250.52(A)(3) Concrete-Encased Electrode

[mivey]

Why is tying steel together to create a 20 foot electrode bad? The whole point of "bonding togeter with the usual steel tie wire" is to create a 20 foot minimum length of rebar.

It is allowed, but I consider it an inferior method. From CEE Rebar Stub Out? I don't think so.

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.

I don't see this as any different then assuming the re-bar installers have properly tied the bars. You do realize there are code rules regarding re-bar tyeing, they don't just 'wing it'. :smile:

They may have tied several sections together to make one 20 foot combined piece, and tied it to the fare-thee-well, but it will NEVER be as good as a 20 foot piece. But, according to the NEC, this inferior method meets code.

 

[iwire]

They may have tied several sections together to make one 20 foot combined piece, and tied it to the fare-thee-well, but it will NEVER be as good as a 20 foot piece.

I believe the discussion is focused on the code. :grin:

But, according to the NEC, this inferior method meets code.

Considering that a 4 AWG is the maximum size conductor required to connect the CEE to the premises wiring system it appears the NEC is aware that no matter how well made or installed there is only so much the CEE can do.

 

[mivey]

I believe the discussion is focused on the code. :grin:

Yeah, but I didn't feel like talking about that.:grin:

 

[tryinghard]

I am still serious, I don't care if the iron worker assebling a building frame knows he is installing an NEC electrode or not. It happens that he is...

In light of 250.52(A)(2) how so, what if he does not do what?s described in this section?

Now later when I install an SDS on the 10 th floor and connect that SDS GEC to building steel I do not go and inspect the each joint of the steel frame.

250.52(A)(2) has nothing to do with joints of steel frame, it does have to be effectively grounded with the correct size conductor. Do you know you cannot connect your SDS GEC to building steel unless the building steel is a qualifying electrode as per 250.52(A)(2)?

 

[mivey]

please clarify the point

please clarify the point

tryinghard,

I would like to see your point and its importance.

Are you saying that whatever a non-electrician installs is just a "something" until the electricians christens it an electrode, and that they really did not install an electrode but the electrician, by the christening process, actually "gets credit" for the electrode installation? Why is this important? What are you driving at?

 

[tryinghard]

tryinghard,

I would like to see your point and its importance.

Are you saying that whatever a non-electrician installs is just a "something" until the electricians christens it an electrode, and that they really did not install an electrode but the electrician, by the christening process, actually "gets credit" for the electrode installation? Why is this important? What are you driving at?

The electrode is an electrical item used for electrical purposes. The electrician needs to make sure it?s installed correctly. The NEC determines its application, and it?s the electricians? responsibility to apply all electrical components to NEC standards. It?s important that journeyman electricians install electrical items. There?s no christening involved.

Capiche :-? :roll:

 

[mivey]

The electrode is an electrical item used for electrical purposes. The electrician needs to make sure it?s installed correctly. The NEC determines its application, and it?s the electricians? responsibility to apply all electrical components to NEC standards. It?s important that journeyman electricians install electrical items. There?s no christening involved.

Capiche :-? :roll:

That would mean the journeyman electrician should make the installation of structural metal framing, footing re-bar, metal underground water pipe, non-gas piping systems, tanks, and well casings, etc.?

This can't be what you mean.

 

[cschmid]

Again size has absolutely nothing to do with it.

You could have a slab the size of Arizona and if it does not support a building or structure it is still not a footing or foundation. :smile:





Even slab homes usually have a stem wall that is supported by a footing.

Here is a slab on grade construction detail, the slab is slab and the part heading down into the earth is a footing.

Here is another that sounds a lot like your installation.

The footing is only at the perimeter so only the rebar in the footing can count as a CEE.

Pierre spelled it out



Also Pierre mentioned the vapor barrier that is often used under a slab.

It is my opinion that even without the vapor barrier under the slab that a slab, no matter how much rebar is in it will never qualify as an NEC CEE.

Bob nice illustrations and clarification..here we call them floating slabs..normally used on small single story houses or cabins..cost effective..

 

[tryinghard]

That would mean the journeyman electrician should make the installation of structural metal framing, footing re-bar, metal underground water pipe, non-gas piping systems, tanks, and well casings, etc.?

This can't be what you mean.

No electricians do electrical only; these items may become an electrode when they are effectively grounded. If they are not effectively grounded they are not an acceptable NEC electrode. The electrician only has to comply with NEC for each of these and do the electrical portion.

At least one of the seven electrodes must be used from 250.52, and if other NEC electrodes exist they must connect to each other. If the building frame is not effectively grounded meeting all the criteria of 250.52 & 250.104 it cannot be used as an electrode until it?s made effectively grounded with the correctly sized bonding jumper.

The same is true for the other electrodes, if the water pipe is not electrically continuous (for at least 10' in earth including the desired point of attachment not farther than 5' from its entrance to a building) it does not qualify as an NEC electrode and does not have to if another is used.

 

[mivey]

No electricians do electrical only; these items may become an electrode when they are effectively grounded. If they are not effectively grounded they are not an acceptable NEC electrode. The electrician only has to comply with NEC for each of these and do the electrical portion.

At least one of the seven electrodes must be used from 250.52, and if other NEC electrodes exist they must connect to each other. If the building frame is not effectively grounded meeting all the criteria of 250.52 & 250.104 it cannot be used as an electrode until it?s made effectively grounded with the correctly sized bonding jumper.

The same is true for the other electrodes, if the water pipe is not electrically continuous (for at least 10' in earth including the desired point of attachment not farther than 5' from its entrance to a building) it does not qualify as an NEC electrode and does not have to if another is used.

Are you saying these electrodes are not grounded until the electrician shows up?

 

[cschmid]

wow I read the entire post and the way I read this is that tryinghard is in firm belief that unless an electrician installs a conductive rod of at least 20 ft in the footings him self it does not count as a electrode..

If I am correct the steel is list as bonding to it not as a grounding electrode so re-bar being steel can be bonded but not classified as an electrode..

Am I correct on that interpretation of the reading tryinghard..

 

[cschmid]

Here in NY, we reference the 2002 NEC for dwellings and the 2005 NEC for other occupancies.

A couple of questions.

1. How many jurisdictions out there are enforcing 250.52(A)(3)?

2. If you are enforcing this section, how is it being performed?
a. via the building official during a footing inspection
or
b. the electrical inspector is performing the inspection.

Here there is a piece of re-bar stubbed out you use it and the electrical inspector inspects it..no re-bar drive 2 rods..and EI talks to GC or HO and tells them that in the future they need to provide one..

 

[crossman]

and EI talks to GC or HO and tells them that in the future they need to provide one..

The code wording does not really allow the EI to do that. Maybe a local ordinance?

Because the NEC does not say that a CEE electrode must be installed. The NEC says that if there is a qualifying CEE present, it must be tied into the grounding electrode system. So for an electrical inspector to tell the homeowner or general contractor that they MUST install a CEE is wrong.

There are lots of ambiguities here, and unenforcable code.

 

[crossman]

Okay, here is an example:
Electrical inspector meets the electrical contractor for final inspection of new residence:

EI: "I see you have the waterpipe electrode and a ground rod with less than 25 ohms to ground. But where is your connection to the CEE?"

EC: "I didn't make any connection for that."

EI: "That is a code violation."

EC: "No Sir it isn't."

EI: "It most certainly is."

EC: "No sir, before the foundation was poured, I looked at the rebar installation and it did not meet the requirements of 250.52(A)(3) so therefore I am not required to connect to it."

So... how does the electrical inspector know whether the electrician is telling the truth? Should the rebar have been used as a CEE? Was it a qualifying CEE by code? Does the electrical inspector need to inspect every foundation before it is poured so he can determine if there is a CEE present? He still cannot require a CEE to be installed.

The way it stands now, it seems that whatever AHJ inspects the rebar before the concrete is poured would have to determine if it was actually a CEE, and would have to make note of it and tell the electrical inspector about it so the electrical inspector could enforce the connection.

Should a bonding connection to the rebar be required in 250.104? Similar to the requirement for building steel? Even if the building steel is not a qualifying electrode, it still must be bonded to the service. I realize that there is much more chance for a fault to the building steel, and it may be a portion of the return path to facilitate tripping of breakers. Still, bonding to the rebar irregardless of its qualification as an electrode would ease the inspectors job.

 

[crossman]

This one is for TryingHard:

So far I have been arguing what the code says, not what it should say. My suggested remedy goes along with what you have been saying.

1. The NEC should require 20 feet of #4 Cu wire encased by 2" of concrete near the bottom of the foundation.

2. This #4 Cu should be bonded to the rebar regardless of whether the rebar is a CEE or not. All that rebar language could be removed.

It would be real easy to enforce all the above without having the ambiguities pointed out in my previous post.

 

[tryinghard]

wow I read the entire post and the way I read this is that tryinghard is in firm belief that unless an electrician installs a conductive rod of at least 20 ft in the footings him self it does not count as a electrode..

If I am correct the steel is list as bonding to it not as a grounding electrode so re-bar being steel can be bonded but not classified as an electrode..

Am I correct on that interpretation of the reading tryinghard..

I am an advocate of the electrician taking responsability for the electrode.

The footing rebar may be an electrode if it is installed as per 250.52(A)(3).

 

[cschmid]

Crossman I have heard the conversation and it did not go like that..

EI to GC the NEC has a requirement for a concrete encased electrode and it consists of and he explains the code section in detail and request that the GC to include this in his concrete plans so that the EL can bond to it..

GC said that seems easy enough to comply with and life goes on..

So that is real life here and I know tryinghard will not like that..

Yet at the same point I fully agree with trying hard that in order for it to be compliant the EI should either do the 20 ft or supervise it being done..

 

[tryinghard]

This one is for TryingHard:

So far I have been arguing what the code says, not what it should say. My suggested remedy goes along with what you have been saying.

1. The NEC should require 20 feet of #4 Cu wire encased by 2" of concrete near the bottom of the foundation.

2. This #4 Cu should be bonded to the rebar regardless of whether the rebar is a CEE or not. All that rebar language could be removed.

It would be real easy to enforce all the above without having the ambiguities pointed out in my previous post.

I agree, I think its easy to get roped into the emphasis or rebar steel taking precedence because 250.52(A)(3) spends the most wording on it. The part that is ambiguous is not so much what the steel electrode can be but where it is, what?s its parameters with regard to installing?

 

[e57]

I am an advocate of the electrician taking responsability for the electrode.

I usually make the sign of the X, and chuck some coffee at it - makes me feel better since I just crawled out the truck to wait for an inspector to do the same. I just cant get over framers who after you went through all that trouble to show up and wave your hand at it - then have the nerve to cut it off so they can put the sill plate on....

(Yes I have had idiots do that to #4 Copper too...)

Way to go Winner....

 

[iwire]

I am an advocate of the electrician taking responsibility for the electrode.

I am responsible to my connection to the steel that qualifies as an electrode. No more then that. :smile:

Here an electrical inspector has to sign off on that connection and at the same time they may well be looking to see that the rebar totals at least 20' just as I would have. :smile:

There is no need to go looking beyond that 20'.