grounding welding benches

[Sberry]

I have the welding bench grounded to the building frame thru a 1/2 rebar about 10 ft long. I use it for plasma cutting and occasionally for light stick welding. The cutter and welder grounded to the link to reduce cables. I have 120V recepts on the benches. I insulated the grounding and try not to weld with any 3 prong equipment sitting on the benches where a welding current could find an alternate back thru the green wire. For years I depended on the steel to be the only grounding means but that really doesnt go with the same cable or raceway,,, although they are under the floor in proximity. I was thinking the way to go might be to feed the table might be from a gfci source with only 2 wire? I know it will clear a fault to the steel, but how safe is it in terms of responce time? Maybe the best thing would be to just unhook the electric ground wire and use the building steel for that circuit? Actually now that I think about it I have 2 benches linked by imbeds to the building with 2 circuits coming from 2 different panels going to them. Come to find out I have another 3 wire circuit that feeds the chop saw sitting on the same bench. Maybe gfci circuits would be best.

[Old Man Stick]

Im not sure what your trying ask here. Maybe its becouse I have been smelling Gas fumes all day? ( *&$^ gas tanks in the truck! ) But if your worried about the ground of your electrical on your welding table? I have two 4 outlet boxes bolted right to my welding table. I have never had a problem. My bench is 4'X 16' half of it has a top on it for doing other work. the other half is all open for welding. I have a 8" bench grinder that boldet right to the same bench top. Been that way for atlest 3 years now. I dont have a Plasma cutter Yet But I have miged, stick, and tryed to tig ( still cant do that for the life of me!) and have not had a problem.

OMS

[cope]

Sberry, why did you ground the welding bench?

[Sberry]

It reduces leads on the floor with a welder ground going to the bench under the floor. The problem comes that if any 3 wire electrical equipment is connected to this bench that the equipment grounding wire could possibly become an alternate path for the welding current. If your bench wasnt bonded to the building steel it wouldnt matter. In my case I am using imbeds and building steel for grounding these benches for welding current. Does that make any more sense?

[Sberry]

I forgot, I tig weld thru that ground too.

[cope]

Originally posted by Sberry27
It reduces leads on the floor with a welder ground going to the bench under the floor. The problem comes that if any 3 wire electrical equipment is connected to this bench that the equipment grounding wire could possibly become an alternate path for the welding current. If your bench wasnt bonded to the building steel it wouldnt matter. In my case I am using imbeds and building steel for grounding these benches for welding current. Does that make any more sense?

Not really, but I guess that grounded tools could be an issue even if you didn't have a direct ground, since the steel comes in contact with both the floor and possibly steel walls. I try to keep my electric tools away from my welding anyway.

[Franz]

Somebody is sniffin some bad argon here, cause I can't find a problem in the original question.
A GFCI responds in milliseconds, so if there is a ground fault, the GFCI will trip quicker than spit on hot iron evaporates.
My benches are all gridded together, and have 3 wire plugs on them, and it has never been a problem.
The only possible problem would occurr when the electrical ground to the tools and the grounding grid on the welding benches are at different resistance to ground, but that would be eliminated by tieing the electrical ground to the bench itself.
Metering ground resistance differences requires special metering equipment, but it can show some very interesting results.

[Sberry]

I think the gfci might be the thing,, what I am trying to do is eleminate the possibility of a ground wire becoming a welding ground. It would turn a 12 or 14 wire hot in a couple seconds.

[bjdenommee]

My shop bench is also grounded to the machine by cable, and not to a earth groung per say, and I have never had aproblem with grinders, drill and what such.

I tig mig, stick and plasma cut on and around it and my power supplies are not mounted to the bench but the wall above it.

you got me to think now about grounding, never say it in any book but I will look into it for sure

Thanks
Bernie

[bjdenommee]

Here is a pic of my setup

[Guest]

My bench is grounded to the machine through a 2" wide x .050" stainless flat bar. It eliminates the cable on the floor under your feet...the problem with it, is that when i use 200 plus amps, it expands and comes right up off the floor about an inch! I like it, because I can roll stuff over it, and it doesn't interfere with the sweeping. I like the rebar in the floor idea...may do that, too.

BTW the only time you will have a problem with the 120v outlets on a weld bench is when you forget to ground your machine.

[Sberry]

Yes. I think I am going to cut a new raceway for a conduit that follows the rebar and put all the circuits feeding these benches in that. I actually have power to there from the main panel and a subpanel and thats not good either. It should be from the main panel only and I could use that imbed connecting rod as the equipment grounding conductor directly back to the panel. Its just like that strap you have. Mine ends up right below my electric source which is where the welders sit.

[UncleDannie]

There is nothing wrong with your original plan. My shop is set up the same way. A 4'X8'X1/2" sheet of steel with six legs. The welder is grounded to the building and the table is attached by 1/4 steel plate, 4" wide. I have four 4-plex outlet boxes, one at each corner. I added a short (3 foot) gronding cable with clamp at one end of the table in case I have to weld sometnig on the floor, so I'll have a ground for that. If I was going to go the route with a gfi plug, I'd just buy a GFI Breaker Switch and install it in the breaker box to cover the circuit. A little more expensive, but a lot quicker to do.

[Sberry]

Yes, I have a jumper lead with a ground clamp on it on the bench for remote work too. I used a lead connector so I can add or remove leads. I also have a lead and ground from a colum that reaches out the door and goes to a stick welder. Its nice to be set to reach outside thru a big side door and zap stuff without pulling inside. In the summer daylight is so nice to work in sometimes. I will get a camera soon and post some pics

[DaveD]

Just a thought. I'm not sure the National Electric Code is going to be happy with some of these grounding ideas. Any industrial NEC experts out there?

Here is something weird that happened to me a few years ago. Had a steel table grounded real well. Had a 100 foot extension cord (3 wire properly grounded) wrapped on a neat metal spool and had the 3 prong grounded outlet mounted directly on the spool. It kept the extension cord neat and I only had to unreel what I needed. Only had about 10' unwound and was running a metal cased router on the table. My arms were resting on the table and I got this tingling sensation in my arms where they brushed up against the table. Well it so happens the cord wrapped on the metal reel made it a transformer and put about 80 volts on the ground wire and router case without blowing any breaker. As I unwound the cord from the reel I could watch the voltage go down on the ground wire. Needless to say I threw the nice steel reel away. I think the only thing that saved my butt was the amperage must have been very low.