On Wednesday, January 4, 2017 at 8:24:20 PM UTC-5, James Wilkinson Sword wrote:
On Thu, 05 Jan 2017 01:13:23 -0000, Dean Hoffman wrote:

On 1/4/17 6:32 PM, James Wilkinson Sword wrote:

Some cut.

I guess one doesn't test earth grounding with a regular ohm meter.

You guess?

The instructor at one of my code refresher classes asked once if
anyone had
the correct type of tester. No one did out of at least 50
electricians. Earth grounding
is primarily for damage from lightning. He also had a diagram showing
how little current would flow through the earth if a well motor had a
short to the frame. The resistance was so high that there was no way
even a tiny fuse would blow if there was a short.
This is from the meter maker Fluke:
http://support.fluke.com/find-sales/Download/Asset/2633834_6115_ENG_A_W.PDF


"A good grounding resistance is 5 ohms or less" - well since I got 20
MOhms, I guess that isn't grounded.

So did you use an actual ground tester or a volt/ohm meter? It
sure seems odd that
your results don't match Mr. Ufer's and bunches of people after him.
An article in Electrical Contractor magazine says Ufer's grounding
electrodes kept the resistance at 2-5 ohms over a 20 year period.
http://www.ecmag.com/section/codes-standards/what-ufer-ground

Resistance is resistance. Concrete does NOT conduct. WATER conducts. Concrete is a porous material which may or may not contain water. The floor of your house should never contain water, or you have BIG problems, way above a possibility of shock.

--
"VAT is a simple tax..." -- Anthony Barber, Chancellor of the Exchequer on the introduction of VAT on April Fool's Day in 1973.

http://www.esgroundingsolutions.com/...ng-electrodes/

Ufer Ground or Concrete Encased Electrodes

Originally, Ufer grounds were copper electrodes encased in the concrete surrounding ammunition bunkers. In todays terminology, Ufer grounds consist of any concrete-encased electrode, such as the rebar in a building foundation, when used for grounding, or a wire or wire mesh in concrete.

Concrete Encased Electrode

The National Electric Code requires that Concrete Encased Electrodes use a minimum No. 4 AWG copper wire at least 20 feet in length and encased in at least 2 inches of concrete. The advantages of concrete encased electrodes are that they dramatically increase the surface area and degree of contact with the surrounding soil. However, the zone of influence is not increased, therefore the resistance to ground is typically only slightly lower than the wire would be without the concrete.

Concrete encased electrodes also have some significant disadvantages. When an electrical fault occurs, the electric current must flow through the concrete into the earth. Concrete, by nature retains a lot of water, which rises in temperature as the electricity flows through the concrete. If the extent of the electrode is not sufficiently great for the total current flowing, the boiling point of the water may be reached, resulting in an explosive conversion of water into steam. Many concrete encased electrodes have been destroyed after receiving relatively small electrical faults. Once the concrete cracks apart and falls away from the conductor, the concrete pieces act as a shield preventing the copper wire from contacting the surrounding soil, resulting in a dramatic increase in the resistance-to-ground of the electrode.

Ufer Ground or Building Foundations

Ufer Grounds or building foundations may be used provided that the concrete is in direct contact with the earth (no plastic moisture barriers), that rebar is at least 0.500 inches in diameter and that there is a direct metallic connection from the service ground to the rebar buried inside the concrete.



If you bothered to look at your own country's codes, you'd see
that Ufers are one of the allowed types of grounding in the UK.

https://books.google.com/books?id=-1...-02-01&f=false

"Handbook of the Wiring Regulations" (UK)
Based on BS 7671 2001 edition

It's page C2/15, they show 7 types of allowed earth grounds,
two of the 7 are metal electrodes embedded in concrete.

But then you say codes don't matter and you've demonstrated
that you're one of the village idiot trolls, so I'm sure
that won't change anything either.