Ufer connections

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Open Neutral

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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 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.
 
John120/240 said:
The rebar where you make your connection is tie wired in multiple places to other rebar.
Click to expand...

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

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

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

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 said:
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.
Click to expand...

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...
 
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.
 
Open Neutral said:
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.
Click to expand...

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.
Click to expand...
 
iwire said:
The tie wires are enough
Click to expand...

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.
 
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.
 
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.
 
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