Mike, Very interesting but from the date on the article why 36 years later.? Don

I have to wonder if the same effective earth ground can be obtained by encasing a #4 AWG conductor or a 20' piece of 1/2" rebar in the concrete slab of a basement. Why does the UFER ground need to be in the footing? What about burying a 20' piece of rebar 12" in the dirt, then pouring concrete over it? Would that not provide an effective ground?

I want to take the time to thank you for all your update code email, and would like to become an administrator plus I need to renew my 3 yrs. classes, have not done any yet, can you give me proper direction. My contact number is (206) 679-0589--Thank You very much -- my low volt license in wa. expires july 31 06 you can also reach me at Mike@secondeditionconsulting.com www.secondeditionconsulting.com

I have to say that, like Don, I was kind of confused when I saw 1970 after opening the document....

Was this email meant to stir the discussion to get it going again?

But like Mike Sapiens said - THANKS for all the GREAAAAAAT info and services you provide us! ~(:- )

Before I trust concrete to be a ground of low enough impedance. I think that studies of fresh versus a logarithmic drying concrete impedence study to be done before using it.

The best one I saw was in the old Denver Gas and Light building in Denver. The place is now CBD the center for all fiber loops in the Dever area.

In the basement is a 30 foot pipe going straight down with a copper ground rod in it. The pipe is filled with salt. It has a water drip system that drops one drop every hour on to the salt. Every 5 years more salt is added. There is less than one ohm between earth and the copper rod as the salt is spread out into the earth and stays moist. All 10 stories of electrical and Telecom is hooked to that copper rod.

1st, its a 35-year-old document. Hardley earth shattering news.

2nd, though they discuss corrosion in the footnotes at the end, I didn't see any specific recommendation for leaving the actual ground point accessible for replacement. My experience with grounding connections has to do mostly with the galvanic deterioration of the grounding rod at the point of contact with the system.

If contractors are only just now considering use of this, there should be a convention for using a threaded or otherwise replacable connection at the system-to-ground point. (I happen to live in Florida, where they pointed out the high resistance in earth-ground.)

For some reason I can't print sheets 8 thru 12. Can you help ?

Having witnessed a lightning strike and the results of the amazingly high current flowing in the earth I am a skeptical about relying on a concrete encased electrode for lightning protection. The high current flow generates so much heat that normal materials are vaporized. I saw an (illegally) buried 14/3 extension cord dig a 12"deep trench over forty feet in hard packed soil due to the current flowing in the ground fifty feet from a lightning strike. I am skeptical that the rebar wire ties will support the sort of current generated by a lightning strike. The limited contact between crossed rebar does not inspire confidence as well. I can imagine a scenario where the rapid vaporization of moisture in the concrete could rupture the concrete and weaken an otherwise solid foundation. To qualify the use of a UFER based on the low resistance characteristics is a mistake if it cannot support the current generated by a lightning strike. Since the UFER is unexposed, it is not subject to testing or inspection after a lightning strike in order to verify its integrity. I think it is wise to rely on made electrodes of simple, reliable construction and known current capability that are easily inspected (at least by a few minutes work with a shovel). We should not focus on one, easily measured characteristic of the ground system to the exclusion of others.

Cheers,

Your March 22nd. Topic-Grounding & Bonding raised an interesting question with me. Where does the word Ufer come from? I looked in my 1970 copy of the American Electricians Handbook and the 1999 version of the NEC and I can find no reference to the word Ufer. Can you explain the origination of the Ufer grounding system?

Ufer's findings Circa. 1964 were recognized by the IEEE in the 1970 paper you referenced. Too bad it took the industry so long to welcome the relief.

This comes as no great surprise. Contractors have been using UFER's since I remember as far back as 1972 on tract in California.

Ufer was the name of the radio(?) engineer who first came up with this solution around WWII. Tall radio towers built on high mountain points with rocky soild conditions seem to benefit rom this method as far as LIGHTNING protection concerned.

To utilize the same method for electrical grounding raises several problems.

In grounding systems there are always current flows present that are equalizing current flows between different potential due to several different reasons. This unpredictable current flow and the varying moisture content of the concrete, combined with the alkaline characteristics of the concrete will rpoduce galvanic interaction between the copper wire and steel rebar, eg. corrosion, in the structural rebars AND the grounding system itself. The performance and deterioration is unpredictable. The deterioration of the structural integrity can not be remedied.

Due to concern about corrosion civil engineers sometimes specify epoxy coated rebars. In that case the rebars would be ineffective as a grounding media.

The NEC suggest that when rebars are utilized as grounding that they should be "bonded together by the usual steel tie wires or other effective means". Again corrosion will have deterious effect on thse connections and bonding it together by other means is probably not a cost effective method.

Lighting strikes had already demonstrated their destructive effect by striking the reinforcment and had blown concrete apart as predicted by another comment. That happened without intentionally trying to direct the lightning strike through the rebar.

Unfortunately the NEC is in great error in not addressing cathodic interaction of dissimilar metals in grounding system and discloses it's fundamental defficiency in establishing rules without sound engineering and scientific background and backup. But that is a whole other discussion.....

In short, fawgedeboutit.......

There seems to be something wrong with the printable version. I can only get 8 of 12 pages before I get a corruption message. Could you see what's up?

Thanks!

The article on " The use of concrete-enclosed reinforcing rods as grounding electrodes" My questions is have any new studies been done on this subject ? the article is dated 1970. Thanks...

Mike the AHJ is trying to force concrete encase grounding for dwelling in our area . my position is it's up to the building contractor to install the rebar not the electrical contractor , NEC states if it is present electrrical contractor has to connet to it. I did a testing of the ground rod connected to 20 amp CB nothing happen and connected light buob in series , bulb work fine no tripping of CB, I connect ground rod to concrete encase ground and CB trip quickly John Hall Electrical Inspector Dayton OHio.

Can You Simplify This Article?

This article is from 1970--not exactly new. Why is this now being sent out? Also, the information from Ufer is older than that. What am I missing here? I'm replying later after this e-mail went out, but I've been out of town, so this question may already have been answered.

This is important info for my business, as we put in automation systems into existing plants, and always have issues with grounding. This could be a big help to us, but I need to make sure I understand whend and if we could use this.

Any help is greatly appreciated!!

Very good site.