What must never be used as a grounding electrode or grounding source are steel rebar in a swimming pool, aluminum, metal underground pipe systems and metal water pipe systems.
Acceptable electrodes for grounding electrodes are rods, pipes, mats, tapes, wires, plates and structural steelwork that is either buried or driven into the ground.
The pipes of other services such as gas and water must never be used as grounding or earth electrodes although they must be bonded to earth.
The reason why 2 ground rods are required is to protect the homes or building's electrical system from any lightning strikes, power surges, voltage spikes, static electricity and other faults in the electrical system
Having 2 ground rods is always better than one to ensure the electrical current can flow into the ground when needed.
Ground rods also protect against static electricity from the earth, electric utility and other sources and provide a place for lightning's electricity to dissipate.
Ground rods also ensure that any and all earth ground connections get around the same voltage spikes during a power surge.
The National Electrical Code requires you have a minimum of 2 grounding rods, unless the one ground rod has a resistance to earth that is less than 25 ohms.
The reason why grounding rods are not insulated is because the grounding rods have to be in direct contact with the earth to be able to dissipate the electrical current properly and effectively and provide for a safe path for any fault currents to flow.
If the grounding rods were insulated it would prevent the crucial connect to the earth with the ground rod and hinder the ground rods primary function.
Another reason for grounding rods to use a bare copper conductor below grade of the earth is to maximize the current leakage capacity and to also maximize the sphere of influence of the grounding system.
The reason you should not use the ground as a neutral is because the neutral and the ground have different functions in the electrical system.
The neutral wire in an electrical system is what carries the current back to the source and the ground wire is designed to protect you and appliances, circuits, house etc against electrical faults.
The ground provides a path for current to flow to the earth in case of a short circuit and should have no voltage on it
Connecting the ground and neutral is sometimes done but ideally it should not be done as it can create a dangerous situation in which the ground wire becomes energized and lead to a shock hazard.
Copper is used for grounding because copper is a good conductor of electricity and also has excellent resistance to corrosion.
These reasons make copper an efficient and durable metal for safely dissipating any electrical current into the earth.
The great conductivity of copper ensures that any electrical current can easily flow through it and into the ground and effectively and safely divert the electrical surges or faults away from people and electrical systems.
Copper also will not rust even when buried in the ground for a long time and is why the earthing system for electricity is called the copper rod earthing system.
It is safe to touch a ground wire as long as there's no short circuit to ground.
In a normal operating electrical system the ground wire is not energized although the ground wire can become energized if the hot wire makes contact with the ground wire or neutral wire.
A breaker is supposed to trip in these cases but it doesn't always happen so you have to be careful.
Even the neutral wire can be touched without getting shocked as long as there's no electrical fault.
You can use any copper wire for grounding but you should mark the copper wire as a ground wire on both ends if you use another color of copper wire other than green or bare wire.
It's best to use either green colored wire or a bare copper wire for grounding for easy detection of the ground wire but other wire can be used as long as it's marked as a ground wire.
The reason why old houses do not have ground wires is because in the old days when the old houses were built there was no electrical code that required a ground wire.
The electrical codes when older houses were built does not require any grounding of the electrical system so they didn't have ground wires.
Houses built before the electrical code changed to include a required ground wire did not need a ground wire so it was not installed.
The electrical wires in those days also didn't even have ground wires like the new wires of today.
The old houses also only used the two prong electrical outlets without ground which were all that was available at the time.
The National Electric Code or NEC did not mandate or require any grounding in all electrical circuits when the older houses were built so many older homes were simply wired without any grounding or ground wires.
The absence of a ground wire is often associated with having 2 prong electrical outlets that only provide a hot and a neutral wire and no grounding path.
Having a lack of grounding wire in the electrical system can pose a safety risk and even more so with modern appliances that have metal casings which can be come energized in case of an electrical fault.
If you live in an house that has no grounding on the outlets and other electrical circuits it's best if possible to get the wiring up to code and install grounding. '
In some cases all you may need to do is upgrade the outlets and install an additional grounding wire.