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#96311 12/06/05 01:30 PM
Joined: Jul 2004
Posts: 9,923
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G
Member
One of the compromises I have seen tossed around is that they pour the "green" cell solid after the TUG inspection.


Greg Fretwell
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#96312 12/06/05 04:09 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Quote
Some struct. engineers are hyper-concerned about the moisture intrusuin problem. They will not let the the copper UFER be tied to the structural rebar.

I was not aware the was a choice available.

Quote
250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system.

If the rebar is there we must tie into it.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#96313 12/06/05 07:06 PM
Joined: Feb 2005
Posts: 44
B
Member
The first time I ran into the uffer ground was in sunny Las Vegas in the mid 1980's and we were required then to put the copper wire in the footer and tie it to the rebar and it was inspected and signed off by the same inspector that preformed the footing inspection. As I recall the building inspector did that. I'm not sure but I seem to remember them saying that they had to go and take a class so they would be qualified to inspect the grounding.
If we missed getting the uffer in or some low life cut it off, we had to dig a 2'x2'x2' hole, drive 4 stakes and coil 20 feet of cooper, and tie it to the stakes and pour it full of concrete. When this happened then we called the electrical inspector to inspected. All in all we didn't have that much problem with wire damage or thievery as we would sleeve it with PVC. When we got ready to tie it in to the service we just cut the PVC at the slab of bottom plate and put a little bit of pour stone in to seal up the PVC.
Since moving back east in the early 90's I have yet to see anyone use a uffer ground. The fact is I was suprised by how few of the electrical contractors here had ever heard of it.

#96314 12/06/05 08:26 PM
Joined: Sep 2004
Posts: 167
S
Member
We had a choice until about 4 months ago, when we went on the 2002 NEC.

I've yet to run into these types of engineers since se've been on the 2002.


Larry LeVoir
Inspector
City of Irvine, CA
#96315 12/06/05 08:50 PM
Joined: Mar 2005
Posts: 399
A
Member
Iwire,
I also thought the rebar must be connected. After the umpteenth time of reading about the concrete encased electrode IF 20 feet of #4 bare is used in the footer it becomes the concrete encased electrode and connection to the rebar is NOT required.
As an inspector I need to know all about this when we start making it mandatory.
Alan--


Alan--
If it was easy, anyone could do it.
#96316 12/07/05 08:16 AM
Joined: Nov 2000
Posts: 2,148
R
Member
Alan,
Quote
After the umpteenth time of reading about the concrete encased electrode IF 20 feet of #4 bare is used in the footer it becomes the concrete encased electrode and connection to the rebar is NOT required.
The installation of the copper does not make the rebar go away. The code section requires the rebar to be used as a grounding electrode if it is there. If both are there they both must be used.
Don


Don(resqcapt19)
#96317 12/07/05 12:13 PM
Joined: Mar 2005
Posts: 399
A
Member
I'm still tending to the idea that a concrete encased electrode is either the rebar or the 20 foot of #4.
If the rebar is there then A concrete encased electrode exist and must be used however the Code description of a concrete encased electrode from the beginning (250.52(A)(3) to the second comma first gives the location, from there to the next comma describes the rebar, then the word OR is used and the copper wire is described.
Unlike a swimming pool where the goal is to bond all the parts this is grounding so I believe that either the rebar OR the #4 wire achieves that goal.
Connecting the rebar to 20 feet of #4 wire will not substantially reduce the resistance to ground of the encased electrode.
[Ufer achieved >5 ohms in the desert. The difference between 5 & 2 1/2 ohms is negligable.]
250.50 requires all the listed electrodes to be bonded but, if the wire is the encased electrode and the rod is sealed in the cement then I would see no reason to bond the wire to the rerod.
I doubt if the reduction in resistance would be of as much benefit as not causing a problem for the structural integrity of the foundation.
Does anybody agree ?
Alan--


Alan--
If it was easy, anyone could do it.
#96318 12/07/05 12:46 PM
Joined: Jul 2002
Posts: 680
W
Member
Does this apply to slabs on grade??(contact with the earth?) and do you still have to drive 2 ground rods??

#96319 12/07/05 01:16 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
I can't speak for folks north of the 25th parallel but here in Florida a "slab on grade" will still have a footer poured as part of the slab. They ring the slab with a 12" x 8" "bell" footer. This has 2 #5 rebar in it. That gets tied to the dowel rods in the block cores you see in the top picture.
They put VisQueen under the slab portion but not under the footer portion.

As for the pool, you MUST attach to the pool steel. If you don't have steel or the steel is epoxy encapsulated 2005 code requires you to duplicate the steel with a 12x12 copper mesh. I think the same principle applies to footer steel.


Greg Fretwell
#96320 12/07/05 08:21 PM
Joined: Dec 2003
Posts: 751
E
Member
"680.26(C) The equipotential common bonding grid shall extend under paved walking surfaces for 1 m (3 ft) horizontally beyond the inside walls of the pool..." This sounds to me like only under the paved walkway around the pool.


Earl
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