Grounding for electric service to new barn

[Bruce]

I am installing the electrical service to a new barn and the power co. has agreed to run a service drop from a nearby pole. The barn will have 200amp service and I plan on installing the meter base, service riser, necessary conductors, and service panel myself. A licensed electrician will inspect the work before I call the power co. for the final hookup.

I have placed two 1/2" copper clad 8 foot ground rods along the outside of the barn's sill, about 7+ feet apart. The first rod, which will be right below the meter base, went into the ground like butter. I left a couple of inches sticking up and will drive flush with surface once I install acorn clamp and 4awg copper ground wire.

The 2nd rod, however, was a big pain in the neck. I kept hitting rocks until I finally found a spot where I could drive it in about 5 feet without too much trouble. The next 2.5 feet, unfortunately, were awful and now the rod is sticking up about 3 inches and won't budge any more. The top also has a nice mushroom going from the incredible pounding it took with the sledge. I'll probably have to cut about a

1/2 inch off the rod to get the clamp on.

Two questions:

I know the NEC requires that all 8 feet of the rods be in the ground. How big a deal is it that the 2nd rod is 3-4 inches short of that requirement? Both rods are in fairly moist, loamy clay soil (barn is at bottom of a mountain and about 120 feet from a creek; year round moisture is probably assured as little as 1 or 2 feet down).

The service panel will be inside the barn, opposite the meter base which is on the outside of the barn. Even though the panel will be bonded to the outside ground rods via the service entry cable, I am tempted to install a 3rd ground rod inside the barn along the wall (the barn has a dirt floor for now) and bond it to the ground lug in the panel. The 3rd ground rod will be at least 6 linear feet from two other rods (which will put it about 15 feet from the service panel). Is the installation of a separate ground for the service panel required in something like a barn? It seems a like a good, safe thing to do. And too easy a thing to not do it.

Any other suggestions/comments?

Thanks!

- Bruce bruce at loth dot us

[Joe Bobst]

Review some of the code and practices in texts at your library. For example, dairy barns will often have reinforcing mesh in concrete floors bonded to the grounding system. Grounding metal framing is also recommended. So it's just common sense to anticipate what you may do with the structure and install grounding when its most cost efferctive. Good luck.

Joe