Concrete encased electrode. Ufer Rod

[cliffcharb]

Quick question on Ufer rod requirements. My concrete contractor is not familiar with these so looking over codes it’s seems pretty straightforward. I purchased 25’ of sleeved 4ga wire and an approved clamp to tie into the rebar.
Do I just bring the cable up in my desired location or does it need to run through pvc.
I’ll cut 20’ of sleeve off where it sits in the footers.

 

[Half-fast eddie]

Quick question on Ufer rod requirements. My concrete contractor is not familiar with these so looking over codes it’s seems pretty straightforward. I purchased 25’ of sleeved 4ga wire and an approved clamp to tie into the rebar.
Do I just bring the cable up in my desired location or does it need to run through pvc.
I’ll cut 20’ of sleeve off where it sits in the footers.

Have you checked code? I thought ufers were only allowed in certain soil conditions, where it isn’t practical to drive a ground rod.

 

[dcg9381]

Around here the electricians install the UFERs just prior to pour. I've seen some good internet on 'em. What I typically see is that the copper comes through the concrete in flex conduit... I see it labeled "non-metalic protective sleeve" in many diagrams.

 

[u2slow]

The key thing here with a ufer is placing it correctly in the footing, and having the AHJ sight it before the concrete pour. Or find out if pictures are acceptable.

 

[duneslider]

In my area the rebar in the foundation/footing is the ufer, they do not use a Wire. The UFER rebar is stubbed up through the top of the foundation and then the electrician attaches the ground from the panel to the ufer rebar with a clamp.

 

[Half-fast eddie]

I think i’m right with the following statements. If not, i hope someone will correct me. (Hah! As if anyone here would hold back.)

1. The term Ufer is not in the NEC.
2. What everyone calls an ufer ground is actually just bonding to the rebar in the foundation.
3. A code compliant ground rod is still required, in addition to the rebar bond.

 

[mm08822]

In my area the rebar in the foundation/footing is the ufer, they do not use a Wire. The UFER rebar is stubbed up through the top of the foundation and then the electrician attaches the ground from the panel to the ufer rebar with a clamp.

I like this approach much better.........copper tends to disappear, re-bar not so much.

 

[larry_g]

The key thing here with a ufer is placing it correctly in the footing, and having the AHJ sight it before the concrete pour. Or find out if pictures are acceptable.

That was my experience. The inspector had to inspect and LABEL the ufer before concrete was poured. The ufer was also bent and came up above the concrete for attaching the ground wire to.

lg
no neat sig line

 

[duneslider]

I like this approach much better.........copper tends to disappear, re-bar not so much.

I believe in my area it has to be a 20' piece of at least 1/2" and has to be tied to rebar in the foundation/footing. It is also inspected during the rebar inspection before pouring concrete.

 

[alfredeneuman]

A code compliant ground rod is still required, in addition to the rebar bond.

No additional grounding is needed for a concrete encased electrode.

 

[larry4406]

I believe in my area it has to be a 20' piece of at least 1/2" and has to be tied to rebar in the foundation/footing. It is also inspected during the rebar inspection before pouring concrete.

Most of the verbiage says "20' continuous concrete encased electrode".

As most rebar is less than 20', how does one provide 20' continuous rebar in the footing yet still turn up some distance so its accessible to connect the ground wire via an acorn nut? Continuous means unbroken or whole, so how does one comply with this? No one welds rebar in the field, at least not in production homes in my area.

In one county I build, they want rebar to overlap a minimum of 5 diameters and be wire tied so as to produce the "20' continuous". I would wager that the conductivity provided by lapping the rebars together and tying this way is no where near as conductive as a virgin unspliced 20' stick of rebar.

In another county I build, they won't accept the rebar. They demand a continuous #4 copper wire that is wire tied to the footing cage for a full 20'+ and then this wire turns up out of the footing for later connection by the electrician. If planned right, it turns up at the panel location with sufficient length that it connects to the ground bar in the panel without junction.

I do what the AHJ wants.

 

[u2slow]

Most of the verbiage says "20' continuous concrete encased electrode".

As most rebar is less than 20', how does one provide 20' continuous rebar in the footing yet still turn up some distance so its accessible to connect the ground wire via an acorn nut? Continuous means unbroken or whole, so how does one comply with this? No one welds rebar in the field, at least not in production homes in my area.

20' of bare copper in the concrete is the electrode. Attaching it to rebar is secondary. My AHJ wants to see that copper in the lower portion of the pour to help ensure moisture content. Check your rules.

 

[larry4406]

20' of bare copper in the concrete is the electrode. Attaching it to rebar is secondary. My AHJ wants to see that copper in the lower portion of the pour to help ensure moisture content. Check your rules.

Agreed.

However, many folks and jurisdictions ONLY use rebar as the UFER. They run the rebar in the footing, and bend it up thru the footing and future slab for connection by the electrician. Thus the rebar method is not 20’ continuous concrete encased and is spliced by lapping and wire tied and everyone simply looks the other way and ignores this.

The “rebar” method county I build in won’t accept the copper wire method. Go figure.

I like the copper method.

 

[Half-fast eddie]

In one county I build, they want rebar to overlap a minimum of 5 diameters

You sure about that? 5 diameters for #6 rebar is less than 4”.

 

[nadogail]

When my Electric Service Panel was upgraded to 200 Amps a few years (maybe 4) the inspector made me show him the UFER ground.

 

[u2slow]

This thread illustrates the trouble with the ufer. Concrete is usually a big push to get placed, and folks don't want to take the time to work through the particulars with the AHJ.

 

[billconner]

I put one in this past summer. First called inspector to verify what he required. 20' PC of rebar (that's all I buy) near bottom of footing. #4 bare copper wire clamped to it - make sure clamp is listed for wet location - and just run bare, taped to rebar stub (for blocks) temporarily. Inspector wanted to see it before pour. No additional ground rod. I'm sure it varies.

 

[cliffcharb]

Thanks all. Unfortunately the inspectors don't take kindly to Mr homeowner. I never received a call back. I ended up tying & clamping a 20' 4awg wire directly to the footing rebar, stubbed up through a anchor bolt holder. I made sure to leave 5' of sleeved wire available that can be hooked into the breaker box.
I have my mono slab & ufer connection inspection tomorrow. We'll see how it goes.
Got a chuckle from the comment on the form board survey, which is supposed to verify elevation & location. "Appears to be correct"

 

[larry4406]

You sure about that? 5 diameters for #6 rebar is less than 4”.

That's what the inspector said he wanted, so he got that as a minimum.

Not one inspector I have spoken with will provide clarity on how a single piece of rebar, that is 20' or less, can be 20' continuous in the footing, then turned up thru the footing and future slab (not part of the 20'), all while still being continuous, and somehow actually becoming longer than 20', to enable the acorn nut (a junction) to be accessible. Can't be done unless the bars are spliced (lapped/welded, ?)

Embedding the acorn nut (a junction) in the concrete makes it non-accessible.

We have to provide a mud ring in the drywall covered framed wall to provide access to the acorn nut junction of copper to rebar.

This is why I think the rebar method is flawed and the AHJ's just look the other way.

I prefer the copper wire method given a choice with enough extra length to run fully to the panel (no splice) and therefore no mud ring needed since the junction is inside the panel and is accessible.

@cliffcharb - take and retain detailed pictures of your copper wire ground installation with tape measure in field of view prior to your pour. I did for my barn and at final the inspector was asking where the rebar and acorn nut were and I had posted my pictures of the copper wire installation. The inspector had to call his supervisor to accept the copper wire (he was used to seeing the rebar method).

 

[billconner]

Not one inspector I have spoken with will provide clarity on how a single piece of rebar, that is 20' or less, can be 20' continuous in the footing, then turned up thru the footing and future slab (not part of the 20'), all while still being continuous, and somehow actually becoming longer than 20', to enable the acorn nut (a junction) to be accessible.

My inspector was clear and I thought code was also. 20' rebar all in footing, wet rated acorn nut, #4 brought up out of footing (and grouted block) with enough left to terminate in panel.

 

[Half-fast eddie]

That's what the inspector said he wanted, so he got that as a minimum.

Maybe you meant 50 diameters, not 5 …

 

[luvtheheat]

I had my slab poured 6 days ago. This is what Pima County (just outside Tucson city limits) requires. #6 copper clamped to rebar, then up through the pour to eventual subpanel located on inside. This specific piece of rebar was probably 12' long and tied by steel cables to all the other rebar.

No additional ground rods 6-8 feet straight down required.

Permitted and approved by the county prior to the pour.

 

[WisJim]

I built a new garage/shop starting in 2019, with floating slab, and my building inspector required "ufer" style ground, so I did an internet search for "ufer" or concrete encased ground and found lots of good explanations. The only thing not clear (as far as I could find) was whether having the slab fully insulated (2" foam insulation under and around the slab) affected the electrical grounding system. My inspector wanted the rebar bent up out of the slab and connected to the copper grounding conductor outside of the concrete, and made accessible for inspection. So my connection has a small wall panel that can be removed to see the connection. Since I was uncertain about the ufer ground when the slab is insulated, I also installed two 8 foot long grounding rods, over 6 feet from the foundation and 6 feet apart.

 

[duneslider]

I'm no electrical engineer, I just know what I see done in my area. Basements are the norm here so what is done here is a 20' rebar will be horizontal in the footing and then a second 20' is bent to allow a vertical that will stick up above the top of finished foundation. That generally leaves greater than 10' horizontal tied to the footing steel. The NEC seems to think that tying bars together with "usual steel tie wires" is enough. This is inspected at the footing rebar inspection and then again verified it is there in the foundation rebar inspection. A ground rod is still required to be installed near the panel where power enters the house and panels are tied to the ufer and the single ground rod.

NEC 250.52
(3) Concrete-Encased Electrode. A concrete-encased electrode 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 electrically 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

(2) Bare copper conductor not smaller than 4 AWG

Metallic components shall be encased by at least 50 mm (2 in.) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or within vertical foundations or structural components or members that are in direct contact with the earth. If multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

 

[Half-fast eddie]

The only thing not clear (as far as I could find) was whether having the slab fully insulated (2" foam insulation under and around the slab) affected the electrical grounding system.

Seems like the foam insulation would prevent the concrete from “bonding” with the soil.

 

[duneslider]

Seems like the foam insulation would prevent the concrete from “bonding” with the soil.

Generally the slab is not considered part of the ufer, unless it is a monolithic pour. Usually it is just the footing portion that is the ufer. But it is possible that if the inner footing is also insulated there wouldn't be enough contact. Still nothing wrong with adding a few grounding rods outside.

 

[wyliesdiesels]

I think i’m right with the following statements. If not, i hope someone will correct me. (Hah! As if anyone here would hold back.)

1. The term Ufer is not in the NEC.
2. What everyone calls an ufer ground is actually just bonding to the rebar in the foundation.
3. A code compliant ground rod is still required, in addition to the rebar bond.

Not true

If there is a UFER/CEE, code doesnt require a supplemental ground rod. UFER is all thats required

 

[WisJim]

Seems like the foam insulation would prevent the concrete from “bonding” with the soil.

That was my concern and since I couldn't find an answer to that question, I added the ground rods.

 

[Half-fast eddie]

(Delete)

 

[cliffcharb]

Well passed inspection yesterday. Inspector stated he hadn't seen anyone use wire before, but it works. Also had to cut out the vapor barrier underneath the 20' section of rebar that the wire was tied to for proper grounding. The rebar is sitting on plastic chairs, but whatever makes them happy.

 

[Half-fast eddie]

Also had to cut out the vapor barrier underneath the 20' section of rebar that the wire was tied to for proper grounding. The rebar is sitting on plastic chairs, but whatever makes them happy.

But when you cut the VB, won’t that let the concrete come in contact with the soil? It’s like the old kids song … wire connected to the rebar, rebar connected to the concrete, concrete connected to the soil.

 

[Almost Retired]

The trick to the concern of the rebar not being electrically continuous is that concrete is extremely conductive
this is the reason that GFCI protection is required in garages and unfinished basements

if the concrete is not allowed to touch the earth, then it is not grounded to the earth
however the ufer connection connects it to the panel grounding system which must also be connected to an external grounding system such as two ground rods a minimum of 6' apart but no specified distance from the slab

there are two reasons to connect all electrical systems to earth ground
1) it prevents a shock occuring because of voltage difference between the earth and say the meter can, (but not the interior if it is live)
2) it also stabilizes the voltage supplied by the utility

 

[Max]

The trick to the concern of the rebar not being electrically continuous is that concrete is extremely conductive
this is the reason that GFCI protection is required in garages and unfinished basements

if the concrete is not allowed to touch the earth, then it is not grounded to the earth
however the ufer connection connects it to the panel grounding system which must also be connected to an external grounding system such as two ground rods a minimum of 6' apart but no specified distance from the slab

there are two reasons to connect all electrical systems to earth ground
1) it prevents a shock occuring because of voltage difference between the earth and say the meter can, (but not the interior if it is live)
2) it also stabilizes the voltage supplied by the utility

Welcome to GJ. And sorry, not buying #2 at all. I'd also add 0) Provides a path to earth for things like lightning.

 

[u2slow]

Grounding is a huge topic with many facets and arguments. Code decides on a handful of methods they deem acceptable.

In Canada, we don't ground outbuildings by default, unless it will house livestock. Otherwise it's by engineer spec for specific purposes.

 

[Max]

Grounding is a huge topic with many facets and arguments. Code decides on a handful of methods they deem acceptable.

Agreed.

In Canada, we don't ground outbuildings by default, unless it will house livestock. Otherwise it's by engineer spec for specific purposes.

Ok.

My point was/is that a ground reference does nothing to stabilize the incoming voltage. We are welcome to our opinions on different aspects of grounding, but we don’t get to make up our own facts.

 

[u2slow]

@Max not challenging your content.

Grounding often becomes an embattled topic here. It's not as black and white as a particular rulebook make it out to be.

 

[Almost Retired]

Welcome to GJ. And sorry, not buying #2 at all. I'd also add 0) Provides a path to earth for things like lightning.

TY. you may not be directing those comments at me because i did not specify wire sizes,
but if by 0 you mean "one aught", that is written 1/0

the size of the ground wire required for the grounding electrode (rod, ufer, etc.) is determined by the size of the service it is connected to
as well as the NEC and the utility, around here #4 is required for a 200A service
i have installed an 800A service that required a 1/0 wire to the rod

lightning protection is provided by a separate installation if you want it added
i have seen lightning use a #6 ground wire as easily as it did the 12AWG in the house wiring

 

[Almost Retired]

Agreed.

Ok.

My point was/is that a ground reference does nothing to stabilize the incoming voltage. We are welcome to our opinions on different aspects of grounding, but we don’t get to make up our own facts.

i will respectfully differ
until something goes wrong you are correct, it does not help,
but if you lose your utility neutral connection, as well as your ground connection for your house
you will instantly have 240V on one leg, and 0V on the other (that is how the pole transformer is built)
i have seen that and verified it with a voltmeter in an existing residence
i have over 30 years electrical experience in residential, commercial, industrial, and offshore drilling rigs

 

[larry4406]

The trick to the concern of the rebar not being electrically continuous is that concrete is extremely conductive
this is the reason that GFCI protection is required in garages and unfinished basements

if the concrete is not allowed to touch the earth, then it is not grounded to the earth
however the ufer connection connects it to the panel grounding system which must also be connected to an external grounding system such as two ground rods a minimum of 6' apart but no specified distance from the slab

there are two reasons to connect all electrical systems to earth ground
1) it prevents a shock occuring because of voltage difference between the earth and say the meter can, (but not the interior if it is live)
2) it also stabilizes the voltage supplied by the utility

In our new construction homes, we have not driven external ground rods for home electrical service for at least 10-12 years once the concrete encased electrode method came on. We only have the concrete encased electrode, not in addition to two ground rods. Prior to the concrete encased electrode method, we had the two external ground rods minimum of 6' apart.

Only recent ground rods that have been driven at my residential job sites were for backup standby generators. These were connected to the transfer switch with 4-wire feed and the AHJ required one local driven ground rod at the generator connected to the ground wire of the 4-wire feed.

 

[Almost Retired]

as i mentioned elsewhere
the nec is not always the final word on what is acceptable
however the AHJ is the final word and we have to trust him to be knowledgeable of what his jurisdiction has adopted
this may include all or part of the code, in addition to local, city, county, state codes that may be adopted and allowed to add to
or omit parts of the code. As well as utility requirements who can add to whatever they choose, but not omit

when i said two rods i was replying to someone who said two rods and agreeing with them

my state is louisiana and they have a state building code in addition to the nec
they require two rods, or a ufer and one rod, but always 2 points of grounding