Welder Ground Lead

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infinity

infinity

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This is a common on new construction buildings where the welders are all connected to a panel in an area and they only run one lead to the location where they're welding. The other lead goes to the nearest electrical conduit, metal strut, and anything else that's connected to the building electrical system. We recently had a problem with a large MC feeder that was arcing against some EMT due to this. How dangerous is this practice of grounding one side of the welder to electrical raceways?

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infinity said:
...We recently had a problem with a large MC feeder that was arcing against some EMT due to this. How dangerous is this practice of grounding one side of the welder to electrical raceways?
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Can you provide more information has to how this feeder arcing was determined to be "due to" the welders? I've never heard of that, and I've been welding for 30 years and am a long-time contributing member of the welding forums for Miller and Hobart.

The oldest dinosaur machines out there typically have an open-circuit voltage of less than 70 V. Voltage during welding is typically in the 20s.

I've put my work lead against more EMT that I can remember.

Interesting tangent perhaps: It's not really a "ground lead" as it's part of the current path, and can be any polarity, depending on the process.

EDIT: I now think you mean the exterior metal armor of a large MC cable was arcing against some EMT. Yes, this could be possible if that became the short circuit of the welding current flowing along the raceway. Sounds rare, but possible. Did it put a hole in the armor?
 
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MAC702 said:
EDIT: I now think you mean the exterior metal armor of a large MC cable was arcing against some EMT. Yes, this could be possible if that became the short circuit of the welding current flowing along the raceway. Sounds rare, but possible. Did it put a hole in the armor?
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That's what was happening and it was determined that they had connected the lead directly to the metal armor of the MC cable. The armor had a burn spot but hadn't made a hole yet. The contact was intermittent and only occurred if someone pushed the MC cable against the EMT.
 
IMHO it is an NEC violation to use either a wire or a raceway EGC as the current return path on either the primary or the secondary side of the welding transformer.
It is 100% objectionable current in either case. I am sure that it is contrary to the use instructions of the welding equipment too.
It does not make any difference that this is a temporary setup during construction.
As a practical rather than code issue, using building steel for the entire return would be less hazardous than using an EGC as part of the path. Still illegal though.
And, as previously mentioned, part of the encouragement for this violation is erroneously thinking of the welding lead as a "ground" rather than a grounded current carrying conductor.
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One would think that with this setup, using the building electrical system as part of the welder circuit would yield lousy results.
 
infinity said:
One would think that with this setup, using the building electrical system as part of the welder circuit would yield lousy results.
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Using metallic conduit near the welding machine is often the most (and sometimes the only) convenient way to clamp onto the building's common bonded steel structure, needing only the electrode lead (stinger or wirefeeder) to be strung to the other part of the structure that you are welding something to.

I've never seen the work lead clamped onto MC though, and would not think it appropriate, but EMT wouldn't give me a second thought, right or wrong. :huh:
 
MAC702 said:
Using metallic conduit near the welding machine is often the most (and sometimes the only) convenient way to clamp onto the building's common bonded steel structure, needing only the electrode lead (stinger or wirefeeder) to be strung to the other part of the structure that you are welding something to.

I've never seen the work lead clamped onto MC though, and would not think it appropriate, but EMT wouldn't give me a second thought, right or wrong. :huh:
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This is in an all concrete high rise building with no structural steel. The welding is for gas piping, supply and return chilled water, etc.
 
infinity said:
This is a common on new construction buildings where the welders are all connected to a panel in an area and they only run one lead to the location where they're welding. The other lead goes to the nearest electrical conduit, metal strut, and anything else that's connected to the building electrical system. We recently had a problem with a large MC feeder that was arcing against some EMT due to this. How dangerous is this practice of grounding one side of the welder to electrical raceways?
Click to expand...

You're nicer than I am, I wouldn't let them clamp to conduits/cables, or electrical specific strut racks, etc.

They can clamp onto another trades pipework if they want, but electrical would be off limits for me.

They could always drag a big ground lead from the welder to the area they are working in and all the welders ground clamps could tap off that.
 
infinity said:
This is in an all concrete high rise building with no structural steel. The welding is for gas piping, supply and return chilled water, etc.
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I'd still use an EMT run for my work lead if it ran through, assuming the EMT supports and other pipe supports are all bonded as I'd expect anything metallic in the building to be, and I didn't have a way to connect to my weldment pipe at the machine. Looks like it is common to do so there, too, but I will repeat that I'd have certainly avoided a spiral-wrapped MC cable for my connection, but perhaps being an electrician gives me more insight on that. It's also possible all weldors would think of that, but the apprentice sent to the first floor to "hook up the lead to the electrical conduit" wouldn't.

Are they using the common support methods at the top floor or are they using another double-clamped lead at the top from the EMT to their other pipe?

This has been a good question, and I'm wondering if I might see things sometimes that would have me avoid it.

Most of the time that I've clamped to conduit was when I was working on billboards and it was the only real thing at the bottom of the sign that the clamp would fit on. The only thing I pulled up to the top of the sign was a stinger lead. Mine was also the only crew on the sign at the time.
 
Cow said:
...They could always drag a big ground lead from the welder to the area they are working in and all the welders ground clamps could tap off that.
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Each weldor is almost always working from an independent power source, with different settings, perhaps even different processes with different polarities.

I will say that while a building is under construction, I wouldn't hesitate to avoid any electrical conduit if the electricians had a problem with it.
 
Cow said:
...They could always drag a big ground lead from the welder to the area they are working in and all the welders ground clamps could tap off that.
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As an edit to my earlier thought: Yes, this principle would work, with a common lead that was tapped on both ends, if big enough (though welders will usually not bother to wonder about the ampacity of metallic tubing).

It would also require this common lead to go everywhere, just like other metallic components of the building already do, or be easily moved and extended, and would only be feasible if the weldors spend enough time in each position to make it worth it, and are on a common crew to be sharing something.

So, yes, but they'd really consider it a pain in the ass.

BUT, if the electricians are on site, and object, I really don't see how they can protest having to find another way. Hopefully there are other nonobjectionable metallic things nearby.
 
so the clamps in the pic are secondary clamps?? is it a TIG machine?
if so they might likely be there in case the work piece primary clamp falls off during welding.

According to American National Standards Institute (ANSI) Z49.1, "Safety in Welding, Cutting and Allied Processes," the workpiece or the metal table that the workpiece rests on must be grounded. You must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent of or separate from the welding circuit connection.

Some welding machines use starting and stabilizing circuits that contain high-frequency voltage. This is common on gas tungsten arc welding (GTAW) machines. The high-frequency voltage may have frequency components that are in the megahertz range. In contrast, the welding voltage may be as low as 60 Hz.
High-frequency signals tend to radiate away from the welding area. These signals may cause interference with nearby radio and television reception or other electrical equipment. One way to minimize high-frequency signal radiation is to ground the welding circuit. The welding machine instruction manual includes specific instructions on how to ground the welding circuit and components in the surrounding area to minimize the radiation effect.
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so when you clamp your workpiece you essentially have clamped to the egc. std practice, and i dont think this caused any issue for any wiring.
 
I have only worked with smaller MIG and TIG welders in non-building-construction applications. But in those applications I regard it as extremely stupid to ground the work table and run the welder return lead to some remote grounded object. The return lead should be placed on the work, as close as practical to the welding location. Grounding the work or work table may also be a good idea, but not if it ends up being part of the return. Perhaps I'm missing something about other types of welding applications.
 
FionaZuppa said:
so the clamps in the pic are secondary clamps?? is it a TIG machine?
if so they might likely be there in case the work piece primary clamp falls off during welding.



so when you clamp your workpiece you essentially have clamped to the egc. std practice, and i dont think this caused any issue for any wiring.
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" the workpiece or the metal table that the workpiece rests on must be grounded. You must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent of or separate from the welding circuit connection.
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To me that clearly says not to use the ground connection as the welder return lead!
The OP is describing a situation in which the workpiece does not have a welding circuit connection (other than through the EGC).
Note, however, that it does say "should" rather than "must".
 
GoldDigger said:
To me that clearly says not to use the ground connection as the welder return lead!...
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No, it's basically saying that in addition to your electrode lead and your work lead clamp, you ALSO make sure your weldment is grounded. It's a completely separate issue. In this type of situation, though, it's automatic because the grounding is also the work connection. It won't always be.
 
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