Ufer connections

[Open Neutral]

So we'll have a large array of rebar, and a provided connection to same.

But I've always wondered.

1. How is the connection you get tied to the rebar in the pour?
2. Seldom is the rebar welded together; usually it's just tied. (One exception I know about is a wall for a classified [not NEC, but USG Top Secret/SCIF etc] vault location. There it's 6" spacing, ISTM.)
   

In both cases my thinking is "the only good over time connection is a soldered/{cad}welded one..." perhaps because I grew up in the salt belt & saw too many rotted ones... especially bimetallic ones.

But I've never seen a discussion of same.

 

[George Stolz]

I always thought the tie wire was a temporary measure until the concrete was poured, and then the concrete took over.

 

[John120/240]

The rebar where you make your connection is tie wired in multiple places to other rebar.

20 ft of 1/2 rebar encased in 2" of concrete located at or near the bottom of the foundation or

footing. A #4 copper is required to make the ufer connection. The 20 ft of rebar is all that is

required, contact with adjacent rebar is that much better.

 

[Open Neutral]

The rebar where you make your connection is tie wired in multiple places to other rebar.

But I doubt the tie-wire connections maintain low resistance joints over time.

A #4 copper is required to make the ufer connection.

The 20 ft of rebar is all that is required, contact with adjacent rebar is that much better.

OK, that I can grasp; but I still wonder about bonding the #4 to the rebar. My choice would be a cadweld but.....

 

[John120/240]

Yes cad weld would be permanent,they do make a listed clamp for #4 copper to 1/2 rebar.

Very similar to your waterline clamp.

 

[Open Neutral]

Yes cad weld would be permanent,they do make a listed clamp for #4 copper to 1/2 rebar.

Very similar to your waterline clamp.

Cadweld would surely fail on the 2 inch HDPE from the storage tanks....:happysad:

I was disappointed to learn that nowadaze, well casings are plastic. I'd assumed a steel wall casing would be a good addition to any ground grid...

 

[Dennis Alwon]

Here is what I do. I install 20 feet of #4 in the footer and then tie to the rebar with an acorn clamp. If the acorn or rebar is not a good connection the 20' of #4 will do the trick. BTW, I seriously doubt that once the concrete is poured that contact with the other rebar is an issue.

 

[iwire]

So we'll have a large array of rebar, and a provided connection to same.

But I've always wondered.

1. How is the connection you get tied to the rebar in the pour?
2. Seldom is the rebar welded together; usually it's just tied. (One exception I know about is a wall for a classified [not NEC, but USG Top Secret/SCIF etc] vault location. There it's 6" spacing, ISTM.)
   

In both cases my thinking is "the only good over time connection is a soldered/{cad}welded one..." perhaps because I grew up in the salt belt & saw too many rotted ones... especially bimetallic ones.

But I've never seen a discussion of same.

The tie wires are enough

250.52(A)(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of 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, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. Where mul-tiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

 

[kwired]

The tie wires are enough

My guess is his real question is "why are the tie wires enough?"

That is understandable question. If you were depending on these rebar as a current carrying conductor for some reason those tie wire connections would be considered poor connections.

I'm not sure I have the answer so I will not attempt to answer, put my foot in my mouth enough times the last few days.

 

[iwire]

My guess is his real question is "why are the tie wires enough?"

I will stick with the question asked and not guess.

I'm not sure I have the answer so I will not attempt to answer, put my foot in my mouth enough times the last few days.

It happens to all of us, often from guessing.

 

[George Stolz]

I ventured a guess above.

I always thought the tie wire was a temporary measure until the concrete was poured, and then the concrete took over.

 

[kwired]

One thing that you need to remember is grounding electrodes are not intended to carry sustained currents like a circuit conductor is. Their whole purpose is different.

 

[Besoeker]

Ignorant Brit - again.
Ufer?

 

[kwired]

Ignorant Brit - again.
Ufer?

Concrete encased electrode. Man with the last name Ufer was first to use one - or something like that.

 

[Besoeker]

Concrete encased electrode. Man with the last name Ufer was first to use one - or something like that.

Appreciated, thank you.

 

[Dennis Alwon]

Herbert Ufer did testing of a CEE in Az.

 

[copper chopper]

http://www.erico.com/public/library/fep/LT1078.pdf try this one

 

[Besoeker]

http://www.erico.com/public/library/fep/LT1078.pdf try this one

You have provided concrete evidence to reinforce previous connections with this subject........

OK. I'll get me coat.....

 

[Open Neutral]

Yes, my question is better stated "Why are tie wires between rebar good enough, given that such connections can and do corrode?" I know the lime/cement environment in theory deters that, but I'm dubious. [I'd rather we welded the rebar but the $$$$.]

And also the same concern on the connection TO the bar. On an outbuilding, the pad is already poured. What the contractor did was leave us something less than #4 wire emerging from the pour. From the pictures I've seen since; I assume we should get an actual rod length emerging; and connect above the pour. (It won't matter than much, I think; a major change has turned that outbuilding from the service entrance to instead just having a few lights and outlets. We can also pound in ground rods.)

From what I've learned, I'll ensure a long-enough rebar shall poke out at the new service entrance.

But here's a related query. The telecom entrance will be in server room; on the other side of the house. I'll need grounding there. I can get a rebar emerging there too, but think I should provide a bare wire in the pour between the two locations.



As for Ufer; during WWII, the Army needed grounding for ammunition bunkers at Fort Wingate in the southwest US. The soil was sand & rock, the water table non-existent; and Herbert Ufer's scheme saved the day.

 

[BJ Conner]

Listed Clamp

Listed Clamp

Erico makes a listed clamp.
IF your curious and working where there are rebar dowels sticking out of a slab measure the resistance between two of them. USually better than two ground rods in dirt.
http://www.erico.com/public/library/fep/LT1078.pdf