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How do you get a ground rod to 6 feet ?
That caliche must be something else. I've never heard of it. But I must question either your selection of ground rod, or method of insertion. I've sunk a number of ground rods in semi-rock.... sometimes penetrating granite too. We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel rods. We also used rotary impact hammers to drive the rods down.... often right through a rock or whatever. Worked almost all the time, and did not "mushroom" the top of the rod. If a 3/4" pointed solid steel rod can not be driven through Caliche with an impact hammer I can't imagine any other tool short of dynamite doing the job. Ed K7AAT |
How do you get a ground rod to 6 feet ?
Dave Lemper wrote in message ... The soil in central Texas is called Caliche with a lot of clay, CaCO3 & shale. Attempting to drive in a ground rod yielded only a mushroom on top & blisters on me. Local tool rental place has concrete bits, but maximum length of 18 inches. Possibly longer bits are available in a larger city. Renting a back hoe is out. Any suggestions appreciated. Dave WB3DWE Here's a snippet from the state of Washington's website that quotes the NEC: NEC 250-52 (c)(3) (1999 edition) requires that ground rods "be driven to a depth of not less than 8 feet (2.44m) except that, where rock bottom is encountered, the electrode shall be driven at an oblique angle not to exceed 45 degrees from the vertical or shall be buried in a trench that is at least 2½ ft. (762mm) deep." The requirement is that the rod be driven to a depth of 8 feet. If the rod cannot be driven then there is a choice of either driving it at a 45-degree angle or laying it in a trench that is not less than 2½ feet deep. http://www.lni.wa.gov/tradeslicensin...ts/elc0210.pdf. I browsed some newer discussions and found nothing newer to be at variance with the quoted material. The current NEC is $75 if snippets won't do ya'. http://www.nfpa.org/itemDetail.asp?c...RL=Pub licati ons/ You need 25 ohms maximum rersistance (three-point method) to say you have a good ground. |
How do you get a ground rod to 6 feet ?
Fred McKenzie wrote:
In article , Dave Lemper wrote: The soil in central Texas is called Caliche with a lot of clay, CaCO3 & shale. Attempting to drive in a ground rod yielded only a mushroom on top & blisters on me. Local tool rental place has concrete bits, but maximum length of 18 inches. Possibly longer bits are available in a larger city. Dave- Last year there was a discussion here about sinking a ground rod using an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian White, GM3SEK, who proposed that method. The other point was that SDS+ bits are available up to 1.0 metres long, so by using both rotary and hammer action you can drill a pilot hole through most kinds of rock down to that depth. There is also an article at http://www.n4lcd.com/groundrod/ that proposes a slightly different method of coupling the hammer drill to the ground rod. The question is whether Caliche can be penetrated by such a method. Has anyone tried it? We don't have caliche here, by that name, but from accounts on the web I'd doubt if it could be penetrated by hammer action alone. However, it seems more likely that an SDS+ bit could drill through it. Another consideration is whether or not there is moisture in the soil below the Caliche. If not, then it might not provide a low-impedance ground even if you could penetrate it! That is certainly the problem at this QTH, where an earth rod drilled and hammered into the very rocky subsoil produced a resistance of 500ohms! Long horizontal electrodes are the only kind that work at this QTH. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
How do you get a ground rod to 6 feet ?
While I don't have any 'caliche' on my property, I am blessed with a
lot of randomly placed rock. Driving any ground rod to about 6 feet is a guessing game more than anything else. I've found that ground radials are more practical. Not easy, just practical. They seem to work as well as any ground rod I've ever used (better in some instances). The local power company is supposed to put down ground rods for safety. Having seen some of their methods, I'd tend to go with the radials (ground wire attached to water pipes... PVC water pipes, great idea huh? And, NO, I'm not kidding.) - 'Doc |
How do you get a ground rod to 6 feet ?
On Sat, 23 Aug 2008 10:58:19 -0500, Dave Lemper wrote:
The soil in central Texas is called Caliche with a lot of clay, CaCO3 & shale. Attempting to drive in a ground rod yielded only a mushroom on top & blisters on me. Local tool rental place has concrete bits, but maximum length of 18 inches. Possibly longer bits are available in a larger city. Renting a back hoe is out. Any suggestions appreciated. Dave WB3DWE I have a Glen Martin ground rod driver (fashioned after a fence post driver) that worked fine in Houston. In San Antonio, it only drives a rod about one foot down, then muck... I ended up just driving a short rod, mainly used as a connection post, and then I extended several long, buried wires out from it. bob k5qwg |
How do you get a ground rod to 6 feet ?
I got a better ground than using a stake by doing something a little
unorthodox. I buried an old channel 6 yagi antenna in under six inches of earth. It made a pretty good ground. It was a lot better than a stake. Michael Dave Lemper wrote: The soil in central Texas is called Caliche with a lot of clay, CaCO3 & shale. Attempting to drive in a ground rod yielded only a mushroom on top & blisters on me. Local tool rental place has concrete bits, but maximum length of 18 inches. Possibly longer bits are available in a larger city. Renting a back hoe is out. Any suggestions appreciated. Dave WB3DWE |
How do you get a ground rod to 6 feet ?
Dave Lemper wrote in :
The soil in central Texas is called Caliche with a lot of clay, CaCO3 & shale. Attempting to drive in a ground rod yielded only a mushroom on top & blisters on me. Local tool rental place has concrete bits, but maximum length of 18 inches. Possibly longer bits are available in a larger city. Renting a back hoe is out. Any suggestions appreciated. Dave WB3DWE Dave, If you truly cannot drive an electrode vertically, then you will need to consider drilling for horizontal electrodes in trenches chased into the rock. Drilling creates another problem, backfilling for conductivity. Electrodes in dry rock might not be very effective. I have had success in driving electrodes into moderately shaly ground, and even very dry clay isn't too difficult. Pointed 19mm copper clad steel rods or stainless steel rods are a lot easier to drive into hard stuff than smaller sizes. The following article shows some of the equipment that I have used sucessfully, and likely to be more successful than using an ordinary hammer. Machine driving does not mushroom then end of the electrode near as much as hand hammering. http://www.vk1od.net/post/driver.htm Owen |
How do you get a ground rod to 6 feet ?
"Wayne" wrote in
news:BdXrk.527$482.222@trnddc06: As a last resort I will hack a trench with a pick and lay in the rod at a shallow angle to the surface. Would this give an adequate ground ? I could also bond it to an outdoor brass spigot 10 yards away or even to an anchor fence in the other direction. Dave WB3DWE - In my opinion the trench would be ok, but I'll leave that to the experts on the group. However, I remember chiseling through the caliche to be annoying, but not that difficult with the right tools. It can be done with a "shooter" style shovel, but that is a bit more effort. However, I doubt if you would ever get a copper rod driven through without some major damage to the rod. If the soil is permiable to water, you could try another of my hack methods. Sweat a garden hose connection onto a piece of copper tubing. Attach a garden hose to the fitting, and point the rod down in the place you want to sink int. Then let it rip. In my area, we have a few inches of topsoil, than a really hard clay, then rocky clay, followed by sandy clay/sand. It will even move some rocks out of the way. The tubing becomes the ground rod of course. - 73 de Mike N3LI - |
How do you get a ground rod to 6 feet ?
Ed,
"Ed" wrote in message . 192.196... We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel rods. We also used rotary impact hammers to drive the rods down.... often right through a rock or whatever. Hammer-only mode? Or "rotate & hammer" mode? ---Joel |
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