Slab for concrete encased electrode

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Desert Spark

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I'm running a new service to a well house that is a pre-fabbed, tough shed type structure, about 8' x 12', 2x4 framing.

I was sent to the job after the slab was poured and the shed already in place. The approved plans I was given called for a concrete encased electrode with 20' of #4 copper encased. Since we were on site after the fact I just went ahead and drove two ground rods.

It's about a 4" slab with no footing, poured on a gravel base. Would a CEE even be acceptable in this situation? The code says metallic components must be located horizontally in a foundation or footing in direct contact with earth.

I was browsing through some other posts on grounding electrodes and discussions on if they are available you have to use them and made me think of this. I don't know if the inspector will say that the ground rods are not on the prints and why wasn't the ufer installed, but I was just trying to see that if he did, I could simply say that the slab doesn't meet the requirements anyway.

Also on the topic, what if you arrive on a job that meets all the parameters for having a CEE, but there is not copper ran or rebar stubbed up to make the connection? Say someone put up a metal building and then hired an EC later and there was not a chance to get it done. Does that mean that the CEE exists, and you have to somehow make the connection, or could it fall under the exception for existing buildings or structures?

Thanks for any info.
 
The results will vary by individual AHJ and inspector, but technically if a CEE existed (qualifying rebar in qualifying foundation or footer, not just slab) at the initial electrical installation and it was not connected to, that is an existing violation if a CEE was required under the NEC cycle applicable at that time.
Violations at install are not grandfathered in and would have to be corrected if you are pulling a permit.

Some AHJs may choose not to enforce this though.
 
Cool, thanks for the replies. I guess I never thought much about the requirement of having to use a CEE. I always looked at it as not existing as an actual electrode until you made it into one by having some rebar or #4 stubbed out. I don't think I've worked on any new construction without them, I'm sure in most cases they are a better grounding electrode.

Just thought that maybe thats the way they were spec'd out but on smaller structures you could just show up late and drive some ground rods and be ok.

So thanks to you and the forum for the clarification! I'm sure somewhere down the road that could've caused me some headache.
 
Good point. I guess what I had thought is that if whoever was doing the concrete could 90 some rebar and follow the perimeter it would be ok, since the code allows the rebar to be wire tied together. If this slab actually had a footing I think it would be good to run it in there that way. To be on the safe side I would probably just tie some #4 copper onto the rebar and run it around the footing that way.
 
Adamjamma said:
doesn't it also call for the rebar to be 20 foot continuous: which is not possible if slap is 8 by 12?
Click to expand...

You can tie 20-1' pieces together if you want to get the 20' required. It does not need to be a 20' continuous piece.
 
The National Electrical Code (NEC) requires that all normally non-current-carrying metallic objects in a given structure be bonded together to form a single common system that is at the same potential. This includes the steel rebar in the concrete foundations. We see in Article 250.50 the mandate that all electrodes listed in the code (steel rebar in concrete can sometimes qualify as an electrode) be bonded together, whether they are used as an electrode or not.
In the case of steel rebar in concrete, we see in 250.52(A)(3)(Information Note) that epoxy coated rebar and/or a vapor barrier can negate our ability to use the rebar as an electrode, however our mandate to bond the systems to form a common system still remains under 250.50. In other words, you must bond the steel rebar in concrete foundations whether you use it as an electrode or not (just like a water pipe, gas pipe, alarm system, fire sprinklers, CATV, Telco, etc).
Please see the NEC 2017 Handbook Exhibits: 250.22, 250.23, 250.29, and 250.30.



so the use of rebar at least 20 foot long does not mean that?
 
The CEE needs to be 20' in length and can be made of short sections of rebar tie wired together it does not need to be one continuous piece.

250052(A)(3) Concrete-Encased Electrode. A concrete-encased elec-
trode 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 electri-
cally 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
Click to expand...
 
After reading 250.52 (A)(3) more closely, the way I interpret it is that the rebar is not required to be part of the CEE. You can just run 20' of bare #4 copper in a footing and now its a CEE. It never says that it has to connect to the rebar. Correct me if I'm wrong but I don't think the code requires rebar to be bonded if not for the purpose of a CEE? It doesn't seem like it would be necessary like it would for a metal piping system, or building steel, etc.

At the end of 250.52 (A)(3) it states that if multiple CEE's exist, it is permissible to bond only one into the GES.
 
ok.. had never seen that section when looking at it... Of course, I only have an old copy of regs... pre 2000...lol.. everything else I know comes from reading sections online...or the british codes
 
Desert Spark said:
After reading 250.52 (A)(3) more closely, the way I interpret it is that the rebar is not required to be part of the CEE. You can just run 20' of bare #4 copper in a footing and now its a CEE. It never says that it has to connect to the rebar. Correct me if I'm wrong but I don't think the code requires rebar to be bonded if not for the purpose of a CEE? It doesn't seem like it would be necessary like it would for a metal piping system, or building steel, etc.

At the end of 250.52 (A)(3) it states that if multiple CEE's exist, it is permissible to bond only one into the GES.
Click to expand...

You're correct. If the rebar is present and qualifies as a CEE then you need to use a CEE, however the CEE can be either the rebar or 20' of #4 or larger copper conductor.
 
It's not for me. I have a better understanding of what actually constitutes a CEE. Originally I was thinking that a CEE could have been possible if I was there before the slab was poured, in the given situation in my OP.

And, thanks for the suggestion about the well casing, although where I'm at now it's PVC, I'll be aware of that next time.

Appreciate the feedback!
 
If it is present and qualifies as a electrode you must use it. If there is qualifying reinforcement in the footing it must be used, if there is qualifying metal water piping it must be used, if there is qualifying structural steel it must be used. Most other items that qualify as an electrode are intentionally put there to be used as an electrode.

Well casing - generally is outside at separate structure so not required to be used as an electrode for another structure. May not be a bad idea to connect to it though, especially if near structure in question.
 
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