Driving Ground Rods
All electrical wiring must provide a return path to the earth for the electrical current. This is referred to as “grounding.” The purpose of grounding, or the return path to earth, is to prevent flesh and bone from inadvertently providing that path. (an uncomfortable and frequently fatal instance) Until recently the most common way to provide that return path to the earth was the installation and use of ground rods.
Some jobs, where heavy metal beams were installed upright in concrete, allowed you to use the upright metal beams as a grounding means. There are a few other options to the ground rod available, and of late the NEC encourages using a metal rod encased in a concrete foundation as a path to the earth.
A typical ground rod is 5/8” diameter and 8 feet long. Knowing what is beneath the surface of the earth 8 feet down is not easy. Usually you have no real idea. The earth can be completely free of rocks, or it could be filled with small rocks, large rocks, boulders or other unknown objects installed and then forgotten. Sometimes ground that is completely free of rocks can be compacted so much that it is as unforgiving as concrete. In other cases, ground that is filled with rocks has been recently disturbed and provides an easy ground rod driving experience.
There are locations and situations where you are permitted to lay-in a ground rod in a ditch and bend one end of the rod up towards the surface. There have been times when the ground was so rocky I have had to do that. One time I was driving a ground rod, successfully, until it was about 7 feet in the ground. Then I hit substantial subsurface basalt. It would not allow the ground rod to go any further. Since that time I have made it a practice to drive a ground rod at a 45 degree angle.
One location in the Spokane area, on a mountain side, had numerous ground rods sticking out of the ground all over the property. They were all exposed about 5 feet out of the ground. I guess they had a difficult time getting 8 feet of ground rod driven.
There have been a few times that I have tried to “save” an unused/unneeded ground rod by pulling it out of the ground. One time I had a guy on a back-hoe pull one out for me. When it came out it looked like a wet noodle. It must have gone around 4 large rocks as it went down. Since you can’t drive a bent ground rod, it would have been just as useful to abandon that one.
There was one instance where, to provide grounding, I had to run 50 feet of copper wire to a steel well casing. The well casing had been in the ground for many years. When I tested it I found that the grounding efficiency would not allow me to run a 100 watt bulb using the well casing as a ground. However in that particular case I was grounding a transformer that used less than 100 watts, so I let it go.
When I first started driving ground rods, by hand, I used a sledge hammer. Then I decided it was easier to use a steel fence post pounder. Either way can be dangerous to the operator’s health. One time when pounding a ground rod, one of the guys took such a big swing that the fence post pounder over balanced on the upward swing and came down on his head. Another time the pounder came off the top of the ground rod, went a little to the side and on the downswing the guy’s hand got caught between the post and the pounder. It ripped up his knuckles pretty good.
Lately we have made good use of powered impact drivers to drive ground rods.
We like that better.