installing an earth ground in garage

[kel fab creations]

So I just got my new Longevity 60i plasma to go on my plasma table and found out that I need an earth ground now. I've read that earth grounds are a 10 foot copper rod driven into the ground. So how the #&$% am I gonna do that in my 3 car garage? Is there an alternative grounding method?

[kel fab creations]

What am I looking for at lowes? 1/2" solid copper rod?

[BrianMick]

The old rods used to be solid copper, but now they just copper coat them, You should be able to find them at any building supply store...
Brian

[pony]

A true earth ground, as defined by the National Electrical Code, consists of a conductive pipe or rod driven into the earth to a minimum depth of 8 feet.

I have driven lots of ground rods to accommodate my electric horse fence. They go in fairly easily with a large 6lb lump hammer, even in summer baked Texas dirt. The only problem I foresee is if you hit rock. If I hit rock I just drive the post a few inches over, but your garage could end up looking like a piece of swiss cheese.
I don't know why you couldn't drive the rod outside and drill a hole through the garage wall to feed the wire to your machine. A good earth ground is dependent on soil water content, the dryer the soil the less the rod conducts. I position mine next to the horse water troughs, and the one at my horse barn near the water gutter down spout. I always check the resistance in dry 'worse case scenario' weather. If you don't have a resistance to ground of 25 ohms or less using one ground rod, you must use a second supplementary rod.

If you have a metal water pipe that extends out of the garage in to the dirt then this could also be used as a true earth ground, along with a grounding rod. The 2005 National Electric Code requires that you bond your electric service to a metal water pipe if one exists.

[kel fab creations]

So I drilled the hole and drove a 5/8" 8ft copper coated rod in with about 5" sticking out at the top. Connected a 2 gage stranded wire from the ground clamp on the plasma to the rod and now as soon as it strikes an arc the controller disconnects. (Used to get through one cut). So I hooked a 12 gage wire from the controller case to computer case to rod and no change. I was excited cause the rod wasn't that hard to put in but now this thing is driving me crazy. Where do I go from here? Thanks for all your help so far.

[SCHIDTHEAD]

ground your plasma to your material or table bed and gound your plasma case and table to the earth ground.

[pony]

So, can someone explain why you ground your material (not just the ground lead, but a real ground). Remember, I'm a newbie, I'm not questioning anyones suggestions, I'm genuinely seeking advice.
My plasma cutter will not cut if the material is grounded to true earth ground as well as the cutters ground. I found this out by accident when I found my plasma cutter would not work and I thought it was broken.
I find that if my material is grounded to 'real' earth the plasma cutter will not fire at all.
scenario:
I was cutting 3.5" pipe to make some H posts. The pipe was 21' long so I had one end on the tractor bucket (no connection to real ground as the tractor tires provide insulation) and the other on my work horse inside the workshop - it cut just fine. Next the second cut was shorter so the pipe was on the dirt outside my workshop with just one end on the work horse - no spark, nothing! I thought my plasma cutter had died. Simply lifting the end out of the dirt meant the plasma worked again. The pipe was always grounded to the plasma cutter with the ground cable.
If I put any part of my work piece on 'real' ground it will not fire. I've repeated this many times, before remembering the material must not touch the dirt. If its been hot and the dirt is dry its fine, normally though it will 'short [?]' out.

I plan to start building my water table shortly. I did not plan on 'real earth grounding' the table, just the cutter, specifically because of this discovery.

advice please . . .

[kel fab creations]

Anybody know the best/cheapest place to get some rf shielding tubing? Would aluminum foil work to see if it makes a difference before I buy the good stuff?

[MQUICK]

Have you posted this question/problem on Longevity web site? This sounds like a internal grounding problem. You may have a defect in the unit it self. Just an idea.

[kel fab creations]

Here's what I have now after another day messing with it. Plasma is grounded with 2 gage to earth, workpiece ground clamp is on earth, 2 gage from table to ground, 10 gage from comp case to earth,10 gage from controller case to earth, 10 gage from gantry to earth, and 2 gage from earth to table slats. With all that I started a program and it cut first line, moved, then the second pierce disrupted the controller again. Damn. So I spent the last couple hours wrapping wires with aluminum foil and it got worse. I wrapped the controller usb, the relay wires for the on/off, and the three wires for the three motors. Made them meet at a junction then ran a wire from that to the earth ground.
Thought I had it for a second. Did I wrap the wires wrong or do I just need real wrap?

[kel fab creations]

[kel fab creations]

Ok, so now I can start an arc manually through the driver software and manually make a cut and it doesn't interfere with anything till u get off the plate and its not cutting anything then it starts to flicker the comp monitor and the screen pointer is really delayed but it doesn't disconnect the controller. I can then turn off the arc through the driver software and everything is fine. So when I load a program and let it cut, it actually disconnects the controller on the first peirce and I have to reset it to get it to work again. Does that tell u guys anything?

[apcnc]

Connect your work lead directly to the star grnd on table. Connect the ground rod to star grnd. Connect the other grnd cables on the table to star grnd. Sheilding needs to be drained. You should have shielded cables with a drain wire connected to grnd on machine end only. Disconnect your ground cable from PC. Your ground rod may not have a good ground either. If not you can try another or go deeper. Test it. Run a 110 leg through a 100W light bulb to your ground rod. That is only using the hot leg. You are using the ground rod in place of the neutral. If it burns dim you dont have a good ground. With the bulb burning check VAC from ground rod to neutral. Should be less than 1 VAC. Try to get .5VAC. Nothing else should be connected to ground rod while checking. Be careful and use insulated clamps from bulb to grnd and on neutral. You should only have about 1A running to grnd with the resistanc of bulb but you may not like the shock.

[kel fab creations]

Alright, everything in functioning as it should now. Hurray! I took the aluminum foil off all the wires except the three motor wires. On every other wire I put a snap together ferrite choke. I probably could take the foil off the motor wires and put chokes on them too but it works as is now so I don't wanna mess with it. I really appreciate all the help u guys gave me getting it working!

Now another slight issue. I'm cutting 3/16" steel at 60 amps and the fastest I can cut is 55 ipm but the dross on the back looks like its cutting slow. This speed seems a little slow. I have the machine hooked to about a 25 ft extension of the same size coming off the machine 12AWG. Am I getting too much of a voltage drop on the extension? A calculator I found online said it would only be a 3% drop.

[kel fab creations]

Oh here's some pics of new wiring setup.