12-15-2009, 11:49 PM
Your choices are:
20' of #4 copper in the bottom of the slab (called a ufer)
#6 copper connected to a 20' piece of re-bar in the bottom of the slab
2 ground rods, spaced more than 6' apart, either driven or buried in a 24" trench.
It used to be common practice at meter poles to have the people drilling the holes for the meter pole drill holes for the ground rods, insert the rods and fill with concrete. Inspectors are no longer accepting this. The code says the ground rods must be "in contact with soil" and concrete is not soil. (The choices in the slab are considered "concrete encased electrodes," not the same as driven ground rods.) So you need to drill the holes, fill with soil, then drive the ground rod. I have a special order 7' long bit I use for this operation, but prefer concrete encased electrodes whenever possible.
Jerry
20' of #4 copper in the bottom of the slab (called a ufer)
#6 copper connected to a 20' piece of re-bar in the bottom of the slab
2 ground rods, spaced more than 6' apart, either driven or buried in a 24" trench.
It used to be common practice at meter poles to have the people drilling the holes for the meter pole drill holes for the ground rods, insert the rods and fill with concrete. Inspectors are no longer accepting this. The code says the ground rods must be "in contact with soil" and concrete is not soil. (The choices in the slab are considered "concrete encased electrodes," not the same as driven ground rods.) So you need to drill the holes, fill with soil, then drive the ground rod. I have a special order 7' long bit I use for this operation, but prefer concrete encased electrodes whenever possible.
Jerry