Rebar in walls

[ptonsparky]

In the 2008, the rebar in the basement wall will likely be considered a CEE in it's own right, according to the language from the ROC:


Quote:
2008 250.52(A)(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2in.) 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 220 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 (1/2 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.
__________________
I copied this from another thread and had to sleep on it a week or so. Until this morning about 4 am actually.

All basement walls in the area are either tarred of othewise waterproofed, the footings are the only thing that would have direct contact with the earth. On larger commercial jobs you will see rebar extending up from the footing, but not on residential. Will this design exclude using the rebar in walls as a grounding electrode?

 

[raider1]

All basement walls in the area are either tarred of othewise waterproofed, the footings are the only thing that would have direct contact with the earth. On larger commercial jobs you will see rebar extending up from the footing, but not on residential. Will this design exclude using the rebar in walls as a grounding electrode?

This is a good question,

I feel that if you have dampproofing or waterproofing applied to wall you probably don't have direct contact with the earth and can't use the rebar in the wall as a grounding electrode.

I would love to hear what others think of this situation.

Chris

 

[don_resqcapt19]

Tom,
I don't see how the rebar in the wall is a grounding electrode. A wall is not a footing or foundation. Only the rebar in a footing or foundation is to be used as a grounding electrode.
Don

 

[tkb]

Isn't the foundation, the walls that sit on the footings?

 

[don_resqcapt19]

Tim,

Isn't the foundation, the walls that sit on the footings?

yes...I don't know what I was thinking.
don

 

[ptonsparky]

To clarify, I am thinking of the poured concrete that would typically be the perimeter wall of a basement.

 

[gndrod]

In the 2008, the rebar in the basement wall will likely be considered a CEE in it's own right, according to the language from the ROC:


Quote:
2008 250.52(A)(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2in.) 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 220 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 (1/2 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.
__________________
I copied this from another thread and had to sleep on it a week or so. Until this morning about 4 am actually.

All basement walls in the area are either tarred of othewise waterproofed, the footings are the only thing that would have direct contact with the earth. On larger commercial jobs you will see rebar extending up from the footing, but not on residential. Will this design exclude using the rebar in walls as a grounding electrode?

Hi Tom,

If this is the exact wording from the final ROC accepted wording, then I believe they have somewhat shot themselves in the 'footer'. The word "vertically" will cause problems to electricians when they find out that the vertical rebar 'risers' are #3 rebar which is not 1/2" in diameter. Only spec'd stemwall design for #4 (1/2") or larger will be acceptable. Stemwalls that are retainer or engineered use rebar specified larger than #3. This could be something to watch out for when chosing a foundation electrode.

 

[infinity]

IMO the more important part of the requirement is the last sentence:

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.

This will end the nonsense of having to bond separate 20' sections of rebar together or use more than one 20' section of rebar. Some have suggested in the past that this is required.

 

[George Stolz]

Suppose the footer rebar was tied to the foundation wall rebar, and the foundation wall rebar was the minimum size. Is this not one giant electrode, as opposed to two smaller ones?

Suppose the footer is exposed, yet the foundation walls are waterproofed; then the GEC connection to the vertical wall, which is acceptably connected to the footer would still be compliant, wouldn't it?

A waterproofed vertical wall alone would not comply with 250.52(A)(3), but an interconnected system with the footer providing the earthing connection would be acceptable, no?

 

[don_resqcapt19]

Trevor,

This will end the nonsense of having to bond separate 20' sections of rebar together or use more than one 20' section of rebar.

Is it really nonsense? Read Bryan's post in this thread.
Under the conditions described in Bryan's post would there not be significant potential between the bonded and non-bonded sections?
Don