# New Code Change



## TimNJ (Sep 7, 2005)

I wanted to run this by some other electricians. I just poured footings for an addition today and before we poured my electrician told me about a new code change where you run your ground to your rebar. He told me it didn't have to be sleeved, just clamp the wire to the rebar and pour. This seems odd to me since copper and concrete don't have a very friendly relationship (anybody who has been around Levitt houses with copper radiant heat know what I am talking about.


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## mdshunk (Mar 13, 2005)

This is very true. This is called a "Ufer ground", named after George Ufer. Is is a very, very effective earthing path. Even better than ground rods. The code calls this a "concrete encased electrode".

The trouble with you (the footer guy) connecting the copper wire to the rebar is twofold. One, you don't always know what size service the house is getting, and therefore don't know what gauge of copper to use. Also, you may not use the correct fitting to connect the copper to the rebar, and aren't necessarily qualified to make this connection. This connection also escapes the electrical inspection. 

Because of this, most guys are bending up a piece of rebar that will stick up through the basement floor either inside a partition, or right under the panel next to the foundation wall. The upturned rebar can be anywhere at all, because you can run the copper wire anywhere. This allows you to turn up the rebar in the least objectionable place possible. If it's a crawl space, you can leave it stick up whereever it pleases you. You only need 6" to 12" sticking up above the floor, and it would be nice if it didn't have concrete slopped all over it. This way, the electrician can make the connection to the rebar, and the connection can be inspected. Plus, many inspectors require this connection to be accessable (although the code doesn't seem to mandate that), and a concrete encased connection between the copper and the rebar is not exactly accessable. 

The Ufer ground connection or the upturned rebar should be checked for during the footer inspection. If, by chance, it gets missed... it will get ugly during the electrical inspection. Exactly how ugly depends on how big of pricks the local inspectors are.

If you footer otherwise doesn't need or require rebar, you need at least one piece to satisfy the electrical code.


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## TimNJ (Sep 7, 2005)

I think that makes sense md to turn up the rebar and make the connection outside the pour. My electrician sized properly to the service and used the correct rebar clamp. The part that got me was to pull the wire up through the pour. He told me this was what the inspectors in this area that are inspecting for it wanted even though many still haven't started inspecting for it yet. He told me just as you did, it better be there because if they question it later it's a heck of a mess to try to do it after the fact.


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## mdshunk (Mar 13, 2005)

TimNJ said:


> My electrician sized properly to the service and used the correct rebar clamp.


That's good. I thought for a minute there that he wanted you to do that. 

Next time, you can just bend up a rebar tail somewhere.


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## Teetorbilt (Feb 12, 2004)

This is outside my baliwick, but I do understand basic electrics.

Where does the ground occur between the slab and ground? Here, it would have to travel through a few ins. of concrete which could be wet or dry depending on weather conditions. 

Here, our primary concern is salt intrusion. Rusting rebar can explode footers and slabs. Unless the slab is wet, I do not see the ground path in this system. We also deal with electrolosis as salt and water provide the electrolyte to varyiing degrees.

BTW, I know that I'm wrong. Just want to know why.


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## mdshunk (Mar 13, 2005)

This might go towards answering your question:
http://www.mikeholt.com/documents/grounding/pdf/ufer.pdf

Let me know if you want more, I have a good article on concrete encased electrodes on my hard drive somewhere I can dig up.


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## mdshunk (Mar 13, 2005)

"During World War II, a retired Vice President of Underwriters Laboratories, Herbert G. Ufer, developed it for the U.S. Army. Igloo shaped bomb storage vaults were being built, and possible static and lightning induced detonation problems were of concern. Ground conductivity was poor, and to be effective enough, ground rods would have to be driven several hundred feet. After much research and testing Mr. Ufer advised the Army to make connection to the steel bar that would internally reinforce the concrete foundation. He had determined that concrete was more conductive than all but the best soil, and that this improved semiconducting characteristic would enhance surface area contact with the surrounding soil. The wire ties normally used would be extra secure, and attention would be given to bonding or welding the lattice- type network together. The Army adopted the idea, and built the vaults as specified. After construction ground resistance tests were made. No measurement exceeded five ohms. This value was considered extremely low for the local soil conductivity. Later tests confirmed stability. Mr. Ufer went on to develop the concept of concrete encased grounding electrodes. Many of his findings are detailed in IEEE Transactions paper # 63-1505. His system has since been used by the military, utility companies, Lake Tahoe lifts, and industry throughout the country."


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## Teetorbilt (Feb 12, 2004)

md, It says that concrete is a 'fair grounding' and is addressing radio tower grounds which are on different freqs. and have higher potentials. Most RF towers are required to have fences around their ground radials.

Where are you going and what does this have to do with slab grounding? IMHO Rusty tiewires offer minimal contact electrically and who knows what happens as the slab is poured and booted dudes are stumbling over the grid?

Dad was glossin'. We welded everything, it was more effiicient in his book. If you think about it, it's same speed if not faster.


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## mdshunk (Mar 13, 2005)

Teetorbilt said:


> IMHO Rusty tiewires offer minimal contact electrically and


That would be true. That's why the code only required one piece of rebar or 20' of copper wire if you don't use rebar in the footer. 

The tower article probably wasn't the best one to use. They drive tower ground rods up to 100 feet or more sometimes. Dwelling ground rods are only 8', and the Ufer ground is superior to the typical ground rod we use for services. So good is a Ufer ground, that the government uses that method to ground ammo storage areas. Mind you, they pay extra attention to see that ALL the rebar is well interconnected (welded), and not just a 20' piece as required in the electrical code. 

If you think that the requirement is silly, you can have it changed. Anyone at all can write a code change proposal, and it will be looked over by NEC Code Making Panel #2 (the one that covers Ufer grounding). If indeed you are right, the Ufer grounding requirement will be dropped. Write it up and submit it. I'm not the engineer here, you are. I just follow the rules, like a mindless droan.


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## mdshunk (Mar 13, 2005)

Teetorbilt said:


> md, It says that concrete is a 'fair grounding' and is addressing radio tower grounds which are on different freqs. and have higher potentials.


Are you aware of the purpose that a Ufer ground or ground rod serves, be it a radio tower or a dwelling? It only provides a low(er) impedance path to the earth in the event of a lightning strike. Nothing more, nothing less. The frequency of equipment operating on the tower or within the home has no bearing on it.


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## Mike Finley (Apr 28, 2004)

mdshunk said:


> "During World War II, a retired Vice President of Underwriters Laboratories, Herbert G. Ufer, developed it for the U.S. Army. Igloo shaped bomb storage vaults were being built, and possible static and lightning induced detonation problems were of concern. Ground conductivity was poor, and to be effective enough, ground rods would have to be driven several hundred feet. After much research and testing Mr. Ufer advised the Army to make connection to the steel bar that would internally reinforce the concrete foundation. He had determined that concrete was more conductive than all but the best soil, and that this improved semiconducting characteristic would enhance surface area contact with the surrounding soil. The wire ties normally used would be extra secure, and attention would be given to bonding or welding the lattice- type network together. The Army adopted the idea, and built the vaults as specified. After construction ground resistance tests were made. No measurement exceeded five ohms. This value was considered extremely low for the local soil conductivity. Later tests confirmed stability. Mr. Ufer went on to develop the concept of concrete encased grounding electrodes. Many of his findings are detailed in IEEE Transactions paper # 63-1505. His system has since been used by the military, utility companies, Lake Tahoe lifts, and industry throughout the country."


That is freaken cool! There are people who actually think progressively in construction!:thumbup: 

So in regard to the real world, is this new approach cheaper, more expensive or the same to each of the parties the GC, the foundation guy, the electrician, the homeowner?


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## Bkessler (Oct 8, 2005)

It is also nice to have a good ground if for some reason you lose your nuetral.


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