Addition Ufer Grounding

[KFB]

I am working on an attached house addition; I am adding a 100 amp 120/240 vac sub main to the addition from the existing 200 amp main located approximately 100? away. The building contractor has stubbed up a piece of rebar for me to ground to. I was going to tie a piece of #6 copper from the rebar to the new sub-panel?s ground bus, but after re-reading Art 250, am I required to install an un-spliced #4 copper all the way to the 200 amp main panel from the rebar? Since the original panel has its ground rod and CW ground, am I even required to ground the additions rebar? Could you please enlighten me on interpreting art 250?

Thanks
KFB

 

[infinity]

The subpanel does not require a GE connection. IMO the new CEE does not need to be connected if the old service is not being touched. The existing service is just that, existing, and code compliant as is.

If you do want to connect the new CEE to the existing service you may connect it to the existing GEC going to the water pipe, if this distance shorter. You don't need to go all the way back to the service.

 

[KFB]

Ufer ground

Ufer ground

I understand that the new sub panel does not require the Ufer ground, but are you required to ground the new attached addition? This is the 2nd time (two different jurisdictions) that I have been told I have to provide a Ufer ground on an addition, but I cannot find it in the code. Anyway since the Ufer ground was located directly below the new panel (5? away) I was going to consider it an auxiliary ground and was going to attach it to the new sub, but after re-reading 250 I don?t think I can.

 

[hillbilly]

I understand that the new sub panel does not require the Ufer ground, but are you required to ground the new attached addition? This is the 2nd time (two different jurisdictions) that I have been told I have to provide a Ufer ground on an addition, but I cannot find it in the code. Anyway since the Ufer ground was located directly below the new panel (5? away) I was going to consider it an auxiliary ground and was going to attach it to the new sub, but after re-reading 250 I don?t think I can.

In my opinion....250.54 would allow you to connect the ufer to the new sub panel (feeder) grounding conductor.
You are running a 4 wire feeder to this new sub-panel...correct?

steve

 

[macmikeman]

Your existing service already has connections to a grounding electrode in order to "limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines?as per 250-4(A)(1)" . The existing service complied with code when it was installed, and you are not touching it. The code does not state that if new footings are added to a building then a new uffer ground needs to be installed into the existing service. I does however in so many words require that when installing a new service that all grounding electrodes present as per 250.52 be used.

 

[lpelectric]

I certainly don't see any harm in it IMO. Hook the CEE to the EGC in the new remote panelboard and let it "hitchhike" across the 4th wire (EGC) to the main disconnect 100 ' away at the 200 amp panel where it will become part of the grounding electrode system. :smile:

 

[George Stolz]

I agree with the others that the NEC would not have you do anything with this CEE in this circumstance, but that does not mean the AHJ will not insist on it. Check with them before proceeding, IMO.

Actually, come to think of it: This principle of "I'm not messing with the old service, so I can ignore new electrodes" concept really isn't in the NEC, is it? I'd say it's just a typical attitude of AHJs, as opposed to being linked to some specific language in the NEC, no?

Hook the CEE to the EGC in the new remote panelboard and let it "hitchhike" across the 4th wire (EGC) to the main disconnect 100 ' away at the 200 amp panel where it will become part of the grounding electrode system. :smile:

I don't see a problem with that in the functional sense, but if the AHJ insists on this being a required 250.50 electrode, then that plan of attack would violate 250.64(C).

 

[lpelectric]

I don't see a problem with that in the functional sense, but if the AHJ insists on this being a required 250.50 electrode, then that plan of attack would violate 250.64(C).

Very astute! :smile: This is one of the many reasons I enjoy this forum.

 

[tryinghard]

I understand that the new sub panel does not require the Ufer ground...Anyway since the Ufer ground was located directly below the new panel (5? away) I was going to consider it an auxiliary ground and was going to attach it to the new sub, but after re-reading 250 I don?t think I can.

You can install your GEC to ?any convenient grounding electrode available? 250-64(F) but I think you should be mindful of length. Install it to the closest electrode, if the GEC is long it runs the risk of failing by blowing in half when routing lightning and items as described in 250-4(A)(1).

 

[lpelectric]

I agree with the others that the NEC would not have you do anything with this CEE in this circumstance, but that does not mean the AHJ will not insist on it. Check with them before proceeding, IMO.

Actually, come to think of it: This principle of "I'm not messing with the old service, so I can ignore new electrodes" concept really isn't in the NEC, is it? I'd say it's just a typical attitude of AHJs, as opposed to being linked to some specific language in the NEC, no?


I don't see a problem with that in the functional sense, but if the AHJ insists on this being a required 250.50 electrode, then that plan of attack would violate 250.64(C).

George: I have a question about this. What if I called this CEE for the addition a "supplemental" grounding electrode? Would I then be able to use the provisions of 250.54 to allow me to "hitchhike" on the EGC? Just wondering...? :smile:

 

[George Stolz]

...if the GEC is long it runs the risk of failing by blowing in half when routing lightning and items as described in 250-4(A)(1).

Do you have any evidence of this ever occuring?

What if I called this CEE for the addition a "supplemental" grounding electrode? Would I then be able to use the provisions of 250.54 to allow me to "hitchhike" on the EGC?

LP, yes, I agree with that. Steve had mentioned doing that above.

I wouldn't call it "hitchhiking" per se, because that CEE connection isn't doing much good for anything, IMO. It could be argued that you're dragging whatever the CEE is supposed to be getting rid of (lightning, line surges, evil spirits) into the electrical system.

 

[lpelectric]

Do you have any evidence of this ever occuring?


LP, yes, I agree with that. Steve had mentioned doing that above.

I wouldn't call it "hitchhiking" per se, because that CEE connection isn't doing much good for anything, IMO. It could be argued that you're dragging whatever the CEE is supposed to be getting rid of (lightning, line surges, evil spirits) into the electrical system.

Thank You :smile:

 

[tryinghard]

Do you have any evidence of this ever occuring?

No I sure don’t but it follows the same rational as that of grounding for communication antenna television and radio distribution system Article 820 and 820-40(A)(4) Oops thats 2002 05 is 820-100(A)(4) “The grounding conductor shall be as short as practicable…not to exceed 20 ft in length.”

The functions for the grounds are identical.