20' of 4 AWG bare copper

[websparky]

I am trying to understand the logic of requiring us to connect to the rebar in a footing when 250.52(A)(3) gives us the option of "or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG." to qualify as a concrete encased electrode.
In other words; Could we not accept the 20' piece of copper layed in a footer along side of the rebar and not connect to the rebar? Why does a typically shorter piece have to be connected to the rebar via an approved clamp? Why do we have the impression that rebar MUST be connected to in the first place? Read 250.50 with out any prejudice or preconceived attitudes and see if you can see where we MUST connect to the rebar. Remember, rebar is ONE of the options listed in 250.52(A)(3) as an acceptable concrete encased electrode.

 

[iwire]

Re: 20' of 4 AWG bare copper

Big debates about this subject.

I take the 5th on this one

Here is one of the longer discussions

Uffer

 

[jwelectric]

Re: 20' of 4 AWG bare copper

Dave
I admit that I was at one time convinced that if the rebar was there it was REQUIRED to be bonded a number 4 AWG copper conductors as part of the electrode system or the earth would stop spinning.
After a lot of consideration and studding of the wording of 250.50 I have changed my mind.

The wording in 250.50 that is confusing people is, All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present.
I can see here that all of the electrodes including (A)(3) the concrete encased electrode if present MUST be included but what is a concrete encased electrode?

(3) Concrete-Encased Electrode An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom 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 ( 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.

In the quote of section 250.52 (A)(3) above I have highlighted with bold type an alternate electrode to the rebar as outlined in that section.
I contend that as long as the concrete electrode weather the rebar or the #4 is used as outlined in 250.50 the requirement of the code is fulfilled. If both are present ONLY one need to be used.

 

[bphgravity]

Re: 20' of 4 AWG bare copper

I am ounder the opinion that either or can be used. As stated above, if prsent, the concrete encased electrode must be used. What should it matter if it is rebar, copper, or both.

If the contractor wants to take advantage of the rebar that will already be there, good enough. If the contractor wishes to create their own with #4 copper, good enough.

One could argue that using only the copper leaves a present electrode consisting of rebar, but I think it is all one big system.

 

[benaround]

Re: 20' of 4 AWG bare copper

In most of the buildings I work on, they have re-rod tied together including all the steel columns,the slab,the footer,and walls.
For the sake of an Acorn Clamp, why would you not take advantage of such a good system?