Quote Originally Posted by Want2build1 View Post
"Combining both of them wouldnt be a good idea."
Interesting question. Theoretically your generator has 3 phases all off earth. The three phases are divided up between the houses at your substation to try and equalise the load. Your single phase earth connection comes with your mains supply and you back it up by connecting it to a water pipe. The local ground is probably thus already in place, no spike required.
The earth resistance is noted on the house certificate, usually calculated by distance and square mm rather than by measurement. The distance is measured back to the 25mA breaker which is why you see a lot of fat naked copper heading for the fuse box. Overkill makes the sums easy.