• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Concrete Encased Electrode - Ufer Ground

N

NMCB13

Member
Joined
Jun 27, 2013
Messages
13
Location
Florida
First off the State of Florida (and a few other States) are a self insured municipality. As such the State Legislators must pass timely manner (yea...OK) amendments to update to the current codes. In Florida we are working from the 2008 National Electrical Code (NEC). With that being said lets talk about the Concrete Encased Electrode (CEE). In the 2008 NEC Article 250.52(A)3 identifies the requirement for a CEE. In the current edition of the 2011 NEC article 250.52.(A)3 has a revision included which is entitled "Informational Note". This informational not states " Concrete installed with insulation, vapor barrier, films or similar items separating the concrete from the earth is not considered to be in direct contact with the earth". Another resource would be the green book, IEE Standard for grounding. If you look at IEE section 4.2.3. it will describe the CEE in depth. SO here we have a conflict in that as the Legislators drag their feet to amend the State building codes we must settle for second best. Yet, the Electrical Contractors are installing Arc fault circuit breakers and tamper proof devices, which I do not think they were required in the 2008 codes, go figure? Anyway, a true CEE need to be less that 25 ohms to be effective. In the 2011 NEC with the revision to NEC article 250.52.(A)3 they are looking for greater surface area to be in direct contact with the earth. As it stands now nobody can tell me that with the vapor barrier installed what the resistance to earth is. According to the NEC it must be less that 25 ohms. To test the CEE you need a Ground Resistance Tester and a megger or ohm meter will not work. I am having a home built and I know for sure that the vapor barrier is under the footer. The County and local inspector said that is Ok for they are enforcing the 2008 National Electrical Code......, but the electrical contractor is installing the electrical system with the 2011 NEC....Conflict? .........CAN DO..........
 
You are under the 2008 NEC. The sidewall of the footer from the monolithic pour will be in direct contact with the soil. Maybe part of the footer is separated from soil by a vapor barrier but the sides are not. Nothing says that the bottom of the footer must be in direct contact with the soil so if the sidewall of the foundation is within direct contact, that should suffice. Don't forget that there should be a lot of rebar in the CMU that is connected to the rebar in the footings. There is a lot of that slab on grade in direct contact with the soil. I would not worry about it.

If you are still unhappy and don't want to buy a meter. Throw 2 ground rods in and call it a day.
 
Wasn't the Ufer designed to ground into dry climates where regular soil did not ground effectivly? Something like more available ions in concrete for a good ground?

Brent.
 
You are apparently the owner so you get the final say on what is done if it does not comply with the code. You may have to have a discussion with the contractor about cost but you get the final vote.

The code change is warranted. It is a judgment call whether the side of the footer in contact with the soil is enough. It might be.

I do not see where it should be so difficult to check the ground resistance.

The way I read the NEC it states that the resistance shall be less than 25 ohms.
 
MASSDRIVER said:
Wasn't the Ufer designed to ground into dry climates where regular soil did not ground effectivly? Something like more available ions in concrete for a good ground?Brent.
Click to expand...
You can read up on the idea for the first Ufer Ground just google it.

I also think if the ufer ground is tied to the footing rebar it will be the way it was designed to work.
 
The way politics works in each State is beyond me, the difference with the 2008 vs. the 2011 NEC article 250.52.(A)3 is the informational note.. The 2011 NEC understands that the more surface in direct contact with the earth reduces the resistance to earth for a better ground path. And yes, 25 ohms or less is required by the NEC.
 
NMCB13 said:
Yet, the Electrical Contractors are installing Arc fault circuit breakers and tamper proof devices, which I do not think they were required in the 2008 codes, go figure?
Click to expand...
See 2008 NEC 210.12 and 406.12
 
First, welcome to the forum,

Unfortunately, many are installing vapor barriers "in the footing" and they are not suppose to put vapor barriers in the footing. 2006 & 2009 IRC, R506.2.3. Vapor retarder. A 6 mil. polyethylene or approved vapor retarder with joints lapped not less than 6 inches shall be placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists.

It does not state that the vapor retarder is to be anywhere within the footing. So, if there is vapor retarder anywhere in the footing it is not installed per code.

So, I think your problem is not with the concrete encased electrode requirements in the NEC, it is with the faulty intsallation of the vapor retarder.

Hope this helps,

Uncle Bob
 
Requiring something in one situation does not mean that it cannot be done in other situations. Suggested that a membrane under the footings was not deemed necessary but aside from the grounding issue it does not necessarily cause problems.

I am aware of a project built on an old industrial site where a membrane was sprayed on the ground under slabs and footings to control potential vapors.
 
As I read the NEC, if a Ufer ground is installed, nothing else is required. As Mike Holt taught us a few years ago, the Ground system is to take stray voltage to ground.. everything else is bonding. We've inspected some REALLY involved grounding systems (#11 steel triads with 4/0 copper).. which are really doing.. maybe nothing.

We require that the Ufer ground be installed, too.. why it can't be in the foundation walls, rather than the footing still kind of escapes me especially with additions.

As I read the Code, if a Ufer ground is installed, no ground rods are required.. please correct me if I'm wrong.
 
If you have a really, really, really good grounding electrode system that makes its way back to the POCO transformer, you will never notice when you lose a neutral. Unless of course you have a very large system that needs a very large neutral. (barring any harmonics issues that is)
 
Potential harmonics may have been the issue with the ground triad (which is where we had to take cad weld training.. I love that beer bottle opener, by the way).. but even with a Ufer, only a #4 is required.
 
If a ufer ground is installed you need no ground steaks are required.

For those that insist on a ufer ground then I assume that you will not allow a membrane to wrap the foundation. This can happen with vapor barriers but also where waterproofing is required.

Arguably walls could provide the ground contact if there were no membranes which is not likely . I would expect drainage rock not to perform as well as soil.

If you connect the ground wire to reinforcing steel and there is a ground current then it would appear that this could result in corrosion of the reinforcing steel. In addition if the ground has to take current from a lightening strike it is likely that the current could cause the concrete through which the ground flows to fracture because the high current will cause the moisture in the concrete to vaporize. I am not convinced that this will create a major safety issue for most houses still this is an unresolved question.
 
The NEC is pretty specific about the Ufer ground.. if you're placing footings, it's required.

After listening to Mike Holt for 8 hours talking about grounding vs. bonding, it seems bonding is more important to reduce the possibility of metal parts becoming energized (true.. I zoned out after about 6 hours, but I still have the book). I think the IAEI needs to change "equipment grounding conductor" to "equipment bonding conductor", because that's really what it does. The EGC needs to be properly sized; the GEC (ground electrode conductor) in no case needs to be bigger than #4 (as he explained and as I read the code). The two serve different functions. Chris Kennedy, feel free to jump in here.
 
I sat in one of Mikes grounding and bonding classes, about the time he was saying that grounding wasn't necessarily the issue, as much as bonding.............disregard some parts of the book we just handed out.

At the end of the two days, I could see where he was going.
 
Here is something I noticed when I first started inspecting in Oklahoma. Where a ufer was installed; it was done by the foundation contractor. Some builders asked me that as long as it was correct what was the problem? Why should the electrical contractor have to make a trip "just to install a bent rebar" as long as the installation is correct? The installations were installed per code. What do you do and what do you think? They ain't licensed electricians. Uncle Bob
 
peach said:
The NEC is pretty specific about the Ufer ground.. if you're placing footings, it's required.
Click to expand...
Not necessarily. 250.50 states that All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these electrodes are present, one or more of the electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

In one and two family dwellings... plain concrete footings without longitudinal reinforcement supporting walls and isolated

plain concrete footings supporting columns or pedestals are permitted.
 
Uncle Bob said:
Here is something I noticed when I first started inspecting in Oklahoma. Where a ufer was installed; it was done by the foundation contractor. Some builders asked me that as long as it was correct what was the problem? Why should the electrical contractor have to make a trip "just to install a bent rebar" as long as the installation is correct? The installations were installed per code. What do you do and what do you think? They ain't licensed electricians. Uncle Bob
Click to expand...
I allow the footing contractor to install the UFER ground and I inspect it. Seems really extreme to make the electrical contractor come out to the site to install a piece of re-bar or even a wire and clamp.

Chris
 
Mark K said:
If you connect the ground wire to reinforcing steel and there is a ground current then it would appear that this could result in corrosion of the reinforcing steel. In addition if the ground has to take current from a lightening strike it is likely that the current could cause the concrete through which the ground flows to fracture because the high current will cause the moisture in the concrete to vaporize. I am not convinced that this will create a major safety issue for most houses still this is an unresolved question.
Click to expand...
Just the flow of current through steel reinforcing bars should not create corrosion, also in talking to CMP 5 there are no know issues with a copper wire touching the steel reinforcing bars in the foundation or footing. It has been questioned before if the copper wire should be separated from the steel re-bar.

It is possible that a direct lightning strike could conceivably damage a footing but the purpose of the grounding electrode system is NOT to protect the structure from a direct lightning strike but to dissipate lightning induced currents.

Chris
 
peach said:
The NEC is pretty specific about the Ufer ground.. if you're placing footings, it's required.After listening to Mike Holt for 8 hours talking about grounding vs. bonding, it seems bonding is more important to reduce the possibility of metal parts becoming energized (true.. I zoned out after about 6 hours, but I still have the book). I think the IAEI needs to change "equipment grounding conductor" to "equipment bonding conductor", because that's really what it does. The EGC needs to be properly sized; the GEC (ground electrode conductor) in no case needs to be bigger than #4 (as he explained and as I read the code). The two serve different functions. Chris Kennedy, feel free to jump in here.
Click to expand...
I'm not that Chris but may I jump in?

I agree that sometimes we place too much emphasis on grounding and ignore the need for proper bonding but both are important.

Also IAEI is just an educational organization, NFPA is the organization that publishes the NEC.

As far as changing the term "Equipment Grounding Conductor" to "Equipment Bonding Conductor" that change has been purposed to CMP 5 and rejected every time on the basis that the EGC does in fact perform a grounding function for the equipment that the conductor is connected to, so therefore the term is a correct term. In the 2008 NEC an Informational Note #1 was added to the definition of Grounding conductor, Equipment in Article 100 that states "It is recognized that the equipment grounding conductor also performs bonding."

Chris
 
You must log in or register to reply here.
Top