250.52(a) (2)

[wyboy]

250.52(A) (2)
How can building steel be connected to a concrete encased electrode (rebar). The code just says connect. Is rebar tied to J bolts ?connected?? Also if a water pipe comes up at one end of the building and the service is at the other, and the service is large enough to require a 3/0 WP grounding electrode conductor, can you still carry the electrode back on the rebar? Would you have to use a 3/0 UFER in that case?

 

[raider1]

250.52(A) (2)
How can building steel be connected to a concrete encased electrode (rebar). The code just says connect. Is rebar tied to J bolts ?connected??

Yes, if the J-bolts of a concrete pier are tied with tie wire to the CEE then the building steel is effectively grounded. The 2011 NEC section 250.52(A)(2) was modified to reflect this.

Also if a water pipe comes up at one end of the building and the service is at the other, and the service is large enough to require a 3/0 WP grounding electrode conductor, can you still carry the electrode back on the rebar? Would you have to use a 3/0 UFER in that case?

You can use the re-bar of the CEE to interconnect other electrodes provided that the GEC connected to the CEE is sized based on Table 250.66. So in you example if you needed to have a 3/0 for the water pipe you would need a 3/0 run to the re-bar in the footing and a 3/0 bonding jumper run from the re-bar back up to the water pipe.

Chris

 

[eprice]

250.52(A) (2)
Also if a water pipe comes up at one end of the building and the service is at the other, and the service is large enough to require a 3/0 WP grounding electrode conductor, can you still carry the electrode back on the rebar?

You can also use the building steel to do this. As long as the grounding electrodes (building steel, water pipe, and CEE) are bonded together as required by 250.50, 250.64(F)(1) allows the GEC to be connected to any convenient electrode. If the water pipe is on the other end of the building, the building steel may be the most convenient.

 

[don_resqcapt19]

...
You can use the re-bar of the CEE to interconnect other electrodes provided that the GEC connected to the CEE is sized based on Table 250.66. So in you example if you needed to have a 3/0 for the water pipe you would need a 3/0 run to the re-bar in the footing and a 3/0 bonding jumper run from the re-bar back up to the water pipe.

Chris

Chris,
What code section permits the use of the rebar and the bonding jumper between parts of the grounding electrode system? In the 2011 code 250.68(C)(2) makes it clear that you can use the steel structure of the building for this purpose, and the exception to (C)(1) permits the use of the metal water pipe, with restrictions, but I don't see anything that says we can use the re-bar.

 

[raider1]

Chris,
What code section permits the use of the rebar and the bonding jumper between parts of the grounding electrode system? In the 2011 code 250.68(C)(2) makes it clear that you can use the steel structure of the building for this purpose, and the exception to (C)(1) permits the use of the metal water pipe, with restrictions, but I don't see anything that says we can use the re-bar.

If I make my bonding jumper connection directly to the re-bar in the footing and don't use a section of re-bar that is run outside of the concrete to interconnect the water pipe then I am connecting directly to an electrode and 250.68(C) would not be needed as we are not extending an electrode connection.

I do see that there may be a question if you stick the re-bar from the footing up out of the concrete for the connection.

Chris

 

[gndrod]

Ufer

Ufer

[250.68(C)] does relax the interior water pipe within 5' foundation exit requirement with exception for commercial, industrial and institutional structures, but not in residential configurations. So there are two different answers for compliance in that regard. For the CEE connection according to [250.66(B)] as permitted in 250.52(A)(3), the sole connection of the GEC to the grounding electrode (CEE) shall not be required to be larger than 4 AWG Cu.

Using a J-bolt or bolts to secure a proper UFER bonding may be pretty tricky depending on what kind of steel structure ties into the concrete foundation in commercial and definitely in residential. If the top perimeter #4 or larger rebar is used to bond the j-bolts, there is almost a guarantee that the vertical rebar risers will be #3 to tie into the lower structure footing #4 rebar. According to the NEC, not being #4 in itself is a code violation. [250.52(3)(1)] "not less than 13mm(1/2 in.")

In addition, the concrete will have the exterior foundation mastic sealed below grade level from direct contact with the earth. The upper perimeter rebar that bonds to the J-bolts can be disqualified from being part of the grounding electrode system. The NEC has progressively painted themselves into the proverbial UFER ground corner by not giving attention to other interfacing trades code requirements since the NFPA and TCC have tried to create a better mouse-trap beginning from the 2005 code cycle. No fault of theirs, they just didn't have any concrete guys sitting on the CMP's.

My only answer to the OP is to check with the approved project specs and the local AHJ rules.

 

[renosteinke]

Rebar is no different from any other 'made' electrode. There is no requirement that grounding electrodes be UL listed; only that they meet certain criteria. The UL listing only becomes required in the special case of when you want to use a slightly undersized steel ground rod as your electrode.

If you were making a grounding grid with wire, you would have to use special connections. With rebar in concrete, the usual simple tie wires used are perfectly adequate. It's not the rebar that's the electrode - it's the entire slab. Rebar is just a good connection point.

 

[gndrod]

If you were making a grounding grid with wire, you would have to use special connections. With rebar in concrete, the usual simple tie wires used are perfectly adequate. It's not the rebar that's the electrode - it's the entire slab. Rebar is just a good connection point.

I agree about the wire ties as long as the rebar is #4 or larger. Generally a slab on grade will not pass as a foundation compliant UFER for an electrode grounding system due to the plastic membrane requirement over the crushed rock base. The integral turned slab footer will have the rebar directly in the poured footer on natural hardpan. The rebar must be encased 3" for structural compliance in the footer. (IRC R403.1.3.1) The NEC 2" in concrete works as long as the rebar is not part of the seismic foundation.