Ufer Grounding and Visqueen????

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Palmbay

Palmbay

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Palm Bay Florida
Hello all this is my first topic. Very informative site.

I have been an Electrical Contractor for a little over a year now in Florida.

Last week I went to a new residential job, to install a grounding electrode conductor to the rebar in the slab prior to pour and inspection. Before I left the inspector showed up so I walked through the site with him as did the contractor. When he got to the ground he informed me that the #4 insulated conductor, connected to the rebar by a dirrect burial grounding clamp was insufficient. According to him I needed to have 20 feet of insulated wire run in the slab and then connected to the rebar. Well I asked for a code reference, and he could not tell me the specific code reference but he did tell me that he would call me and let me know specificly. Well the contractor was looking at me like, what are you doing. So I did exactly what he wanted to keep everything smooth. At that point the inspector turned his attention to the contractor and I decided to make the requested "correction". Then I left.

Today I spoke with the contractor and through the corse of the conversation he told me that inspector made him install visqueen under all of his footings.

I now wonder what the point of any rebar grounding was.

And then I wonder what will happen to that slab when the house gets hit by lightning and the ground rod can't handle it????

Love to here what you all have to say about this.

Mike
 
Some have argued that, without the footing in direct contact with the earth, that a concrete encased electrode is not required. The requirement is for the footing to be in contact with the earth. I don't see how this is possible if it's sitting on a layer of insulating material.
 
I agree.

First of all the 20 feet of insulated wire??? Not doing anything, and not required.

Second is the Visqueen is not allowing the concrete to be in contact with earth.

Basically the grounding system will be unsulated from the ground.

It concerns me. I am thinking of going to the building department and having a chat with AHJ.

I have heard of swiming pool slabs exploding from lightning strikes. This seems like it might be setting up to be that sort of situation. Correct me if I am wrong.
 
Sounds like the inspector is confused about CEE's. If you can't get anywhere with him, a chat with his boss may be in order.
 
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Agreed. Before it comes to that, do a search for "Ufer", "CEE" and "Concrete Encased Electrode", and you will find many conversations on this topic - if the search feature is working correctly by now.
 
Being that this is FL, the inspector may not be as qualified as many helpers. (There are exceptions though, read Bryan Holland for one)

Roger
 
infinity said:
Some have argued that, without the footing in direct contact with the earth, that a concrete encased electrode is not required. The requirement is for the footing to be in contact with the earth. I don't see how this is possible if it's sitting on a layer of insulating material.
Click to expand...

I don't have access to my code book (still home now). Does the code say the footing must have contact to earth on the bottom of the footing, or just contact to earth?

If the visqueen is under the footing, the sides of the footing still have contact with earth.
 
The inspector is probably getting confused with, excuse me if not perfect I don't have my code book with me, the part that says 20' of wire in a ground ring needs to be bonded. That will still be uninsulated. Not sure where he is getting the insulated part from.
 
Bob P., here it is:
(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.
Click to expand...
The concrete must be in contact with the earth to serve as a grounding electrode.
 
Palmbay, welcome to the forum.

I'd say that a footing with it's side in contact with the earth qualifies as a CEE.

Are you sure inspector said 20' insulated #4, not uninsulated? If he said insulated, good luck with other issues.

John
 
Although it's not electrical, I'd like to hear Bryan's take on the visqueen under the footings.

We do that here, along with epoxy coated rebar because of corrosive soil conditions. It is based on a soil engineer report.

Does Florida have corrosive soil in some areas?
 
We have researched this issue to death and still have conflicting information on the issue.

To start with, I think the whole lightning blowing up the slab is a little over exaggerated. I know it has happened, and I'm sure it can happen, but I don't think it should be a primary concern - or at least enough of a concern to not use a CEE.

I can positively say that the FBC/FRC does not require the vapor barrier to extend into the footer. Most of the time this done to prevent washout and to help hold the form. That being said, the County of Sarasota commissioned an engineering firm to test GES resistance of various electrodes a few years back. I don't have an official copy of the report (yet), but I do believe it indicated that even with the vapor barrier under the concrete, the electrode had a lower resistance versus two ground rods. Oddly enough.

We agree that the sides of footings are in contact with the earth, and we also agree that a 20' section of the plastic removed from the footer will provide the sufficient earth contact as required by the NEC. Then again, we allow the contractor to stub up rebar out the footing into an open cell or interior wall which I question as being code compliant.

When it is all said and done, I don't really put all that much concern into the GES at typical structure. Though ground rods have shown to be very useless, they are still permitted by the code. And if by chance the contractor misses the connection to the CEE before the pour, I am not going to lose sleep over it.
 
Great replys, Thank you.

The contractor was telling me that there is a requirement for exposed copper in the pour. I believe that is where the insulated issue was addressed.

There is contact with earth around the parameter of the pour on the sides.

The last job I did in this juristiction was 4 years ago and the inspector asked me why I installed a bonding bushing on a 2-1/2" rigid feed entering a concentric knock out in a meter can.

Most inspectors I deal with are very helpful and have no problem explaining them selves and can back up there interpritation.

I still think I should bring this issue up to the lead inspectors.

Mike
 
Palmbay said:
Great replys, Thank you.



The last job I did in this juristiction was 4 years ago and the inspector asked me why I installed a bonding bushing on a 2-1/2" rigid feed entering a concentric knock out in a meter can.



Mike
Click to expand...

I think I learned here recently that concentric ko's are now ok to be used for grounding. No grounding bushings required. It caught me by surprise, and I didn't follow up on it. I believe Roger made the post. Someone please correct me if I'm wrong. I'm gonna search for it.

John
 
j_erickson said:
I think I learned here recently that concentric ko's are now ok to be used for grounding. No grounding bushings required. It caught me by surprise, and I didn't follow up on it. I believe Roger made the post. Someone please correct me if I'm wrong. I'm gonna search for it.

John
Click to expand...


I don't see how this is code compliant on a service. If a standard locknut isn't even good enough to bond a service raceway how can a concentric KO be permitted as suitable for bonding?
 
Trevor,

I guess you right. I wasn't thinking about services in my reply. Until I read a post a few weeks ago, I didn't realize that most concentric knockouts are now rated for grounding. That's what I was trying to throw out there. Thanks,

John
 
John, I remember a thread that touched on this but I didn't post in it.

If it comes to me I'll let you know or post the link.

Roger
 
Talking about Ufer grounds. I'm getting ready to wire another log cabin on top of the mountain. The footer man has been there for over a week digging and jackhammering. This site is nothing but solid rock. The footers are 36" wide with 6 runs of #5 re-bar all the way around. It also has a center course connecting the sides for a load bearing wall. The pour will be approx 12" deep and the bottom of the footers are about 24" down. It's a heck of a foundation. I went by yesterday and made my connection for the Ufer. I was talking to the "builder" about the ground system, and he said that a "electrician" friend of his had said that he never installs a Ufer because lightning can blow holes in the footer or foundation. I explained that it is a good system, and the only system that doesn't require a supplementary electrode. Plus there is no way to get a ground rod in at this site, either driven or in a trench. I've heard tales of lightning damage to the footers, but I've never personally seen or had this problem. Lightning storms are a regular occurence around here. Anyone ever seen a Ufer (or foundation) that was damaged by lightning?
steve
 
If you got a big enough strike to blow out the footing, how much of the house do you think will be left??

Never done any research on it, but I have heard of it.

I would think it would have to be a direct hit to blow out the footing.

Does anyone know?
 
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