Ufer ground

[Frank Samhammer]

I have a single family home with an 8foot basement foundation wall. The contractor is using a #2 stranded copper Ufer for a 400 amp service embedded 8 feet in the footing leaving 12 feet to run through foundation wall to the service panel. My question is in the footing can you tie off the #2 with tie wire to the steel or do you have to use rated ground clamp.

Thanks,
Frank Samhammer

 

[stickboy1375]

250.70........................

 

[Dennis Alwon]

I have a single family home with an 8foot basement foundation wall. The contractor is using a #2 stranded copper Ufer for a 400 amp service embedded 8 feet in the footing leaving 12 feet to run through foundation wall to the service panel. My question is in the footing can you tie off the #2 with tie wire to the steel or do you have to use rated ground clamp.

Thanks,
Frank Samhammer

I would use rated ground clamps. Also #2 is more than you need-- 4 copper is adequate art. 250.52(A) (3). The reinforcing rods shall be permitted to be bonded together with tie wires.

My technic is to use 20' of #4 bare copper and clamp it to the rebar. Many people have the concrete guys bend a piece of the rebar into the crawl space by the panel.

 

[infinity]

The GEC is required to be terminated with a listed fitting. As Dennis said the GEC to the CEE only needs to be a #4 cu conductor for any size service.

 

[tryinghard]

In your case go with listed clamps in 250-70. But if the #4< cu is installed as per 250-52(A)(3) it can just simply be tied, because the #4 installed 20' on the bottom of the foundation is the electrode.

Be careful to have the full 20' on the bottom and additional for the riser through the footing.

 

[JohnJ0906]

Be careful to have the full 20' on the bottom and additional for the riser through the footing.

Welcome to the forum Frank. :smile:

It sounds as if they are only leaving 8' of wire in the footer. There needs to be 20', as tryinghard said.

 

[Dennis Alwon]

Welcome to the forum Frank. :smile:

It sounds as if they are only leaving 8' of wire in the footer. There needs to be 20', as tryinghard said.

There are 2 things going on here. One is you can have 20' #4 copper just laying in the footer as a cee or/and if your rebar is 1/2" minimum than you must use the rebar. If you bond to the rebar you do not need 20' in the footer. In fact, if the rebar is tied together in the footer and the rebar is bent out of the footer than you don't need any copper in the footer. All you need is whatever length it takes to clamp to the rebar.

 

[tryinghard]

There are 2 things going on here. One is you can have 20' #4 copper just laying in the footer as a cee or/and if your rebar is 1/2" minimum than you must use the rebar...

Dennis,

I do not see where one must use the rebar?

In 250-52(A)(3) does say or bare copper. Your right as far as stubbing the bar up but there's nothing to stop from using the copper as the electrode with rebar and not stub the rebar.

Often we use bare copper and we install 20' on the bottom bar with tie wire and a clamp at the end (just because). This copper is the electrode and can simply stub out of the footing. The electrode conductor can clamp to this to route to the service disconnect.

 

[gndrod]

less cost

less cost

Dennis,

I do not see where one must use the rebar?

In 250-52(A)(3) does say or bare copper. Your right as far as stubbing the bar up but there's nothing to stop from using the copper as the electrode with rebar and not stub the rebar.

Often we use bare copper and we install 20' on the bottom bar with tie wire and a clamp at the end (just because). This copper is the electrode and can simply stub out of the footing. The electrode conductor can clamp to this to route to the service disconnect.

Hi tryinghard,

Most Ufer installs I have done in CA, NV, WA...were using the #4 rebar footers that the GC agreed to install with a stub up from the stemwall in the location of the main panel. Usually the #4 copper length amounted to 8' at the most. In all cases, the AHJ required accessible inspection of the GEC clamped with a Junior weaver direct burial clamp to the rebar. Reason, different inspectors doing follow-on inspections want to see the Ufer bonds. Most initial inspection cards do not list buyoff on rebar bonds. It's just one of those minor details that don't happen until the next inspector comes along.

This is probably the most economical, code compliant electrode bonding that I can think of other than switching over to acorns (1980's) that are about one buck cheaper. Using #4 Cu x 20' costs about 12 more feet in copper. The above installs were done from 1971 till recently. Incidently, rebar in the garage slab monolithic footer is also a compliant install.

The above methods probably have different requirements across the US so the above might need pre-approved consent by the AHJ. rbj

 

[infinity]

Dennis,

I do not see where one must use the rebar?

The OP says that he's using only 8' of conductor within the footing, therefore he must use the rebar since he doesn't have the minimum of 20' of bare copper.

 

[tryinghard]

The OP says that he's using only 8' of conductor within the footing, therefore he must use the rebar since he doesn't have the minimum of 20' of bare copper.

Thanks Trevor, I did notice this at the beginning but I thought Dennis was referencing 250-52(A)(3) as must rather than this specific application.

Hi tryinghard, Most Ufer installs I have done in CA, NV, WA...were using the #4 rebar footers that the GC agreed to install with a stub up from the stemwall in the location of the main panel. Usually the #4 copper length amounted to 8' at the most. In all cases, the AHJ required accessible inspection of the GEC clamped with a Junior weaver direct burial clamp to the rebar...rbj

This is most common here as well but (residentially) we did have a contractor that wanted the electrician responsible for the electrode regardless so we installed the 25' of #4 to the service disconnect location at the same time we installed the service underground stub-outs. There was always underground to do for this contractor anyway.

If the 20' of #4 is installed as the electrode it does not have to run continuous to the landing lug (although it can) but the GEC does have to run continuous from the electrode stub to the landing lug.

Thanks for your input

 

[petersonra]

I don't see where he has the choice to use the footer rebar or not. if it is there, he has to use it regardless of whether he puts in 20' of #4 in the concrete.

 

[A/A Fuel GTX]

I don't see where he has the choice to use the footer rebar or not. if it is there, he has to use it regardless of whether he puts in 20' of #4 in the concrete.

I agree.....If the electrode is present, it must be used. If there were no rebar in the footing, then the 20' of #4 would be an option.

 

[Dennis Alwon]

I don't see where he has the choice to use the footer rebar or not. if it is there, he has to use it regardless of whether he puts in 20' of #4 in the concrete.

Thank you. I do agree that all grounding electrodes that are present must be used. Here is the 2008 art., however 2005 is the same at least in reference to what is discussed here.

III. Grounding Electrode System and Grounding Electrode Conductor
250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.
Exception: Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete.

In the OP situation the 8 ' in the footer won't get it. Now if his rebare is less than 1/2" then he may opt for the 20' in the footer or drive 2 ground rods.

It would seem that the 20' in the footer would be a must, if the rebar wasn't present or less than 1/2", but I don't see it that way.

 

[tryinghard]

I agree with you guy?s regarding the OP. But a point I?m trying to make is 250-52(A)(3) ufer can be "either or" even though ?? rebar exists.

Notice 250-52(A)(3) says electrode located within/near bottom of foundation, consisting of at least ??x20? rebar

-----OR-----​

#4 cu x 20?

-----BUT-----​

Rebar shall be permitted to be bonded with ties

-----SO-----​

Rebar is not an electrode until it is ?? & 20? at bottom & stubbed up.

#4 is not an electrode until it is #4cu & 20? at bottom & stubbed up.

If ?? x 20? rebar does exist but does not stub up (no contractor deal) then #4cu & 20? at bottom & stubbed up can, and it IS the electrode in this fashion, even if one chooses to connect it to the rebar in footing at the end.

 

[Dennis Alwon]

Read 250.50 as stated above. It is required for all that exist.

All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system

.

Where does it say it must be stubbed up. It is our responsibility to get them to stub it up.

 

[iwire]

I agree with tryinghard and in the 2008 it is made clearer.

Look at the last sentence of 250.52(A)(3) 2008.

I think the change had more to do with commercial buildings that had multiple electrically separate footings but it also applies to the discussion at hand.

 

[Dennis Alwon]

I agree with tryinghard and in the 2008 it is made clearer. Thank Bob

Look at the last sentence of 250.52(A)(3) 2008.

I think the change had more to do with commercial buildings that had multiple electrically separate footings but it also applies to the discussion at hand.

I see that the 2008 has made it clear and I will have to agree--- it is either one or the other. Here is the art.

250.52(A)3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (? in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. Where multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

 

[Dennis Alwon]

I still think 250.52(A)(3) is contradicting 250.50. There looks like there should be a change in 250.50 that says except in case of multiple concrete encased electrodes with a reference to 250.52(A)(3).

Sounds like a change would be appropriate.

 

[infinity]

It sounds quite clear to me. If the 20' or more of 1/2" or larger rebar is present you must use a CEE. The CEE can be either the rebar or 20' of bare #4 cu.