I bought a ground rod driver bit for a TE72 roto hammer the other day. Finally got to use it this morning. SWEET. Carrying that big Milwaukee up the ladder was the hardest part. I managed to get 7’4″ of rod in the dense clay ground in about 2 minutes before hitting rock. I’ll have to drive another rod to get past the inspection.
I have a slide type driver and of course the old standby sledge-o-matic, but this driver bit is going to send them into early retirement.
Kind of pricey at $70.00, but the time saved, as well as the reduced risk of injury means this puppy has a new home.
Dave
Replies
I managed to get 7'4" of rod in the dense clay How much rod do you need in the ground?
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
my guess is more than that..lol
I think it's 8 feet..but not fer certain..
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Repairs, Remodeling, Restorations.
Ground rod has got to go full in--that's ten feet!
I drive two 5/8" by 10' rods for every service I upgrade. I use a "groundhawg" which uses an auger point for the rod and a circular chuck driven by a Milwaulkee holehawg. See
http://www.groundhawgs.com/
And FYI, the operator in the website photo does not come with the unit.
The system punches a rod through hard pan real well. The cool thing (besides not having to climb a ladder) is that I can back the rod out if it hits a rock.
Cliff
p.s. those of you who drive ground rods--do you call your utility locator service every time you sink one?
What does that cost?
This particular rod is for my shop. I'll drive a second rod later this week, after the rain rain blow through here.
I guess you could call this clay hard pan. I am not enough of an agronomist to tell what variant it is. Once it has dried out, you have to dig through the top 4" to even get a 2x4 stake started with a 14# sledge-o-matic. Ussually I can pull a groud rod or steel stake with a 24" pipe wrench, but not in this stuff. I use the bucket on my tractor and a length of chain for stakes, but the ground rod would likely bend if I tried it. Besides ther is a 99% probability of hitting another huge rock at that depth 6' away from the first rod. Rocks are from 1'6" to 4' thick and from the size of a small coffee table to the bed of a pickup truck.
Dave
Cliff,
In my corner of the world I don't think anyone ever calls the utility locators before driving a ground rod.I always look for where the gas line and water line enter the house first though.A co-worker told me that one time he was doing a residential service change and just as he was putting the tools back in the truck, the homeowner came out and asked if he could turn the water back on.He told her that he hadn't touched the water service,but,after looking around he knew what had happened.He had to dig out an 8 ft. hole by hand,big enough to work in,so that the city could come out and replace a section of water pipe that he had driven the ground rod into.He said it didn't even break the pipe,the end of the rod just squeezed the pipe flat without spilling a drop.That cut out section of pipe hung from the ceiling of our shop for some time as a reminder to everybody else to "think before you drive".
Barry
Edited 4/22/2004 10:23 pm ET by IBEW Barry
Do you know (and can you tell if you do) what the conductive slurry powder is that Groundhawgs sells to decrease the resistance between the ground rod and the soil? If not, does any one have some suggestions on the best way to make their own?
Barry,
Yea, I rarely call locate either--only if I'm in an area where I know there are petroleum/nat gas supply piplines. Otherwise, I just look for the water service valve and the sewer cleanout, project the pipes paths, and go for it. Hand digging 8 feet--ouch.
Casey, I have no idea what the conductivity-enhancing powder is. I suppose I ought to ask Groundhawgs for an MSDS.
You can buy commercial products to do the same thing. Don't know what those are either.
Cliff
Used to be in some critical situations where grounding was difficult people would sometimes drive a well made of copper pipe. 2" is common. This copper pipe would be capped so it wouldn't fill as it was driven and it was drilled along its length every few inches. The top was left above ground and a movable lid attached. Alternatively a small dry well or moat was installed around the normal ground rod.
Into these they would pour copper sulfate or similar chemical filling the pipe or containment. Moisture in the ground would enter the holes and dissolve the filling. This then would flow back out and down the pipe greatly increasing the conductivity of the soil and the rod to earth connection.Over time the filling would have to be replaced. This was regularly done, typically, every few years.
Problem is that the chemicals used (Copper sulfate, magnesium sulfate or common rock salt with magnesium sulfate being preferred as it is least corrosive - per Electricians Handbook 1970) while not very toxic certainly wouldn't do anyone any good if drunk. Idea being that each of these pipes is basically a tiny superfund site slowly saturating the surrounding soil with the chemical used.
There are a few down sides besides the environmental end. One being that in chronically dry soil, one of the major reasons earth conductivity is so low, there may not be enough moisture in the ground or air to effectively dissolve the crystals. Also if you forget to recharge the pipe regularly it can run out of the chemical and become much less effective. Idea being that in some ways a ground you can't count on, one that's not there when you need it, is worse than a consistently poor ground connection.
In most situations the actual resistance of the rods is not an issue electrically. No matter how poor the connection the code only demands two. This is a nod to the reality of how poor these ground systems are as a current path for return current. The rods are usually only functional as ground paths for lightning or massive surges. Even massive ground grids act primarily as ground planes, for high frequency currents and to maintain equal potential around a building, not an effective alternative return path.
In the 1999 NEC, it's 8 feet (NEC 250-52(c)).
Maybe I'll break down and buy the 2005 NEC in a few months.
r--
No reason to buy the 2002 NEC yet. You're right, the Code requires ground rods to be 8 feet long.
My bad. I musta been thinking of the criterion of 10 feet of underground metal water pipe as a grounding electrode...
Those rods seem longer than 10 feet, even, when you're using a manual driver. I had a pile-driver style one welded up by a guy on my crew, and it was was pretty effective. The FNG gets to drive the rods, and I got tired of losing helpers--and abandoning rods after cutting 'em off with 5 feet under and 3 feet above ground. It isn't worth the time to pull 'em when they're in more than half way. Not with the hard pan hanging on to them.
Our hardpan out here in the Sacramento/San Joaquin Valleys is like a one or two foot thick layer of almost-hardened cement about 3-5 feet below grade.
The groundhawg system is not cheap. It's been a while since I bought it, and I paid less than list price (got it at a trade show for sparkies). Think it was $350 for the unit, and of course you need a hole hawg to run it. The auger tips are couple of bucks each. Real money, but time is money, and I can spin in an 8 foot rod in one minute with the thing.
I've never worked on a site w/o power of some sort, so that's never been an issue. In fact, the groundhawg comes in real handy when I set construction power poles--use a genset to run the drill motor and spin in a rod (our AHJ says one rod is enough for a temp service). Then, when I strike the temp power set up, I can back the rod right out (most of the time).
Cliff
Just bought two more rods today. One for the shop and the second for the new studio/kennel blg. going up next to the shop. Both 8' rods.
10' rods are available also.
We use mostly 10' at the utility company I work at. When a crew sets a pole they staple #4 solid copper to the side before it goes in the hole. If it is a transformer bank pole, it also gets a driven 10' ground.
Dave.
I'm definitely skipping the 2002 NEC. I'm getting stuff in the mail about the 2005 edition, so I assume it will be available in a few months. Then Holt, Shapiro, etc... can advertise $1000 seminars to explain the stuff they wrote into the code deliberately ambiguously !
Where Mr Hilton is, you just about need an AtlasCopco rock drill for much beyond 3' of depth.
I'm surprised that I don't see more "trenched in" (i.e. horizontal) rods used in the Austin/SA region to meet any NEC for grounding.Occupational hazard of my occupation not being around (sorry Bubba)
$70 sounds a little high.
Still a good buy in the long run. On longer, sectional rods, especially.
For residential work I usually go manual and use a 3lbs engineers hammer. A lot of locations don't have power and the ground is usually relatively soft. Used to use a driver I welded up, a section of 1" pipe about 24" long with two pieces of 3/4" welded on parallel with lead shot added for power, but it wandered off. Guess they liked it more than I did.
Commercial work, with many rods and longer ones, really goes a lot smoother with the driver on the rotary hammer.
A friend of mine used to install TV transmitters and recording studios. He made ground rods 40 - 60 ft deep using 3/4" type K copper pipe. His method was to sweat a 3/4 NPT female to the top end, and hammer the bottom shut and poke holes in the side of it. Then water from a garden hose was all it took to sink the rod. Only thing is, you can't stop or you're dead. Rocks up to about basket ball size would eventually get eroded around and pushed out of the way. He got some prehistoric seashell fossils washing up out of holes on Mt. Wilson.
-- J.S.
Hadn't thought of manufacturing my own sectional rods. I suppose if the specs didn't say otherwise I could. I have always bought the solid rods with the threaded ends. Fasten on tip and drive until a few inches shy of the ground, add another section and continue until I meet spec.
Dave,
I agree 100% on the ground rod driver for the roto-hammer,after you use one you NEVER want to drive one with a sledge again.Of course the last time I offered to help a friend change his service on the weekend, somebody else had the driver locked up on another job.I ended up driving the rod by hand and it sucked out loud.I can remember being able to drive them almost all the way without stopping when I was 25.Now...not even close.
Barry
Probably not kosher, but I used an old 15" long 5/8" spade bit on an 18" extension to loosen the soil so I could at least get the rod down to a decent height for driving with a sledge.