Earth Electrodes and Drilling

One method is to use a gelling agent and an electrolyte down this three meter hole. This will wet and gel a large cubic volume of earth. An inert gelling agent that melts when hot and a salt electrolyte would do. You pour it down the hole it gets cool and gels and you have a very large contact area.

what do you need this for? Radio Antenna or eath for mains

It will depend on your local regulations, but realistically speaking ,if you can guarantee <0.5 ohms to earth all year round it should be ok.

Codes permit 1 ohm.If you can achieve 0.5 Ohm,there is no need to take any further action. The basis is at higher values of earth resistance, fault current generated will be low, lower than protective device setting. In such cases earth fault protection may not operate. Therefore, concern should be whether at the available earth resistance value, system can generate enough earth fault current to allow operation of the protective device.

Sir How to get a feel of the value of Earth resistance significantly affecting the earth fault currents? In case of E/F relays we normally set them at 10%(how will the case be if only HRC fuses are being used?) Now my the contractor is claiming that the Earth resistance is measured to be 0.9 Ohms and he needs @0.3 Ohms for electronic equipments and henmce he has to touch the water table 80 feet below. I personally felt the earth resistance of 0.9 ohms itself is quite low and ideal and further lowering the resistance to 0.3 Ohms is uncalled for? Further can i suspect faulty measurement / recording on my contractor's part? Pl respond. regards

When you add a ground rod,you are merely adding another component to the electrical grounding system.On the bottom of every power pole, is a coil of #6 copper wire, in a spiral, and it runs all the way up the pole to the power company ground wire.Every pole in the United States is tied together in what is called a MGN (Multi-Grounded Neutral) system. The neutral wire going to your house is connected to this ground system.The idea is to minimize total ground resistance.All metal parts of a building are required to be bonded together to reduce any difference in potential between any two metal parts of the building.In the main panel, a bonding jumper must be installed, which bonds the neutral and equipment grounds together.A sub-fed panel must NOT have the bonding jumper installed. (Which is why a mobile home inside breaker panel has the bonding lug removed) The NEC frowns on multiple ground rods, unless they are bonded together, because multiple ground paths can create differences in potentital and unpredictable current flows, and hence dangerous voltages.Now.Clear as mud?

Obenay N. Pebvk

Check out this link for info on NEC regs and some testing done recently on deep ground rods.

http://www.cpccorp.com/deep.htms.

Obenay N. Pebvk

correct link = http://www.cpccorp.com/deep.htm

I often run across comments that appear to confuse issues regarding the "required" resistance "to earth" of the earthing/grounding electrode system. First, it is a system. Every metal item properly bonded together reduces the resistance "to earth" which is why NEC requires things like rebar in the slab and metal water piping to be connected, and most commercial building distribution plans typically show some quantity, such as three, of the standard "ground rods" with them all connected by exothermic-welds to the GEC, in addition to a generic statement like "ground/earth testing must be documented to reach <10 Ohms resistance to earth."

Any resistance better than 5 Ohms is all you need for really good lightning and surge protection, anything better is generally only useful for ultra-sensitive electronic signal processing - with layers of noise filtering likely installed as well.

And in case you get any questions or comments noting your breakers or fuses; no, the earth-resistance at the Grounding Electrode Conductor has NOTHING to do with opening a circuit by clearing overcurrent protection devices in case of a line voltage-to-case fault...that's the job of the equipment bonding conductor in a grounded system.

That's why you can't just drive a ground rod at each piece of equipment and forget to install a grounding(bonding) conductor...unless you wish to shock anyone stepping on your metal handhole or any dog peeing on your streetlight.

I prefer to say that you have twice as much glass as you need, so it is an inefficient glass design.

Refer back to my comments #8.There are cases where you DO NOT bond the grounding electrode and the Neutral conductor, and if you do, you are creating the very hazard that you are trying to avoid:A difference of potential between any two points of possible contact.

An efficient ground at 60 hz. is not nescessarily a good ground for DC voltages, due to the capacitive component, and not nescessarily a good ground for high frequency because of the inductive component. The national electrical code specifies 25 ohms as the minimum, using a 3 point system.

We could pick this subject apart ad-naueum, but for all intents and PRACTICAL puposes, use the 2005 NEC as a guide, or consult a licensed electrician.

As the old farmer said about the guy that drove his truck into the pond:

"I don't understand it.It only came up to their chest on my ducks!"

This subject, also is deeper that it looks to the layman.

Not trying to trample any egoes,and my apologies if anyone feels so inclined.

Obenay N. P.