CEE Rebar Stub Out? I don't think so.

[George Stolz]

For those that do not know CEE is short for Concrete Encased Electrode.

In my opinion it is a NEC violation to stub the rebar out of the foundation for connection to the GEC.

The facts as I see them.

250.52(A)(3) defines what a CEE is. That description requires that the CEE be surrounded by at least 2" of concrete.

Given that definition the rebar that is stubbed out is not a CEE. It is simply a steel conductor attached to the the CEE so in reality the stubbed out section is a GEC.

250.62 prohibits using steel as a GEC.

In my opinion and due to 250.64(A) the only legal way to connect to a rebar CEE is with a copper conductor connected to the rebar in the area defined by 250.52(A)(3).

All you 'stubbers' are in violation of the NEC. :grin:

I don't have time to read past page 2 of this thread, but I do have one thing to say - Bob, I won this argument already, and no fair firing it back up when I'm not around.

 

[cschmid]

oh please share with us your winning argument...

 

[e57]

come on!
~~~~~~~~
if the NEC didn't allow it , it wouldn' have included "accessible connection" and 250.68

Yeah!!!!!

On the "un-inspected stub-out" - beyond what some may feel about what this code says, compared to what it actually says - a short 12" piece of rebar tie-wired to a piece of rebar that leads to another piece of rebar that is it is tie-wired to that qualifies as the "electrode" could be OK... (Depending on who you talk to and what school of thought they are on.)

Lets call this one the "Knee bone connected to the leg bone" approach - all rebar is the electrode.... Not my usual practice or thinking - but I cant find anything to disallow it.

So far we can conclude the following about rebar: (Or at least I can... :grin: )

1. It can be one or more pieces tie-wired together in the usual manner and to make up this 20'. (One or more - tie-wired together suggests that anything tie-wired together is an extension of the "electrode" - no limit to the number of peices.)
2. It can make a little Escher type spiral consisting of a bazillion pieces and a whole roll of tie-wire at the bottom of their footing because the code says nothing about what direction, or that it be lineal.
3. A stub-out is an extension of the "electrode" because it needs to be accessible - as the exception is not the rule in 250.68

While the "knee-bone is connected to the leg-bone" approach is not my particular thinking on the matter (which would make any piece of rebar with tie-wire on it part of the electrode - which in many cases would be ALL of them) - there are no WORDS to the contrary in the code. And while any approach to this is subject to the AHJ - depending on their general mood and school of thought - because the code is ambiguous about the description of a CEE. From one of two extremes and anywhere in the middle could be considered an electrode. From a simple accessible clamp on any ol' piece of stubbed up rebar out of a footing or foundation - to single 20' straight stick of rebar exothermically welded to a GEC at the bottom of the pour.

IMO it is something that the code needs to clarify - I don't think that many people in the many camps could dis-agree with that? Let's just be careful about who does the clarifying...

 

[e57]

oh please share with us your winning argument...

Yes please do....

 

[e57]

We should also make no mistake that it it the concrete itself that is the "electrode" the connection to the steel is mearly a means of connecting to it.​

 

[volt102]

We should also make no mistake that it it the concrete itself that is the "electrode" the connection to the steel is mearly a means of connecting to it.​

And I have always thought that it was the re-bar, the concrete, and the contact with the earth - that made it an Grounding Electrode.

Take any one of those elements away and you lose the 'system.'

 

[tryinghard]

Yeah!!!!!

On the "un-inspected stub-out" - beyond what some may feel about what this code says, compared to what it actually says - a short 12" piece of rebar tie-wired to a piece of rebar that leads to another piece of rebar that is it is tie-wired to that qualifies as the "electrode" could be OK... (Depending on who you talk to and what school of thought they are on.)...(which would make any piece of rebar with tie-wire on it part of the electrode - which in many cases would be ALL of them) - there are no WORDS to the contrary in the code...

Well put! I will add the part that is not ambiguous is the #4cu being the electrode.

 

[cschmid]

so we are back to the fact that if you are not there for the pour then you can only assume that it is correct because you do not know what it is really like..so 2 rods make you legal and the stub out is just a possibility..I am sure only in the city does concrete get inspected..most rural areas have no inspectors for this..

 

[mivey]

And I have always thought that it was the re-bar, the concrete, and the contact with the earth - that made it an Grounding Electrode.

Take any one of those elements away and you lose the 'system.'

The buried concrete is more like a semi-conductor with a resistivity of 30-90 ohm-m (compared to 0.01 ohm-m for rebar).

This moist concrete provides a better connection between the electrode and the earth.

 

[mivey]

As for the tie-wiring:

Everyone must be aware of the fact that tie-wiring (20) 1 ft sections is inferior to having (1) 20 ft section. The smaller sections are bridged across a weak interface that has a much higher resistance.

These weak bridges are going to be an ideal spot for heating and vaporization of the moisture in the concrete during a high-current event and could lead to concrete damage.

The best method to join the sections would be to weld them.

 

[mivey]

As for the OP:
As much as it pains me to say it, iwire wins by TKO.:grin:

 

[crossman]

So:

If there is a job where the foundation and footings are using steel reinforcing rods that are coated with a non-conductive-epoxy, do you have to install some type of an electrode into the foundation before it is poured? Such as 20 feet of #4 copper?

Tryinghard, any comments?

 

[tryinghard]

So:

If there is a job where the foundation and footings are using steel reinforcing rods that are coated with a non-conductive-epoxy, do you have to install some type of an electrode into the foundation before it is poured? Such as 20 feet of #4 copper?

Tryinghard, any comments?

If the rebar meets all four elements of 250.52(A)(3) then it is a NEC electrode and 250.50 applies, if any one or all of the four elements are not present it is not an NEC electrode and 250.50 does not have to apply.

The #4 cu does not have to be installed in your scenario because any one of the seven listed in 250.52 can be instead. If in doubt installing the #4 as THE electrode qualifies the CEE as per 250.52(A)(3) even without the rebar.

 

[crossman]

Thank you for the reply. I wasn't sure if you understood that the #4 copper or a qualifying CEE isn't a mandatory requirement.

 

[cschmid]

okay I understand all of your points..I also do agree with Bob on this being a violation..

so the use of rear in concrete is because the assumption that concrete has a continual moisture level and is in contact with the soil..this then makes for a more consistent low level of resistance to the earth..Would that be a correct statement..

 

[cschmid]

I really hope allot of people are reading this..as there are some issue concerning this part of the code and I believe an amendment might be necessary..

this also is an area that needs to be addressed with building associations as it should include the electrical involvement in the footing area of the slabs..

I also think I have some more to add here..on this subject not that I am doing any more than sparing conversation on this issue because some here might make a good proposal because of it..

I have never done a proposal and might have to try one..

 

[mayjong]

if it is proposed to the NEC to NOT allow the connection of of the GEC to a "stubbed out" (or however you want to phrase it) piece of rebar , i believe it will fail. i would be interested to see the response, though!

 

[cschmid]

well I see several problems in the re-bar we are under the assumption that the concrete stays moist and creates a good connection with the earth..

When you use in concrete heating or under concrete (in ground) heating both dry out the concrete and the earth..so is the CEE still a good choice..who makes the call on when it is used and when it is not..

exothermic welding is now able to be perform on a simpler basis and more cost effective..so the connection point would be like a continuos piece of steel so would that make it legal after it protudes from the slab..

 

[crossman]

My take based on a thorough and literal reading of the code:

1. 250.52(A)(1) Waterpipe: The only part of a waterpipe that is the actual electrode is the part in contact with the earth. But the wording of the first sentence of 250.52(A)(1) allows the GEC connection to be made above ground as long as the point of connection is electrically continuous to the underground portion. The aboveground portion is just an electrically continuous connection to the place where the GEC is attached.

The second sentence is not saying that the aboveground portion of the waterpipe is still an electrode. It simply says the GEC connection cannot be more than five feet from where the pipe enters the building.


2. 250.52(A)(2) Building Steel: The entire building steel system is the electrode as long as any portion of it qualifies as an electrode within this section. So, it is okay to tie the GEC to building steel anywhere.

3. 250.52(A)(3) CEE: The electrode is only the rebar that is encased in at least 2" of concrete in the footing or foundation. If a rebar is stubbed out of the concrete, that portion of the rebar does not qualify as an electrode. And, this section makes no allowances for the extension of the electrode by something other than a qualified GEC as it does with waterpipes and building steel. Therefore, e rebar stubbed out of the slab is actually being used as a GEC and steel is not allowed for that.

4. 250.52(A)(4) Ground ring: no issues here

5. 250.52(A)(5) Rod and Pipe electrodes: The entire rod or pipe is considered as the electrode, even that portion that is extending above the ground. Of course, by 250.53(G), there has to be at least 8 feet in the ground. A ten foot rod could stick up 2 feet and the GEC connection could be made there. No problem because the entire rod or pipe is the electrode.

6. No need to discuss the other electrodes at this point.

 

[iwire]

Thank you for laying it out clearly and concisely.

I certainly agree with all your points.