what is a ufer ground

[adamelectro]

definition or distinction please for the record

 

[iwire]

Re: what is a ufer ground

Not so easy.

A true Ufer ground is an specific layout of grounding electrodes.

Most times when people say uffer they mean any concrete encased electrodes.

The NEC describes a minimum for concrete electrode, it can always be more.

Concrete-Encased Electrode.

An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom 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 (? 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.

 

[infinity]

Re: what is a ufer ground

The "Ufer" Ground

The term "Ufer" grounding is named after a consultant working for the US Army during World War II. The technique Mr. Ufer came up with was necessary because the site needing grounding had no underground water table and little rainfall. The desert site was a series of bomb storage vaults in the area of Flagstaff, Arizona.

The principle of the Ufer ground is simple, it is very effective and inexpensive to install during new construction. The Ufer ground takes advantage of concrete?s properties to good advantage. Concrete absorbs moisture quickly and looses moisture very slowly. The mineral properties of concrete (lime and others) and their inherent pH means concrete has a supply of ions to conduct current. The soil around concrete becomes "doped" by the concrete, as a result, the pH of the soil rises and reduces what would normally be 1000 ohm meter soil conditions (hard to get a good ground). The moisture present, (concrete gives up moisture very slowly), in combination with the "doped" soil, make a good conductor for electrical energy or lightning currents.

Ufer techniques are used in building footers, concrete floors, radio and television towers, tower guy wire anchors, light poles, etc. Copper wire does not function well as a "Ufer" ground due to the pH factor of concrete (+7pH is common). The use of steel reinforcement as a "Ufer" ground works well and concrete does not chip or flake as has been found with copper. The use of copper wire tied to the reinforcement rods outside the concrete shows none of these problems.

This is a condensed version of an article on the Ufer. The full article is available here:

http://www.psihq.com/iread/ufergrnd.htm

[ September 27, 2005, 05:07 AM: Message edited by: infinity ]

 

[bphgravity]

Re: what is a ufer ground

Peform a web search for the IEEE Transactions Paper #63-1505 and the IEEE Conference Paper #CP-61-978 by Herbert G. Ufer. This provides the detail study that was performed by Mr. Ufer and submitted to CMP-5 in I believe 1960 after 18 years of study starting in 1942.