This answer is generally primarily based on the United States electrical system, and the reply might fluctuate depending on where you might be.
The NEC code specifies that a strong copper wire used to hook up with a floor rod must be no less than either #6 or #eight gauge (relying on the scale of your electrical service cable). #6 cable cable will all the time fulfill the sizing requirement, although in some cases larger is fascinating. The NEC doesn’t specify a limit as to the utmost length. Of course, shorter is healthier.
Aluminum cable is permissible with bigger minimum sizes, though I’d avoid it due its corrosion properties.
The grounding system serves a few different functions:
So, what resistance to ground do you have to want? The smaller, the higher. The electrical code states that with one ground rod, it must have a maximum resistance of 25 ohms to the earth. In accordance with a Fluke brochure, it is best to attempt to have a floor to earth resistance of less than 25 ohms, or lower than 5 ohms for delicate electrical equipment.
#6 gauge strong copper is approx zero.Four ohm/thousand toes, so having a run of thirty toes will add minimal extra resistance (about zero.008 ohm). However, it’s going to considerably cut back the effectiveness of your system throughout a lightning storm. For one of the best lightning safety, your grounding wires mustn’t have any sharp bends. This is because lightning is a very high frequency signal, and the wire’s impedance increases with frequency. The 0.4 ohm/thousand feet figure is simply valid at DC (zero frequency). While sharp bends don’t increase the DC resistance, it does increase the excessive frequency impedance.
So far as a suggestion, for a “regular” house, I might use strong #four copper to two eight foot lengthy copper-plated ground rods which are positioned 16 ft apart, and pushed in order that they are fully underground. Welding your floor wire to your ground rods is greatest (for instance, with a product corresponding to CadWeld’s One Shot), but “Acorn” clamps are acceptable to use. The welded connection is extra corrosion resistant than the mechanical clamp conection. Also, be sure that your water pipes are additionally hooked up to your grounding system. Your impartial should connect with the grounding system on the service entrance (usually the primary breaker panel), and in no other location.
There’s a restrict on the size of the wire connecting a cable Tv co-ax shield to your own home’s grounding system. It should be not more than 20 ft long, until there’s a further ground rod (see NEC 220.One hundred for particulars), though I’m unsure if this can be the distance to your principal panel, or to your floor rod.
There are lots of other rules that I haven’t talked about (learn the NEC ebook (NFPA 70) or your native code for details). As at all times, use caution when working round electrical systems.