ground rod question

[jkeyser14]

I recently picked up a tig welder w/ an input of 100 amps at 240v full load. Miller's instructions for the unit say that the welder's working ground should be attached to the panel ground as well as directly to a ground rod.

The welder is in an attached garage w/ it's own sub panel. I was under the impression that you only want a ground rod at the main panel, and that you never drive another ground rod at the sub panel because you can create multiple ground paths. I know I've read in the NEC book somewhere that manufacturer's instructions can trump code, but this welder is 40 years old and a lot has changed over those years.

 

[sberry]

Is this an attached garage? Any separate buildings need a rod but as for the welder don't worry about it. It needs to be connected to the buildings electrical system like any other appliance, ground wire to the panel.

 

[jdieter]

OK another ground rod for a sub-panel in a detached building, how is the sub-panel bonding done. Is the neutral bus bonded to the sub-panel tub and where does the ground wire from the ground rod attach, the neutral bar or the bonding bar?
When I was doing wiring many years ago, the code was to carry a seperate neutral and bond wire to any sub-panel and not bond the neutral regardless of the physical location of the sub-panel relative to the main disconnect grounding.

 

[jkeyser14]

The sub panel ground and neutral aren't bonded. The reason I'm asking about the ground rod at the sub panel / garage can be summed up pretty well in this thread:

http://www.millerwelds.com/resources/communities/mboard/showthread.php?t=17041

My manual for the welder says that all wiring within 50 feet of the wire should be shielded or in grounded metal conduit, and the welder's work ground needs to be attached to a ground rod as well as the panel ground.

 

[sberry]

My manual for the welder says that all wiring within 50 feet of the wire should be shielded or in grounded metal conduit, and the welder's work ground needs to be attached to a ground rod as well as the panel ground.

The welders work ground shouldn't be tied to the electric system, where did you read that? My benches are grounded so by default its tied but I took great care not to have building and electric wires baconer an alternate pathway for welding currents. I know they do call for shielded wiring in the vicinity of the unit but its very rarely done, most of mine is piped, a few fixture cords but I don't have interference issues so WTF. Most home systems are not run like a bat out of hell, several hours a day, run it, see if there is any problems.

 

[jkeyser14]

The welders work ground shouldn't be tied to the electric system, where did you read that? My benches are grounded so by default its tied but I took great care not to have building and electric wires baconer an alternate pathway for welding currents. I know they do call for shielded wiring in the vicinity of the unit but its very rarely done, most of mine is piped, a few fixture cords but I don't have interference issues so WTF. Most home systems are not run like a bat out of hell, several hours a day, run it, see if there is any problems.

It's called out in the owner's manual of my welder on page 42 of 62:
http://www.millerwelds.com/om/o340p_mil.pdf

 

[Charles (in GA)]

It's called out in the owner's manual of my welder on page 42 of 62:
http://www.millerwelds.com/om/o340p_mil.pdf

The sole purpose of which is, as the manual says, to prevent re-radiation. They are telling you this so the FCC will not come after them for causing interference with electronics, radios, TVs, etc. As Sberry noted, try it, if you experience interference (wife says the TV went crazy while you were out in the shop, or neighbors start complaining) then do something about it, otherwise, drive on.

The illustration shows a ground rod dedicated to the welder chassis and work ground. It is not intended to be part of the electrical system of the building, but is connected to the secondary of the welder.

Charles