Workpiece Grounding

[henrym]

Now I will eventually be TIG welding with a non-contact HF arc starting unit, and I'd like to avoid any trouble that I can. grounding the workpiece apparently reduces the probability of an electrical mishap, and is recommended...?

I would rather not connect to the main house ground (connected to plumbing) because perhaps any stray current could find its way back to any tools and computers on that ground, and maybe relatives using the sink?!


so I think having a separate ground connection would be a good idea. say a battery clamp on a 10-12 AWG cable connected to a rod in the ground outside the garage?


BTW: Ground as in GND. not the work clamp connection in the welding circuit:

http://http://www.millerwelds.com/ed...cles6.html


this topic seems somewhat vague.
anyone else do this? what do you use?

[rlitman]

I've never had a problem, except for a tiny amount of TV snow.
AND, I'm not so sure that having a separate ground rod is allowed in the NEC. It sure seems like a bad idea, which leaves open the possibility of dangerous ground loops.

If you are worried about interference, it would be best to beef up your "ground system".
All of your grounds (house, etc), should meet at one point, by your main panel.
Your house "should" have two grounds. One connected to your water pipe (if it is copper), and a ground rod connected here as well.
If you don't have a ground rod for your house (just trace the bare copper wire from your main panel to the water pipe, and see if it goes anywhere else), then installing one would be a priority.

The important thing here, is that if your house's grounding system has a good enough path to ground, you will not get stray voltages at your sinks, etc. Actually, having a better path to ground, also improves the performance of surge protection equipment as well.

So, from there, if you want a good ground at your workbench, I would run a #6 (or maybe # green or bare wire from the point that your grounds meet up, to a terminal block near your welder, and then connect from there to the ground screw on your welder, and your workbench. That should be more than adequate.

If you MUST have a ground rod right at your workbench (this would be the ultimate in reducing interference, but shouldn't be necessary at all), I would bond it to your building's ground (at the same point where everything meets up), with a minimum of #4 wire. That bond needs to be able to withstand a lightning strike.

[vault]

I'm not so sure that having a separate ground rod is allowed in the NEC.

you are right it is not.

[KHK]

henrym
Check out the drawings below, especialy the third one.
We constantly interchange the ground and neutral terms.
You must have two hot wires and a neutral wire run all the way to the welder for 240 volt wireing.
All wires must be the same size.
From the Miller link that you provided they are talking about grounding the work table I think??

keith

[henrym]

to clarify, the welder is wired up already (240v) and has been used for stick welding quite a few times.
(thanks for the drawing regardless!)

at the moment I'm just unsure about grounding the workpiece. what should it be grounded to?

so far, I have not grounded any workpieces and I don't have a steel table.


rlitman,
are you saying that while the positive output terminal (work clamp) is of course connected to workpiece, the workpiece shall also connected to the house's ground that is also connected to the welder's chassis?

I previously just thought it seems odd to effectively connect a live work-lead to the welder's grounded chassis... and I would prefer not to experiment with such things!


thanks

[Gadget]

Henrym
If I understand what you are saying, you want to know if the piece to be welded should be grounded. If you are welding DCEN (DC Electrode negative) the workpiece is connected by the ground wire which is actually positive. If you were to also ground the workpiece to an earth ground you would effectively short circuit the welder, not a good thing. I weld things all the time that are not setting on a metal table, the only ground you need to connect is the welder ground cable.
The ground wire most of the discussions above refer to is a ground lug on the back of the welder, not the workpiece.
Dan

[henrym]

If you are welding DCEN (DC Electrode negative) the workpiece is connected by the ground wire which is actually positive. If you were to also ground the workpiece to an earth ground you would effectively short circuit the welder, not a good thing. I weld things all the time that are not setting on a metal table, the only ground you need to connect is the welder ground cable.
Dan

I know that the terms are always confused, so let's get this straight.


Ground connection: GRND. earth or ground as in a line actually connected to the earth/ground. NOT the Work Clamp.


Work lead/clamp: the work cable/lead and clamp connected to the welder's DC + output terminal and clamped to the workpiece in DCEN welding applications, DC- for DCEP.
work lead and clamp regardless for AC.


Electrode/Stinger/Torch lead: duh.


So, the question was: should the workpiece be grounded, and to what? if I was using a steel table, the workpiece and table would be the same electrical part.

the welder's chassis is already connected to the house's ground line through the third wire in the power cord.

some people seem to recommend grounding the workpiece to the main ground that everything else is connected to on top of connecting the work lead, apparently reducing "zapping/shock issues" and I thought that to be wrong, since that would be effectively connecting a welding lead to the welder's chassis and home plumbing... so I asked the question that is the first post.


again, ground is GRND. work lead is work lead and electrode is electrode, as specified in the first post!

[henrym]

from the miller link I posted:

The workpiece being welded and the frame or chassis of all electrically powered machines must be connected to a good electrical ground. This can be accomplished by connecting it to a properly grounded building frame or other appropriate ground. Chains, wire ropes, cranes, hoists and elevators must never be used as grounding connectors.

The work lead is not the grounding lead. The work lead connects the work terminal on the power source to the workpiece. A separate lead is required to ground the workpiece or power source.

[Gadget]

I guess all I can say is I have NEVER connected an earth ground to the workpiece and have not had any problems. I worked in production line welding for about a year many years ago and none of that work was grounded to an earth ground. So, I wouldn't bother with a separate ground.
Dan

[KHK]

Yes I agree with Gadget.

Afew years ago I burned up a grinder cord when my steel work bench was un-grounded. The welding power went through the grinder's power cord to ground. This was with a buzbox welder. Lucky for me The grinder was OK, just the cord was smoked.

keith