Questions on grounding the foundation rebar

[green.bubbly]

The inspector told my wife that I need to ground my rebar to a 10 foot ground rod using #4 copper wire. I understood everything that needed to be done except a couple of things. Do I drive the rod into the ground IN the footing or on the outside of the slab?

The way I understood it was that the rod should be sunk in the footing near my main breaker panel with enough rod sticking out above the concrete to run another ground wire to my panel.

Do this sound correct?


Thanks

 

[mrb]

that does not sound correct at all. you have to bond the rebar to the panel ground, not its own rod. look up ufer ground

 

[Falcon67]

Ya - I didn't get ufer grounds until I read up. Basically, the deal is that concrete is very conductive and tying into the rebar basically lets the whole slab become the "ground".

http://www.psihq.com/iread/ufergrnd.htm

Maybe is required
http://www.sonoma-county.org/prmd/docs/techbulletin/e-8x.pdf

 

[mrb]

ufer ground is required in nec 2008

 

[green.bubbly]

Sorry folks, when I saw the word ufer, I remembered that there was a recent thread on that subject.

Thanks for the info and the links.

 

[Aceman]

Just one thing I'll mention about ufer grounds that may help someone out. Here in Oregon, whoever does the rebar for the concrete, stubs a short piece of bar up for the ufer ground. The building inspector, when doing the rebar/concrete inspection then tags this stubup as suitable for a ufer ground connection. Often times this stubup gets forgotten or the building inspector forgets to tag it as suitable for a grounding electrode.

What you can do at this point, which is also perfectly acceptable, is to take at least 20 feet of #4 bare copper wire and ziptie/tie wire it to the rebar so it's embedded in the concrete by at least 2" of concrete on all sides. Just leave yourself a tail long enough out of the concrete to reach the ground buss in the panel. You do not want to have any splices in this wire. Then have the electrical inspector verify this as the ufer ground before pouring.

One example, I'm wiring a large concrete tilt-up warehouse right now where the ufer ground was forgotten for both the electrical services this building has. What I had to do was dig a trench about shovel width, the depth of the footing. Then I layed #4 copper 20+ feet long across some 2-3 inch dobies. I then had the contractor cover it with concrete. Just another idea that may save someone some trouble if the ufer is forgotten. Always run these things by your inspector first though. This was his solution for my problem.

Kinda wrote a book here....sorry guys.

 

[green.bubbly]

OK, I am trying to figure out the best or proper method of doing this. I have seen where a piece of rebar is simply bent 90 degrees and protruding up from the slab. That rebar is attached to another piece of rebar at least 20 feet long. Then the ground wire is clamped to the end of the rebar when the panel is wired.

Then as Aceman mentioned, you can just take a 20+ foot piece of #4 copper wire and attach it the the rebar in the footing and have it come out of the concrete at the panel.

Which is better or proper and do I need to encase either option in a shield where it comes out of the concrete. I kind of like the 20 plus feet of #4 copper as there is no need to worry about the rebar losing it's electrical connection. But what i do not like about just the copper wire is that it would be fairly easy to break it where it exits th concrete.

And this is why I do not sleep at night...

 

[rburke65]

I would call the electrical inspector back and ask for a clarification if you are in doubt. You don't want the hold ups if you have to re-do this again, don't need the added cost, the inspector will at least know you are trying to do this right. Lots of good answers here and lots of help, but remember, the only guy you have to make happy is the Electrical Inspector.....no one else counts.

 

[green.bubbly]

Thanks for all the input. I called John the inspector this morning and asked him what was needed. Basically all he wanted was a #4 copper wire clamped to the bottom piece of rebar. The wire then needed to come out of the bottom of the slab on the outside where it will be connected to a ground rod and the meter base.

I told him that I think I understood and then had this reply which you gotta love. He told me that it it was wrong, he would fix it for me.

Yes, I love my inspectors. They have already been so helpful and accommodating. In fact, John will be stopping by Sunday afternoon to inspect my foundation so we can start pouring concrete early Monday morning.



Below are a couple of pics...

 

[contactme_11]

That clamp to the rebar should have noalox grease between all the connections on it.

 

[Aceman]

Why is the ground wire tailed outside the building?

That clamp to the rebar should have noalox grease between all the connections on it.

I've never seen a rebar clamp Noaloxed.....

 

[mrb]

That clamp to the rebar should have noalox grease between all the connections on it.

why?

 

[mrb]

is that ground clamp listed for concrete encasement? (and is it for rebar?) it looks different than what im used to seeing. is this in canada?

 

[green.bubbly]

Why is the ground wire tailed outside the building?

From what I understand, there will also need to be a copper rod driven into the ground. That ground wire will attach to the ground rod and up to the meter base. I thought it would go inside and attach to the main panel ground bar but I had the inspector repeat what he said and he told me to run under the foundation board and lay it on the ground outside the foundation.

He was going to be around my property today to do the inspection but he called me right after lunch and said he was not coming around today so he would be there first thing in the morning to inspect. He told me if it was wrong, he would fix it for me. If it does go inside, it will be easy to do.

 

[REAL HOT SCHITT]

Run a copper ground cable (sheathed at exposed to outside end to avoid corrosion) thru forms then to a ground stake in damp corner. Note; ground works best in dampness, in dry terrain use 2 stakes @ 500 millimeter apart.

If your really cautious? U can install 2 lots of grounding at opposite corners or at each end.

 

[green.bubbly]

is that ground clamp listed for concrete encasement? (and is it for rebar?) it looks different than what im used to seeing. is this in canada?

Hmmmm?

It is for rebar and direct burial but no mention of concrete encasement.

Application: Indoors or Outdoors. Use to secure bare copper ground wire to 3/8" rebar through 1" pipe. Wire Size: #10-#2 AWG. Materials: Bronze with Stainless Steel Screws. Features This new JRD is extremely versatile - fits 3/8" - 1" Rebar, 1/2" - 1" pipe, 1/4" - 1" ground rods. Can be used for mechanically connecting 2 #8 sol wires. Use on water pipes or for direct burial - no need to stock two clamps. Lay-In Lug feature is a tremendous labor saver - no threading through holes - just lay-in ground wire and tighten screw.

Although the one I used seems to have bronze screws instead of SS. He did say that the screws had to be bronze as well.

He did tell me that the store right by my property had the bronze clamps and I have a section of 20' 5/8 rebar on standby if needed.


Don't make me lose sleep tonight. I already tossed and turned last night trying to think of anything I missed before the concrete goes in.

 

[Norcal]

That clamp to the rebar should have noalox grease between all the connections on it.

Unless you have manufacturers instructions stating to do so, it is not necessary.

 

[Norcal]

From what I understand, there will also need to be a copper rod driven into the ground. That ground wire will attach to the ground rod and up to the meter base. I thought it would go inside and attach to the main panel ground bar but I had the inspector repeat what he said and he told me to run under the foundation board and lay it on the ground outside the foundation.

He was going to be around my property today to do the inspection but he called me right after lunch and said he was not coming around today so he would be there first thing in the morning to inspect. He told me if it was wrong, he would fix it for me. If it does go inside, it will be easy to do.

If you have a concrete incased electrode (Ufer) you do NOT need a ground rod. If you have a metallic underground water pipe, that must be used as a grounding electrode, & the Ufer will become the required supplemental electrode...

 

[acer66]

Since we are on the topic I have a question about ufer ground,
because I am in the process of fixing up a barn.
The existing foundation is a single for doors interrupted row of cinder blocks
and the electric is not working and is going to be removed/replaced.
The plan is the remove the cider blocks and replace it with concrete and 2 rows of cider blocks
which is also going to be interrupted by openings for 2 doors, dividing the foundation into two parts.
I do not plan to use re-bars but maybe put one in for ground if that is up to code.
There will be no slap, besides maybe in one of the rooms and I am under NEC2008 ruling
and the plan is to add a small sup panel for like 40~60amp.
Water pipe is going to be pex if that matters.

Thank you

 

[green.bubbly]

Alright, inspector John just left and the foundation and UFER ground is good to go. He did say that we will need to attach that #4 ground wire from the rebar to a ground rod at the service entrance. Sounds like double grounding but I guess it is better than a poor ground. Plus, I am not going to argue with the inspector.

 

[Norcal]

Alright, inspector John just left and the foundation and UFER ground is good to go. He did say that we will need to attach that #4 ground wire from the rebar to a ground rod at the service entrance. Sounds like double grounding but I guess it is better than a poor ground. Plus, I am not going to argue with the inspector.

Your inspector is a idiot/incompetent, there is NO code section requiring a rod when a concrete incased electrode is used.

 

[Gooch]

Your inspector is a idiot/incompetent, there is NO code section requiring a rod when a concrete incased electrode is used.

While the NEC does not require it, some POCO's do. But there is no need to take this to a ground rod, it can go to the panel and land on the ground/neutral bus there.

 

[Aceman]

Your inspector is a idiot/incompetent, there is NO code section requiring a rod when a concrete incased electrode is used.

To go along with what Norcal said, since you're only going to be doing this once, I'd drive the rod and move on. I do this for a living, so I'd absolutely ask him for a code reference requiring this before I did it(possibly a local amendment to the NEC for this, but not likely!).

 

[green.bubbly]

It seems that a ground rod would be redundant but I have too good of a relationship with my inspectors to ask them to cite codes over a $15.00 ground rod.

 

[Norcal]

While the NEC does not require it, some POCO's do. But there is no need to take this to a ground rod, it can go to the panel and land on the ground/neutral bus there.

I agree that some PoCo's do require a rod (North Arkansas Electric Cooperative will not accept a Ufer, it must be a driven ground rod) a construction inspector is not a PoCo inspector. Now if the inspector had said the PoCo will require a ground rod, that I would buy, & thank him for the info.

 

[gnxtc2]

Do NOT drive another ground rod. I repeat - Do NOT drive another ground rod.

Not a fan of the type of clamp you used, but it's approved. Go to the electrical supply house and pick yourself up a Greeves clamp, aka: Jones Bond.

I do this for a living. The wire in the pic is not #4, looks like #10 or #8 solid. The wire has to run from the rebar to the main panel unbroken.

If you cannot get this accomplished before the pour, have the mason attach a piece of rebar to the rebar frame and have it stick out of the form. You can attach to it later.

Your inspector is an idiot.

Billy T.
[email protected]

 

[gnxtc2]

While the NEC does not require it, some POCO's do. But there is no need to take this to a ground rod, it can go to the panel and land on the ground/neutral bus there.

It has to go back to the main panel.

Billy T.
[email protected]

 

[mrb]

It has to go back to the main panel.

Billy T.
[email protected]

huh? the GEC would go to the ground bar in the subpanel at the detached structure, and the EGC would go from there back to the main panel

 

[gnxtc2]

huh? the GEC would go to the ground bar in the subpanel at the detached structure, and the EGC would go from there back to the main panel

It all depends on the detached structure. If the GEC goes back to the subpanel at the detached structure then the sub panel will have to become a main panel for the detached structure. The EGC that goes to the sub panel will have to come off and the neutral bonded. Then a ground rod(s) must be driven as a supplemental to the GE.

Example: If the GEC goes to the sub panel in the detached structure and the resistance to ground is less at the detached structure, the EGC becomes the GEC. Usually the EGC feeding the sub panel is much smaller in size than the GEC and will burn up if there is a fault.

or

If the main panel looses the GEC then the EGC going out to the sub panel becomes the GEC. Which we're back to same situation with it being smaller than the GEC.

Billy T.
[email protected]

 

[mrb]

It all depends on the detached structure. If the GEC goes back to the subpanel at the detached structure then the sub panel will have to become a main panel for the detached structure. The EGC that goes to the sub panel will have to come off and the neutral bonded. Then a ground rod(s) must be driven as a supplemental to the GE.

Example: If the GEC goes to the sub panel in the detached structure and the resistance to ground is less at the detached structure, the EGC becomes the GEC. Usually the EGC feeding the sub panel is much smaller in size than the GEC and will burn up if there is a fault.

or

If the main panel looses the GEC then the EGC going out to the sub panel becomes the GEC. Which we're back to same situation with it being smaller than the GEC.

Billy T.
[email protected]

what? detached structure needs 4 wires from the main at the house (as of 2008). cant bond N+G at the detached structure. detached structure needs a grounding electrode (ufer, or pair of ground rods if no cee exists, or...) grounding electrodes and the GEC dont have anything to do with clearing a fault..

read this http://ecmweb.com/grounding/electric_grounding_vs_bonding_2/

 

[green.bubbly]

Do NOT drive another ground rod. I repeat - Do NOT drive another ground rod.

Not a fan of the type of clamp you used, but it's approved. Go to the electrical supply house and pick yourself up a Greeves clamp, aka: Jones Bond.


I do this for a living. The wire in the pic is not #4, looks like #10 or #8 solid. The wire has to run from the rebar to the main panel unbroken.



Your inspector is an idiot.

Billy T.
[email protected]

It is indeed #4 wire. It is attached to 5/8" rebar and not 1/2" which may explain why it looks smaller.

I understand that the copper wire must go to the panel unbroken but educate please me on what harm having it attach to a ground rod as well. Of course I am far from an electrician but I do not see what the issue of having a ground rod in addition to the UFER. In my mind, if for some reason the ground wire to the rebar ever loses continuity, you would have the ground rod still functioning as a ground.

 

[mrb]

It is indeed #4 wire. It is attached to 5/8" rebar and not 1/2" which may explain why it looks smaller.

I understand that the copper wire must go to the panel unbroken but educate please me on what harm having it attach to a ground rod as well. Of course I am far from an electrician but I do not see what the issue of having a ground rod in addition to the UFER. In my mind, if for some reason the ground wire to the rebar ever loses continuity, you would have the ground rod still functioning as a ground.

are you in canada?

here in the usa, ufer is all you need -if you dont have it then two ground rods 6ft apart are required. if a water pipe is present you have to bond it.

 

[MrMark]

what a mess. Has there ever been a more misunderstood subject then bonding and grounds.

 

[MrMark]

It is indeed #4 wire. It is attached to 5/8" rebar and not 1/2" which may explain why it looks smaller.

I understand that the copper wire must go to the panel unbroken but educate please me on what harm having it attach to a ground rod as well. Of course I am far from an electrician but I do not see what the issue of having a ground rod in addition to the UFER. In my mind, if for some reason the ground wire to the rebar ever loses continuity, you would have the ground rod still functioning as a ground.

There is no harm, it's just stupid and makes for a messy install. The ground rod or UFER doesn't do what you think anyway, so I wouldn't lose any sleep over it.

 

[MrMark]

It all depends on the detached structure. If the GEC goes back to the subpanel at the detached structure then the sub panel will have to become a main panel for the detached structure. The EGC that goes to the sub panel will have to come off and the neutral bonded. Then a ground rod(s) must be driven as a supplemental to the GE.

Example: If the GEC goes to the sub panel in the detached structure and the resistance to ground is less at the detached structure, the EGC becomes the GEC. Usually the EGC feeding the sub panel is much smaller in size than the GEC and will burn up if there is a fault.

or

If the main panel looses the GEC then the EGC going out to the sub panel becomes the GEC. Which we're back to same situation with it being smaller than the GEC.

Billy T.
[email protected]

wow@

 

[gnxtc2]

Has there ever been a more misunderstood subject then bonding and grounds.

Yes, women

Billy T.
[email protected]

 

[green.bubbly]

There is no harm, it's just stupid and makes for a messy install. The ground rod or UFER doesn't do what you think anyway, so I wouldn't lose any sleep over it.

That is what I wanted to hear.