paul
Senior Member
- Location
- Snohomish, WA
Re: Cold water ground
The theory on ground rods, the last time I went to a seminar, is that they cover a hemisphere of ground from where the rod emerges. So if you have an 8' rod, you now have a hemisphere with an 8' radius being covered. If you drive your rods closer than 16', their coverage area crosses one another. Therefore, those jurisdictions that have a rule for no closer than 16' are theoretically correct.
Washington state went around some years back and tested several services and not one of them complied with the 25 ohms or less section, so they mandated that you drive two ground rods.
As for the 16' ground rod, by theory you would have more coverage area. Since the volume of a sphere is (4/3)*pi*r^3 you would have a total volume of earth coverage at 8578.64 cu.ft. On two 8 footers you would have 2144.66 cu.ft. of earth coverage. But goodluck convincing your inspector that you just drove it 16 ft down and that it's actually better. You're better off driving the second ground rod at 6' away.
The theory on ground rods, the last time I went to a seminar, is that they cover a hemisphere of ground from where the rod emerges. So if you have an 8' rod, you now have a hemisphere with an 8' radius being covered. If you drive your rods closer than 16', their coverage area crosses one another. Therefore, those jurisdictions that have a rule for no closer than 16' are theoretically correct.
Washington state went around some years back and tested several services and not one of them complied with the 25 ohms or less section, so they mandated that you drive two ground rods.
As for the 16' ground rod, by theory you would have more coverage area. Since the volume of a sphere is (4/3)*pi*r^3 you would have a total volume of earth coverage at 8578.64 cu.ft. On two 8 footers you would have 2144.66 cu.ft. of earth coverage. But goodluck convincing your inspector that you just drove it 16 ft down and that it's actually better. You're better off driving the second ground rod at 6' away.