# Rebar in foundation grounding



## Shockdoc (Mar 4, 2010)

a DB rated rebar or rod clamp & #6 cu


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## RKRider (Feb 7, 2010)

#4 awg

250.52(3)(2)


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## carryyourbooks (Jan 13, 2010)

Shockdoc said:


> a DB rated rebar or rod clamp & #6 cu





RKRider said:


> #4 awg
> 
> 250.52(3)(2)


uno.


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## McClary’s Electrical (Feb 21, 2009)

carryyourbooks said:


> uno.


 
Cut him some slack, he hasn't touched a code book in 4 months


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## HARRY304E (Sep 15, 2010)

mikewardjr said:


> Ok so I have to bond the foundation in an addition. I haven't done this before. Any recommendations on how I should do this? I know I need a grounding lug rated to be encased in concrete.


250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.

(3) Concrete-Encased Electrode. A concrete-encased
electrode shall consist of at least 6.0 m (20 ft) of either
(1) or (2):

(1) 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, installed in
one continuous 6.0 m (20 ft) length, or if in multiple
pieces connected together by the usual steel tie wires,
exothermic welding, welding, or other effective means
to create a 6.0 m (20 ft) or greater length; or

(2) Bare copper conductor not smaller than 4 AWG
Metallic components shall be encased by at least
50 mm (2 in.) of concrete and shall be located horizontally
within that portion of a concrete foundation
or footing that is in direct contact with the earth or
within vertical foundations or structural components
or members that are in direct contact with the earth.
If multiple concrete-encased electrodes are present at
a building or structure, it shall be permissible to bond
only one into the grounding electrode system.
Informational Note: Concrete installed with insulation, vapor
barriers, films or similar items separating the concrete
from the earth is not considered to be in “direct contact”
with the earth.


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## Sencoman (Nov 27, 2011)

HARRY304E said:


> 250.52 Grounding Electrodes.
> (A) Electrodes Permitted for Grounding.
> 
> (3) Concrete-Encased Electrode. A concrete-encased
> ...


 
It says foundation or footing, no mention of slab. So bonding to rebar in a slab doesn't meet code?


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## Magnettica (Jan 23, 2007)

mikewardjr said:


> Ok so I have to bond the foundation in an addition. I haven't done this before. Any recommendations on how I should do this? I know I need a grounding lug rated to be encased in concrete.


Be sure this grounding electrode conductor is run to the main disconnect and bonded to system grounded conductor.


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## HARRY304E (Sep 15, 2010)

Sencoman said:


> It says foundation or footing, no mention of slab. So bonding to rebar in a slab doesn't meet code?


Yes it will just in another section of the code.


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## John Valdes (May 17, 2007)

I wonder if you need to ground to the re-bar on a renovation/addition? If the structure is already bonded/grounded, why not use an EGC and forget about the GEC. After all, you have an existing grounding electrode system already? Right?
Be more specific regarding "addition".


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## dronai (Apr 11, 2011)

HARRY304E said:


> 250.52 Grounding Electrodes.
> 
> *Informational Note: Concrete installed with insulation, vapor*
> *barriers, films or similar items separating the concrete*
> ...


 



Sencoman said:


> It says foundation or footing, no mention of slab. So bonding to rebar in a slab doesn't meet code?


The slab usually has a vapor barrier under it for moisture. This would separate the concrete from the earth. I would think the footing is where you have to be.


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## macmikeman (Jan 23, 2007)

Magnettica said:


> Be sure this grounding electrode conductor is run to the main disconnect and bonded to system grounded conductor.


It can also be run to an interior section of h20 pipe and bonded to that where that is a qualified gec that is bonded back to the service disconnect within 5 foot of where it enters the building. Go have a look at the Mike Holt section 250-50 gec illustration. The uffer ground is a supplementary means.


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## macmikeman (Jan 23, 2007)

John Valdes said:


> I wonder if you need to ground to the re-bar on a renovation/addition? If the structure is already bonded/grounded, why not use an EGC and forget about the GEC. After all, you have an existing grounding electrode system already? Right?
> Be more specific regarding "addition".


There is an exception for existing structures in the nec. Where that might fly out the window is if you are replacing the existing service entrance due to it might be in the way of the new addition and you need to relocate it someplace else. In that scene we are required here at least , to run an uffer if the new addition footing rebar qualifies for a gec.


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## Magnettica (Jan 23, 2007)

macmikeman said:


> It can also be run to an interior section of h20 pipe and bonded to that where that is a qualified gec that is bonded back to the service disconnect within 5 foot of where it enters the building. Go have a look at the Mike Holt section 250-50 gec illustration. The uffer ground is a supplementary means.


I disagree with that based on how the code is written. The Ufer ground (concrete encased electrode), is required if it's available. It is NOT supplementing anything, it is required.



> 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
> ...


If it is not available, then anyone one of the following can be used.



> 250.52(A)(4) Ground Ring. A ground ring encircling the building or
> structure, in direct contact with the earth, consisting of at
> least 6.0 m (20 ft) of bare copper conductor not smaller
> than 2 AWG.
> ...


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## macmikeman (Jan 23, 2007)

Magnettica said:


> I disagree with that based on how the code is written. The Ufer ground (concrete encased electrode), is required if it's available. It is NOT supplementing anything, it is required.
> 
> 
> 
> If it is not available, then anyone one of the following can be used.



I don't know what version of the nec your on, but 05 was the last time they had that word in that section. It changed to "if present" in 08. That means it has to be used if its there, available or not. But there is an exception for existing structures like I mentioned above.


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