Lennies914 is in the field welding on a large CoGeneration system and is having problems with the welder. The system is built into a building and wired into the electrical system. The welder is pluged into the wall and the CoGen unit is shut off.

When the welder ground is attached to the CoGen unit and he attempt to weld the wire heats up inside the feeder and the wire melts and balls up! If he disconnects the ground the wire feeds fine. I used this welder a week ago and it worked great at my house!

The question is:

What would cause this? Would the fact that the CoGen system is grounded to the same plug that the welder is pluged into cause a problem? If a battery is hooked to the CoGen system would that cause this problem? OR Is there anything else that may cause this problem?

Probably ground looping. Lennie has my number

Thats what I told him it could be! I am just looking for a comfirmation!

The inside of a wire feeder is isolated from the outside world.

The internal mechanism with the feed wheels must not be electrically connected to the wire feeder housing because the entire mechanism is at the same potential as the weld wire.

Something inside the feeder must have shorted to the housing.

Try setting the feeder up on a piece of plastic and try it again.

If the wire melts the same way, then the short is inside the welder power supply part.

HTH

Stu

There are + and - wires inside the flip up door that are held on by wing nuts. one of them sits right next to the feeding mechanism. Maybe one came loose.

BTW.. thats a good little unit, I have the same welder, works great. I just recently converted it to MIG and it welds stainless great.

Thanks Guys,

I just got home and tried my welder. It works fine. So I will try again Monday to make my repair on the cogen unit. At the time I was thinking the problem was in my welder but now I need to look at other options. I guess I should open the main breaker on the generator to start with, and maybe disconnect the battery (good idea regardless). I was attempting to weld on the exhaust with the ground clamped to the exhaust manifold. When I pulled the trigger (not welding, just feeding wire) the wire started glowing at the feed wheels.
Any other thoughts or an explanation?

I converted mine also. Did you change the wire to weld stainless?

Is the welder sitting on the Co Gen unit? There may be a short inside the welder that only faults when the welder housing (outer case) touches the same piece of metal (the Co Gen unit) as the wire.

The welder is sitting on a cart that is on rubber wheels!

Lennie, maybe the cart was touching the motor or something that was grounded to the engine??

Are you using a power recepticle from the Co Gen? The groung of the AC power is bonded to the chassis ground on most Gens. Perhaps the ground loop. Is your unit a 120V system? If so, the ground and neutral on the recepticle should also be bonded at the source, adding to the ground loop problem.

It was on the cart, away from the unit. I'm sure there is a logical explanation. I just don't want to have to remove the parts if they can be welded in place.

I was hoping you'd chime in Mike. I was using a wall recep. Although the cogen does supply power to the building it has to be running and the contactor closed.

That was my first explanation when Lennie called me! I don't know how he could seperate it from the ground! Maybe you will have to remove all of the ground wires including the CoGen power ground!

Check the liner. The liner could be contacting a ground source within the welder. The liner is acting as your ground source back to the feed roller. Make sure there is no slag inside the nozzle and make sure the welder end of the liner is not grounded.

Are you running this on 110?

Thanks Rick! I think we have eliminated a problem with the welder! Lennie tested it when he got home today and it works fine at his house!

It has to be a ground loop coming from the CoGen unit to the circut breaker ground panel!! Even if the breaker is turned off the ground is a constant and as kg6dxn said the neutral may also be looped in the system through the CoGen 120v generator!

Cool, That's a strange one. Good luck with it.

Bonding the Neutral to the ground is an NEC (National Electrical Code) standard in the US. This is at the Main service panel at you home or buisness. They are also bonded at every transformer. It is possible they are bonded in the welder too.

So, if the recepticle on the Co Gen is either: 1. Wired out of phase... or 2. "floating 120V" (60V +/- on each wire. Standard power in Operating rooms for example) it could F up the welder operation. I think Lennie should bring a long extension cord and fing another recepticle.

BTW... Floating 120V is used in operating rooms so that the "hot" leg only searches for the neutral leg and NOT to earth ground. This is done so the patients that are being worked on are not electricuted if a power tool shorts out during surgery.

I didn't read all the answers above, but my first inclination would be to replace the gun.

Yep! got some .030 stainless wire to weld some exhaust parts, worked great. You will need tri mix gas for stainless....it's not cheap.