Concrete Encased Electrodes (CEE/UFER).

 Concrete Encased Electrodes (CEE/UFER). Leavenworth Real Estate Inspection

I was asked to write a little background on Concrete Encased Electrodes (CEE) or what is referred to as a “UFER Ground”. This is a grounding method that was developed during WWII to provide an electrical earth grounding method in dry areas. Most grounding systems rely on moisture and pH in the soil and to create a low impedance path to the earth. The “UFER” technique uses the construction of concrete foundations to create a low impedance alternative for grounding.

Concrete has a high pH (known as a base chemically). Concrete also absorbs moisture very quickly and releases moisture very slowly. Herbert Ufer realized that this means that concrete had a ready supply of ions and so provides a better electrical grounding path in almost any type of soil.

Grounding (and bonding) is maybe the most overlooked and misunderstood part of the electrical systems. The main reason for grounding in electrical systems is safety.

Grounding is a bit misleading. The term for most purposes means earthing or connecting the circuit to the earth. But really it is connecting the circuit to a common point of reference which in most cases is the earth.

This brings us to impedance and its effect on the grounding system.

Impedance, in very simple terms, is resistance occurring in AC electrical circuits.  The degree of resistance is measured in units known as ohms.  The lower the impedance, the easier it is for electricity to flow through an object.  For utilities they are looking for grounding system that are 1 ohm or less and most commercial facilities are looking for 5 ohms or less. For residential ground rod the NEC requires 25 ohms or it must be supplemented with another rod. But here is the catch; once a second rod is installed they do not need to confirm that it has a resistance of less than 25 ohms.

Enter the CEE or UFER ground. It has been shown that the “UFER” ground achieves 5 ohms or less.In 1942, H.G. Ufer performed an 18 year study on the resistance of concrete-encased electrodes. At the end of the study in 1960, the average of 24 installations was 3.57 ohms, none ever exceeding 4.8 ohms over the 18 years. The best reading was 2.1 ohms.

Now for a little more about electricity and how it travels. The notion about electricity following the path of least resistance is actually incorrect.  Electricity will follow “all paths” back to the source, but it will follow paths proportionally according to the conductivity of each path.

So when impedance increases even slightly, the electrical current seeks other paths to ground.  When electrical path in the grounding circuit is greater than a person in contact with an energized material it can and will travel through that person. So having a low impedance path to ground is crucial.

The grounding system is for protection of people, equipment and fire. This goes hand in hand with overcurrent protection. For the protection to work properly they must installed correctly and be fast enough to eliminate or minimize damage. This is why it is so important.
 

“Real knowledge is to know the extent of one's ignorance. “

Confucius

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