Welding cable in conduit for use as welding lead

Status
Not open for further replies.
O

Off_Grid

Member
Location
California
Occupation
Electrician
Hi,
I'm trying to improve an existing situation & need some input.

Current situation: A single welder located on the ground floor, with a "permanent" welding lead strung up and knot-tied to handrails of multiple expanded metal catwalks approximately 100' up a wood fired boiler structure, to achieve "convenient access" to welding points on upper levels, by disconnecting the cable sections at the floor needed to connect a stinger whip lead. -Not great.

The project goal: Install 1" conduit up the structure, with 4 T 1.5" condolets for remote welder lead receptacle stations, and a short removable lead to the welder that can be plugged in when needed for upper level welding. a single wire will be run & daisy chained to all remote stations with a split bolt & pigtail to the receptacle inside each station.

The question I need some input on, is the wire itself. I was advised that it would be a bad idea to run welding lead in conduit in this application, though it couldn't be explained why. I have tried researching it with little result in this application. This will be used primarily for maintenance and repair work, not all day everyday service. Would it be acceptable in this application, since we already have the cable on hand, or should I run something different?
 
One possibility is, that welding cable is not listed as building wire so installing it in conduit might be considered permanent wiring. You might check with your AHJ as to whether or not your proposal will pass.
 
A small problem-
As mentioned, welding cable usually isn't listed as building wire, use THHN in the conduit and panel-mount terminals instead of running fine-strand cable.

A much larger problem-
With metallic conduit, and expecially steel, if the welding uses AC instead of DC and you run a single lead, and the grounded conduit will form a choke around the electrode lead and really mess up the current available (this is why single grounding conductors are bonded to the enclosing conduit). I'm assuming that the welders use the building steel as the return/workpiece conductor.
 
zbang said:
A small problem-
As mentioned, welding cable usually isn't listed as building wire, use THHN in the conduit and panel-mount terminals instead of running fine-strand cable.

A much larger problem-
With metallic conduit, and expecially steel, if the welding uses AC instead of DC and you run a single lead, and the grounded conduit will form a choke around the electrode lead and really mess up the current available (this is why single grounding conductors are bonded to the enclosing conduit). I'm assuming that the welders use the building steel as the return/workpiece conductor.
Click to expand...

You would be correct about the return conductor. Good to know about the choke effect, I hadn't thought of that.....
 
Maybe run a 2 lead system so they can 'ground' their work closer to the workpiece? Or leave as-is. Or use aluminum conduit. For the wire you could use DLO/RHW but the insulation is kind of thick. You can also get regular RHW with class K stranding but that is usually special order but something Anixter might have as its used heavily in telecom. THWN would be cheapest/easiest but I think you might have trouble landing it on the welding connectors. Instead of the T conduit body and trying to tap the large conductor in there, why not put bigger pullboxes between each section of conduit and panel mount the welder connector to the box?
 
Todd0x1 said:
Maybe run a 2 lead system so they can 'ground' their work closer to the workpiece? Or leave as-is. Or use aluminum conduit. For the wire you could use DLO/RHW but the insulation is kind of thick. You can also get regular RHW with class K stranding but that is usually special order but something Anixter might have as its used heavily in telecom. THWN would be cheapest/easiest but I think you might have trouble landing it on the welding connectors. Instead of the T conduit body and trying to tap the large conductor in there, why not put bigger pullboxes between each section of conduit and panel mount the welder connector to the box?
Click to expand...

What I have actually done for the receptacles, was a short section of 1-1/4" conduit off the sides of the T's, going to handrail mounted 8" Hoffman A808CH enclosures, each with the receptacle mounted in the door, and weatherproof spring shut covers. The plan being to make the connections inside those enclosures with flexible weld cable (or similar) pigtails to the receptacles.
 
A little update:
The welder being used is an old Lincoln Idealarc R3R-300, DC output only.

What are the thoughts on using THHN in the conduit as a welding lead? I know the fine stranded cable carries current differently, Comparing RHW to THHN actually looks like it would handle more current in the same gauge as THHN, with a better thermal rating as well, & the bonus of a pulling jacket. The overall run will be around 120-130' long.
 
For DC, it doesn't matter much. Nor do the NEC tables since in reality this probably doesn't fall under the NEC anyway (there isn't much about welding secondary cables), and welders have a low duty cycle. I would prominently mark the entire thing for "DC welding only" because sometime in the future someone is sure to try AC.
 
Status
Not open for further replies.
Top