcing steel, if used in a building footing, must be made available for grounding?
Answer: No.
Issue Edition: 1978
Reference: 250-81
Issue Date: March 1980[/FONT]