ECN Forum Forums Code Related Discussion NEC & other Code issues Ground Rod Woes...

Rick,
The rod, re-bar or copper cable for a concrete encased electrode should not be in direct contact with the earth. Only the concrete must be in direct contact with the earth. Metal parts that have direct contact with both the earth and concrete at the same loaction often suffer sever corrosion. "Encased" means to me that it must be covered on all sides.
Don(resqcapt19)

I once fabricated a mount to attach my Hilti core drill to the receiver hitch on my van. It worked great for holes in a line. I just took the base off my mast and bolted the mast to the hitch adapter. I did not have a vacuum hold down unit and anchors are time and money. I traded the core drill for a nice 64 Valient and still have the rig for the van hitch. Anybody around Dallas need some EMT, connectors, couplings, wire, etc? I'm looking for 69 Camaro and 77 Gran Prix parts. Also have a nice 71 Tbird I don't need>

[This message has been edited by gpowellpec (edited 07-13-2001).]

>A 1" hole 100" deep, filled with concrete is not a concrete encased electrode.
Yeah, but it has to be at least as good as a rod driven into rock.

>isn't the rod suppossed to be in direct contact with "soil"?
Say, '66, you'll have to drive your ground rods in a different state. They have to be in soil -- not rock!

>try 45 degrees.
Right. It's a little harder to hit; but easier to get up to. But I never drive a rod straight. If I'm on a slope, I angle with the slope.

Hmmm... Did I mention that it was a double wide? The GEC is connected at the disco which is mounted on the side of the double-wide trailer. Since everything is bonded I'm not sure what I'm grounding nor what you mean...

The GEC is not going to the panel in the trailer...

How do I split up the grounds and keep compliant in both theory and code? Maybe I just don't understand what you meant.

Dspark,

Wouldn't some sort of gear reduction be needed? I can't imagine myself standing on a homemade rig with homemade drill bits spinning at 3600 RPM (assuming 4 stroke, 6000+ RPM for a 2 stroker) and slinging dirt, rocks and other debris everywhere.

My guess is that a post hole driller could be converted with bit extensions or something.



Why not just fill the hole back up with dirt and/or mud?

It's my personal opinon, and no one needs subscribe to it, that Art 550 is probably the most lobbied code in the NEC. This is where terminology intent and theory are fairly convoluted by such influences. 250-32(b) is one casualty of this. Any here who would like to discuss this in length please start a new thread.

Virgil;
today, i took 2 broken sledge heads cause my aim with G-rods is about as good as with my 380 to a welder. He welded on 3/4" rigid. There is a 3' section connected at the head, and a threaded coupling to place anothe 3' section.The obvious intent being a sectional sliding hammer. This $$$ a new welder run insert Beatles Taxman here and a few brews.
I'll inform this thread of any potential cure for blisters

>Wouldn't some sort of gear reduction be needed?
Perhaps. Believe it or not, 3600 RPM is about 11 MPH, and even 6000 RPM gives 18 MPH. It is not real wicked.

>Why not just fill the hole back up with dirt and/or mud?
Where are you going to get it?

Seriously, I think that driving a ground rod is supposed to make a tighter soil contact. I was going to compensate with mortar and lime which would supply more free electrons, retain moisture, and not leach away.
You could dope the mortar with something else too, a little copper sulfate or something... you know, just so you could say that the end product was at least equal to a driven rod.


[This message has been edited by Dspark (edited 07-15-2001).]

>He welded on 3/4" rigid.
That's a great idea.

>There is a 3' section connected at the head
I guess you still have the drive the last 3' with a regular the sledge. Did you get a tee handle on it too?


And you know not to try to use your sliding hammer as a sledge now, right?

Now wait a minute there Dspark, I'm pretty slick when it comes to mechanical things (anyone want to talk aerodynamic theories? Coefficients of drag, Cd 's of lift, Reynolds numbers, gyroscopic precession, etc.?.. I can prove that I know what I'm talking about here...)

Any wobble at all at the end of the bit before it strikes the ground will cause it to self destruct at those RPM's when you're dealing with this kind of mass.
Especially if the point of attachment is a swivel point instead of a solid attachment.

PTO's are typically 540 RPM and post hole diggers are typically a good 4:1 reduced from that. I've seen post hole diggers start to wobble and begin the self-destruct routine even at those low RPM's. Makes a lot of noise...

How did you determine MPH?

MPH compared to RPM is a little vague without something to relate them... Are you measuring the stroke of the piston? The outer circumference of the bit? It has little consequence on the energy built up it a spinning mass. Especially a heavy one.

The spinning mass would cause a gyro effect and everything would be fine until a force acts upon it, (like moving it towards the ground) then this thing called gyroscopic precession causes the force to act at 90º to the plane of rotation and in the direction of the rotation. Gyroscopic Precession is of extreme importance in aircraft design and useful in aerobatics (lomcevak) . In other words, the slightest force acted on the bit will cause it to wobble violently (and the forces will be proportional to the square of it's velocity, double the velocity, quadruple the forces).

Also, with the tip spinning at such rpm, the tip would probably just melt away from the friction of the stone. Gotta be a slow grinder, less than 1000 RPM range...

I'd gladly watch from a distance the testing of such a machine... video camera ready...



[This message has been edited by sparky66wv (edited 07-15-2001).]

But we're allowed to lay them in a 24" trench... Do they assume that the weight of the loosely compacted soil 24" deep is enough "pressure" on the rods?