(This is a carry over from the Mike Holt forum on the same topic.)
Here is a common situation. A residence has a 400 amp service. It is a rural setting, so there is no metallic water main and meter into the house. (It is plastic coming from the well pump). The only metalic piping is the interior water system.
In this situation, the GEC to the made electrode is not required to be larger than #6, correct? Or must it be #2 copper (assuming 3/0 copper parallel for the service), since there is no metallic water main?
It is my understanding that the only purpose of the ground rod is to direct lighting strikes to ground.
[This message has been edited by CTwireman (edited 04-02-2003).]
I know that some would increase the size to #2 if there were two rods installed. The idea is that a rod can only disperse so much current in a given time. Two rods can disperse twice as much current as one, so the GEC ought to be doubled in ampacity as well (in spite of what the wording of 250.64(F) says). Thus #1. Yet, the code only requires a maximum GEC size of #2 for parallel 3/0.
[This message has been edited by Elzappr (edited 04-02-2003).]
CT,- We basicly have the same common here in the rural areas. Our POCO will not allow us to install our GEC in the meter socket, so for a 320 service, we install one GEC, usually a #4 from each panelboard or disconnect to one rod each tail under its own acorn clamp. Then to bond the plumbing, we use #4.
RickG,- Yes you are correct, but due to the fact that the outside water piping is plastic from the well head ,our main electrode is the rod. In town where copper water service is present then we bond accordingly.