Joe,
     Remember the conductivity of the ground is very dependent upon the=20
amount moisture in the ground. Very dry soil with no iron in it is a=20
very poor conductor. Our ground here has a lot of moisture in it and it=20
also has a pretty high iron content. So in most cases a single eight=20
foot copper rod will work fine.
     Two reasons for bonding the water pipe to the ground wire and the=20
breaker box is that one it helps with the ground connection to earth and=20
two it insures that the water pipe and the house ground are at the same=20
potential. If the water line is made out of plastic bonding is not required=
..
     There is a ground wire running on the poles that deliver power to=20
our homes but it is not directly connected to the house. There is a drop=20
line that runs down the pole and it is connected to a ground rod that is=20
driven in to the ground. The transformers supplying power to our houses=20
is a single phase unit that drops the primary power to a split single=20
phase 240 volt secondary going to the house with the neutral connected=20
as a center tapped lead. This gives 120 volts from each hot wire to=20
neutral and 240 volts across the two hot lines.
     The standard installation is now 200 amps but there are still a lot=20
of 100 amp units out there and a few 60 amp units. In fact there is=20
still a hand full of 40 amp services but they are very rare now.
     When I upgraded my house I had a 500 amp service. There was a 200=20
amp GP service in the main house, a 200 amp GP service in extension of=20
the house, and a 100 amp heater - air conditioning service.
Thanks,
rich!

On 7/12/2014 12:47 AM, IVP wrote:
>>      In the US the ground wire is bonded to at least one copper rod that
>> is driven into the ground on the outside of the house
> My NZ-registered nephew tells me that here they are considering or
> now earthing at the distribution transformer, and so each house will
> need an earth wire as well as the single-phase pair. Apparently "NZ
> earth is not good"
>
> Joe

--=20
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