UFER grounding

[LarryFine]

My qs is if I can use these rebars as grounding electrode for earthing the Solar system & equipements.

I would say that the answer is yes.

 

[LarryFine]

I thank you all for such an amazing helpful discusion

Isn't it amazing how complicated a yes-or-no question can be?

 

[SAL568]

Isn't it amazing how complicated a yes-or-no question can be?

Basically I'm a Mechanical Engineer and have extensive electrical background too but these situations make me more curious about how simple yes or no qs can be challenging.

 

[GoldDigger]

I simply do not read it that way, but I can see that is what it says.

That is just very poor wording, however given the horizontal rings the tie the vertical bars together, I would expect it does have 20' of bar in the horizontal orientation. When this section was rewritten for the 2011 code, the language was changed without any technical substantiation, looking at the proposal, it was not the intent to remove the language that appeared in the 2008 code.


But the actual language does say what you say....just not going to enforce it that way around here.

There is a slight preference for interpreting the construction as "horizontally (within...... or within......)", based on grammatical parallelism, but based solely on English grammar rules the other interpretation, shown in post 34, is just as correct. When two alternative readings are both grammatically correct, there is a strong preference for the reading that makes sense.

 

[hornetd]

UFER is a slang term for CEE, concrete encased electrode.

Herbert Ufer was an electrical engineer and vice president of Underwriters Laboratories who was brought in to solve the continuous losses of munitions stored in Concrete magazine bunkers around Flagstaff Arizona during WWII. Every time a lightning storm came through the area side flashes inside the magazines would cause large quantities of ammunition destined for the Pacific theater of the war to explode. The losses of ammunition in storage was becoming a large burden on the munitions suppliers who could not replace the losses and keep up with war demand at the same time. The desert plateau around Phoenix was so dry that conventional Grounding methods were turning out to be ineffective in dealing with the lightning. Ufer devised a Grounding Electrode System which connected all of the reinforcing steel in the footer and floor of the magazine bunkers into a single electrode by having the steel workers double tie each crossing point of the reinforcing rods. Since it is in the nature of concrete to hold a steady level of water content even in a very dry environment the combination of the reinforcing steel and concrete in the entire floor and footer of the magazines was a very effective Grounding Electrode System. A concrete encased electrode is a faint imitation of the Ufer Ground that Herbert Ufer devised. A concrete encased electrode is no were near as effective as a true Ufer Ground is.

Tom Horne

 

[rlqdot]

footing depth is about 15 feet, the steel rod is 15mm and 6 of these rods are in one column.
If you could help me decide whether this could be used as a grounding conductor by measuring resistance through a multimeter?

i know that i am VERY late to this discussion, but the words "rods are in one column" really concern me. a column is typically a vertical concrete element and normally not in direct contact with the earth - isn't the concrete that surrounds a CEE required to be in direct contact with the earth (as in HORIZONTAL BARS IN A BUILDING FOOTING)??? my understanding is that the effectiveness of the CEE relies on moisture captured in the concrete improving the bond to the rebar / CEE and the relatively high compressive forces at the concrete against the earth reducing the resistance between the earth and the CEE at that interface. now, that column rebar probably does eventually tie to horizontal rebar in / at a footing, but i don't think we know the full story from this OP comment.

 

[jim dungar]

i know that i am VERY late to this discussion, but the words "rods are in one column" really concern me. a column is typically a vertical concrete element and normally not in direct contact with the earth....

In the OP, it was stated the footer part of the column is in contact with earth for 15'.

 

[rlqdot]

In the OP, it was stated the footer part of the column is in contact with earth for 15'.

depends on your reading of the OP - all it says is "footing depth is 15 feet". i agree that the implication is that the footing includes some rebar - but there is nothing that tells us what that reinforcing is or whether there is any at all. i sincerely doubt that a building with a concrete column containing 6 rebar would be built upon a non-reinforced footing, but in today's world, i hesitate to assume much. in any case, this concern is probably not the key element of discussion here. all this sounds to me like a situation where no physical connection to the footing rebar was provided and now the electrical contractor is on site and sees rebar visible in the column before the next lift of column concrete is poured and wants to connect to that rebar rather than expose footing bars.

just noticed that OP clarified in post 20 that the column is surrounded by earth ... again, this is not the precise expectation of a CEE - the vertical interface between concrete and earth does not provide the same low-electrical-resistance as a horizontal concrete-to-earth interface where the weight of the building rests on the footing.

again, probably not a huge issue, but also not in the true spirit of the NEC. the NEC does accept "normal" rebar ties for transferring the electrical energy from one bar to another, so at the end of the day, i guess any energy introduced into the column bars does eventually make its way to the footing bars if not transferred to earth at the vertical interface.

 

[jim dungar]

depends on your reading of the OP - all it says is "footing depth is 15 feet". i agree that the implication is that the footing includes some rebar - but there is nothing that tells us what that reinforcing is or whether there is any at all. i sincerely doubt that a building with a concrete column containing 6 rebar would be built upon a non-reinforced footing, but in today's world, i hesitate to assume much. in any case, this concern is probably not the key element of discussion here. all this sounds to me like a situation where no physical connection to the footing rebar was provided and now the electrical contractor is on site and sees rebar visible in the column before the next lift of column concrete is poured and wants to connect to that rebar rather than expose footing bars.

just noticed that OP clarified in post 20 that the column is surrounded by earth ... again, this is not the precise expectation of a CEE - the vertical interface between concrete and earth does not provide the same low-electrical-resistance as a horizontal concrete-to-earth interface where the weight of the building rests on the footing.

again, probably not a huge issue, but also not in the true spirit of the NEC. the NEC does accept "normal" rebar ties for transferring the electrical energy from one bar to another, so at the end of the day, i guess any energy introduced into the column bars does eventually make its way to the footing bars if not transferred to earth at the vertical interface.

The NEC absolutely allows for vertical CEE. It makes no reference to a minimum horizontal distance.
How do you know that a vertical interface does not have the "same low-electrical-resistance as a horizontal"? What resistance is required for any CEE