Concrete Encased Electrode

[Cavie]

Rebar in concrete is not a CEE. It becomes one if you are installing a new service in new construction. The NEC does not require the rebar to be grounded to anything. It requires a new service to be grounded using the rebar if it is in contact with the earth. You guys are reading way too much into this.

 

[JohnE]

Cavie, what do you think of Wireman's analogy with the new water service?

 

[Cavie]

John, If that was true, the plumber would have to be a licensed electrican or call one to do the work. I think not. As stated, the NEC is not retro. Becides, the pipeing in the house is already bonded if it is copper. If not, it would be plastic and there would be no problem anyway.

 

[George Stolz]

...let's say you have damage on your concrete block basement wall due to frost...

The CEE is new, so you'd have to connect it to your GES.

The CEE is new, but is the structure "new" or "existing"?

The structure is existing, and is undergoing an alteration.

Your scenario also begs a philosophical question: If a CEE falls in the forest, and there is not an electrician there to hear it, is it a CEE? Or is it a chunk of concrete with some rebar in it?

The point I'm trying to illustrate is that grounding and bonding requirements for new construction don't imply a modification to the service - they only involve the grounding system.

Why is the addition in need of modification to it's grounding system? Do branch circuits require grounding? 250.24 states that a service does require grounding, and gives details. This addition only contains branch circuits and outlets, which do not require grounding per se.

They do require bonding, don't get me wrong. But they benefit little or nothing from 250.4(A)(1); as opposed to the requirements and benefits of 250.4(A)(3).

Until we dance with the service to this existing structure, I see no impetus to concern ourselves with grounding.

If I sound cocky or argumentative, I apologize. That's not the point of the exercise. I'm always trying to expand my knowledge, and in the rare instance where I think I can shed some light on a subject I'm not characteristically shy about sharing it.

Not at all, and likewise. You presented your case extremely well, I'm just not buying it.

 

[JohnE]

Boy, you guys are really swaying me. I may have to go back to my original stance. I need to think about this for a while. Maybe overnight. I've never felt so wishywashy on a topic before.

 

[dsteves]

Dan,

I think you've convinced me. But to be clear, the CEE needs to be part of the GES. However in the OP, if the GEC were inadequate, it would not be required to be addressed. The new CEE could be bonded to an existing ground rod, for example. Would you agree?

Hmmm. Let me start with the easier of the two items. The new CEE could be bonded to the GEC at the nearest grounding electrode as long as the connection meets the requirements of 250.64(C)(1), and the GEC at that point meets the requirements of 250.66 for size.

The other question requires a little more thought. If the existing GEC was undersized, I'd be inclined to replace the section between the proposed splice point and the original panel; alternatively, I'd remove the existing GEC and run a new one, properly sized, from the CEE to the original panel. The Code recognizes the CEE as sufficient as the sole electrode required to supplement the metal underground water pipe. See 250.53(D)(2). So, you could meet requirements and actually remove the non-compliant EGC and the (presumably) rods it ran to. If you chose to do that, you'de have to remove the rods too, but I think more is better, so I'd probably leave the rods and resize the GEC. I honestly feel that if the old GEC was undersized according to the Code in effect at the time of installation, I would fix it.

I think you could possibly "get away" with not touching the old GEC if you don't disturb it or use it to connect a new electrode, but I don't think that's the right thing to do. The only exception I can think of would be that the EGC was sufficient at the time of installation, but no longer meets size requirements. Then I'd leave it alone and install a new GEC between the panel, the water pipe and the CEE. Ignoring a wrong doesn't make it right.

George, I've got the National Electrical Code Handbook 2005 by Earley, et. al. open to page 207. I'll quote the explanation of 250.50 here.

[begin quote]
Section 250.50 introduces the important concept of a "grounding electrode system", in which all electrodes are bonded together, as illustrated in exhibit 250.21. Rather than total reliance on a single grounding electrode to perform its function over the life of the electrical installation, the NEC encourages the formation of a system of electrodes "that are present at each building or structure served." There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time.

This section was revised for the 2005 Code to clearly require the inclusion of a concrete-encased electrode, described in 250.52(A)(3), in the grounding electrode system for buildings or structures having a concrete footing or foundation with not less than 20 ft of surface area in direct contact with the earth. This requirement applies to all buildings and structures with a foundation and/or footing having 20 ft or more of 1/2 in. or greater electrically conductive reinforcing steel or 20 ft or more of bare copper not less than 4 AWG. However, an exception does exempt existing buildings and structures where access to the concrete-encased electrode would involve some type of demolition or similar activity that would disturb the existing construction. Because the installation of the footings and foundation is one of the first elements of a construction project and in most cases has long been completed by the time the electric service is installed, this revised text necessitates an awareness and coordinated effort on the part of the designers and the construction trades in making sure that the concrete-encased electrode is incorporated into the building grounding system.

[end quote]

Now, with that said, if you modify an existing structure or build a new one, and in either case put in a new CEE, it's clear to me what the Code requires. Additionally, if I were the AHJ and thought someone forgot to connect the new CEE, I'd make the contractor expose the CEE and bond to it. If you are voluntarily modifying the existing building or structure, and either expose existing CEE or install a new CEE, there you are.

The CEE in the forest is rebar in concrete until you put a building or structure around it and provide electric service to the building or structure. If the man is alone in the woods and a tree falls next to him, his wife will say he is *still* wrong.

In order to understand 250.4(A)(1) and how that relates to the GES, it helps to understand that parallel conductors have a mutual impedance, and that low Z is good for limiting the magnitude of transients. The conductors don't have to be connected together to enjoy impedance. Parallel impedances are vectorially diminishing overall impedance. You have line and grounded (and even grounding) conductors in parallel for every branch circuit in the building or structure. This massively parallel impedance system will not effectively limit transverse-mode transients unless the series impedance system involving the building GES and the branch circuit wiring (through the bonding jumper) can have parallel impedance circuits between the bonding jumper and the earth. The more elements in the GES, the lower the impedance.

Cavie, the rebar *is* the path to ground; it doesn't need to be grounded. If it's an electrode, and it is encased by concrete, it is by definition a concrete-encased electrode. The bonding requirement to the water pipe is within 5 feet of its entry point into the building, with little exception. If you're repairing the plumbing in that area, the electrician should have already bonded over the valves and the meter; or if you're installing the plumbing in that area, the building plumbing is new and the electrician will be there someday to bond it.

John, go have a few beers and think about it. I will.

"I've cut it three times and it's *still* too short!"

Dan

 

[George Stolz]

I've never felt so wishywashy on a topic before.

That's not hard on this topic. There is no right or wrong.

 

[tbonse]

IMO, all new work should meet all current codes. That being said, lets say you have an existing house and are adding another room, and for the sake of argument it is a bedroom with a basement extension underneath (so that it encompases the current discussion).

I feel you would then need to put that new bedroom on an AFCI, though you wouldn't need to change the other bedrooms (yet). Now when you get to the panel to install the AFCI breker, you find that the panel that exists can't handle an AFCI (for whatever reason, space/manufacturer...). Well now you would need to replace the panel and upgrade other parts of the electrical system to match current code.

Second scenario, you could put in the new AFCI. So you put in the new AFCI for the new bedroom, since you have new work in an old structure, and the new work must meet current code. Lets also say that you are using reinforced concrete to form the new foundation, then by the same token as the AFCI, the rebar needs to be bonded with the EGC for the structure. The only loophole I could possibly see for not having to do this bonding is if you are not extending ANY electrical into the NEW portion of the structure, which I find highly unlikely/impractical. So I guess I do agree with the inspector.

Now I would say that it was the responsibility of not only the general contractor and the sub who was pouring the concrete, but also the Electrical sub, to make sure that the rebar was ready for the pour (including the EGC being run into the concrete and bonded to the rebar) before pouring any of the concrete. As for you not being contracted for the electrical work till after the concrete was poured, does not mean that it doesn't still need to be bonded (b/c it is new work). It may however mean that your bill for the work may be larger (more man-hours) and that some of the concrete will have to be patched. I say that is the price for the General Contractor not knowing what has to be done to complete the job and for not talking to his/her subs ahead of time. The same would be true for the plumbing if a drain had to be run under the cement floor, but wasn't stubbed out ahead of time. The floor would still have to be cut into and the plumbing run, and at a higher price than if the work had been done when it should've been. And I agree it is easier and cheaper to do it right the first time than to have to fix it later.

 

[Cavie]

Tbonse, This is where you are missing the point. The code does not say that the rebar must be bonded. The code says that the rebar must be used as a cee "IF" you are building a service.

 

[iwire]

Now I would say that it was the responsibility of not only the general contractor and the sub who was pouring the concrete, but also the Electrical sub, to make sure that the rebar was ready for the pour (including the EGC being run into the concrete and bonded to the rebar) before pouring any of the concrete.

The EC never under any NEC rule has to install rebar.

If the footing do not have rebar than they are not concrete encased electrodes and therefore the EC does not have to make a concrete encased electrode.

BTW you do not run an EGC into the cement pour, if your run a conductor into the pour it will be a GEC.

 

[iwire]

The code says that the rebar must be used as a cee "IF" you are building a service.

IF a concrete encased electrode is available, I do not have to install rebar to make one if there is no rebar planed for the footings.

 

[Cavie]

Yes Bob that is correct. But in Florida, there IS rebar in it if it is a footing. Except maybe a flat slab for a screen porch. In 2005, you WILL use it because it will be PRESENT.

 

[iwire]

Yes Bob that is correct. But in Florida, there IS rebar in it if it is a footing.

Is this a FL only or a National forum?

All I am asking is to be clear when posting that you may be speaking only about your area.

Here in my area if you don't get a concrete encased electrode connected before the pour on a new building you may be breaking cement to get it after.

 

[Cavie]

We are still working on the 2002 in Florida, so if the steel is not "Availible" as in poured, you can drive 2 ground rods. In 2005 the code says "If present" so if you miss it, you get out the jack hammer. Should have the 2005 in December but still have not heard the form the officials. I took the info on the adoption given to me by BHgravity, but have heard nothing. I am pretty shure that in all of Florida, if it is called a FOOTER, it will have some rebar in it. I may be wrong and never afraid to admit it.

 

[roger]

This is where NC saw a problem with the 05 wording and amended it to the 02 wording.

NORTH CAROLINA ELECTRICAL CODE, 2005 EDITION AMENDMENT 250.50
Delete NEC 2005 text and replace with:
250.50 Grounding Electrode System. If available on 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. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.

Roger

 

[Cavie]

Why would NC want to make a code that in LESS stringent the the NEC? They just beefed it up in 2005 and NC knocked it back down. After one or two hamerjobs, nobody will forget to install at the pour so there will be no hardship. the concrete boys can be trained, they really can. In Sw Florida the structual inspector looks for a painted green rebar sticking up.

 

[dsteves]

Tbonse, This is where you are missing the point. The code does not say that the rebar must be bonded. The code says that the rebar must be used as a cee "IF" you are building a service.

I was at a Halloween party last night. I just got up. The coffee pot is spewing. First, Cavie, quote me the part where "building a service" comes into play.

Now, everybody get out your books and turn to 250.52(A)(3).

Note that there is no black bar running vertically on the left side of that paragraph. That indicates the paragraph has not changed at all since the 2002 code. So, we've had 4 years, at least, to learn that a CEE is:

1. Located within and near the bottom of a concrete foundation or footing
2. The concrete in (1) is in direct contact with the earth
3. The length of the electrode is 20 ft or longer
4. It's made of some form of coated conductive steel at least 1/2" in diameter, OR it's made of bare copper of at least #4 AWG

Not in floor, not in wall. Foundation or footing, no vapor barrier, no insulation.

Ready?

Turn to 250.50. It's one page back. Notice the black bar running down the left side of the paragraph - ALL of it. That means the ENTIRE paragraph was rewritten in the 2005 Code. So, we all have the excuse that *this* is only 1.824 years old, as of today, so we haven't had time to get our heads around it. (Somebody had better check my math on that - first pull off the coffee.)

The paragraph is two sentences long. It is a long sentence pair, and linguisticians would say it's too long for the average population. They may be right.

I'll deal with the long single-sentence exception later. First, let's break down the first sentence.

A.
"All grounding electrodes as described in 250.53(A)(1) through (A)(6)..."

The CEE I defined at the beginning of this posting is 250.53(A)(3). That is between (1) and (6), so it applies.

B.
"... that are present at each building or structure..."

This means that if the building or structure in question contains the thingy in 250.52(A)(3)

C.
" ... served ..."
This means the building or structure either has electrical service or will have it shortly.

D.
"... shall be bonded together to form a grounding electrode system."

Seems clear enough. What about the second sentence? Maybe that's the problem.

E.
" Where none of these grounding electrodes exist, ..."
Remember we're talking about the thingies in 250.52(A)(1) through (6).

F.
"... one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(7) shall be used."
I thought about breaking this one in two, to emphasize "one or more", but let's press on. The concrete-encased electrode is 250.52(A)(3). So, if it doesn't EXIST, you don't have to make one. This is because the second sentence only requires one or more of (A)(4) through (A)(7), which *doesn't* include (A)(3).

The exception must be the problem. So far, all is clear.

"Exception: Concrete-encased electrodes..."
Jackpot! The exception is CEE's! Whoopee!
" ... of existing buildings or structures..."
You see, the building or structure is already here, so I'm exempt!
"... shall not be required to be part of the grounding electrode system..."
That's it. Am I still typing? Let it go, for God's sake.
"where the steel reinforcing rods are not accessible for use..."
If I cover them up fast enough, they won't be accessible.
"without disturbing the concrete."

OK. Now, if you intentionally disturb the concrete and expose the CEE as painfully and protractedly defined in this and earlier posts, guess what? The execption *doesn't* apply. I also submit that in new construction (which includes modifying old construction, ladies and gentlemen) if the trades don't play well together, and cement head covers up the CEE before Sparky gets there, *someone* has dropped the ball, probably the GC. The other possibility is a "screw the other trades" attitude, which besides being unprofessional leads to a Code violation in this instance.

If you build a utility shed and put #5 rebar in the footings, and you have more than 20 feet of rebar, essentially meeting the definition of 250.52(A)(3), but you never plan to electrify the utility shed, knock yourself out. There is no requirement to do anything in that instance. You don't need to do a thing.

If you come back 10 years later and put an outlet in for lighting, you *still* don't have to use the CEE, by exeption, because you'd have to ding up (sic) the existing concrete to get to it.

If you're building a new building or structure now and plan to electrify it, *and* CEE meeting the requirements of 250.52(A)(3) exists, YOU MUST USE IT and see to it that bonding means are made prior to encasing the electrode with concrete. Period.

"Ignorance of the law is no excuse." - Unknown
"I'm tryin' to think but nothin' happens." - Curly Howard

Dan

 

[iwire]

Why would NC want to make a code that in LESS stringent the the NEC?

Perhaps NC is questioning the importance of any particular electrode?

In other words if you missed the chance at a CCC you can always use the electrodes we have used for years that have done the job.

Whatever job that may be, I am not really sure one electrode will do anymore than another.

 

[roger]

NC saw where this was simply unnecessary, so if it is not available there is no reason to worry about it.

As far as the NEC requirements always being better when they are made more stringent from one cycle to another, it's not always true, for example, look at 384.2 of pre 93 cycles and compare it to modern 110.26 requirements.

In some circumstances it goes the other way when the CMP's see there was no need for a certain requirement in the first place.

Roger

 

[roger]

Morning Bob.

Roger