Multiple welders

[BigBand]

I'm tired of moving around two welding carts with tanks, and all my welding tools when I need a differrent welder, so I'm making a multiple tool welding cart. It will hold my MIG and my TIG welders, a tank of Argon and a tank or Stargon, and will have drawers for clamps, accessories, etc.
My plan is to have an electrical receptacle in the back that everything will plug into, and then just have one 220 V plug to go to the wall.

Now, here is the question: Can I get away with having a common ground electrode for the whole shebang? Seems like I could, assuming (I know, I know) the individual ground clamps from the MIG and TIG actually go directly to the ground from the electrical mains.

[Mondo]

First: That clamp you afix to the work piece isn't a ground clamp. It is a work clamp. And it isn't common to Earth Ground. It could very well have some other potential on it in reference to Earth Ground. This is especially true of mobile welding machines, but should be considered even for shop machines that are powered from a building panel.

Next: If you connect the two work clamps to a common piece of metal and then run a cable from there to your actual work piece your idea will work, but I certainly would not feel comfortable with that arrangement. I would feel far safer to simply use which ever clamp and cable I needed for the machine I was using at the present. That is not to say if you are done using one and want to change to the other you must disconnect the first one first. Leave 'em both connected. The point is you should not have welding current from one machine flowing through any portion of the aparatus of the other machine, and this includes the work electrode cable. Each machine should entirely support it's own welding current circuit. The dangers are overcurrent in the work cable or damage to the either or both machines.

-Mondo

[jotram]

hes right its not a ground clamp .....its a work clamp....

[Fat Bastard]

Originally Posted by Mondo

First: That clamp you afix to the work piece isn't a ground clamp. It is a work clamp. And it isn't common to Earth Ground. It could very well have some other potential on it in reference to Earth Ground. This is especially true of mobile welding machines, but should be considered even for shop machines that are powered from a building panel.

Next: If you connect the two work clamps to a common piece of metal and then run a cable from there to your actual work piece your idea will work, but I certainly would not feel comfortable with that arrangement. I would feel far safer to simply use which ever clamp and cable I needed for the machine I was using at the present. That is not to say if you are done using one and want to change to the other you must disconnect the first one first. Leave 'em both connected. The point is you should not have welding current from one machine flowing through any portion of the aparatus of the other machine, and this includes the work electrode cable. Each machine should entirely support it's own welding current circuit. The dangers are overcurrent in the work cable or damage to the either or both machines.

-Mondo

Just a thought here.

Two welders working on the same pipe both machine work lead clamped to the same pipe stand. How is this different from the OP hooking both work leads to common lead (all of sufficient size) and then taking that lead to the work?

TJ

[BigBand]

Originally Posted by Mondo

If you connect the two work clamps to a common piece of metal and then run a cable from there to your actual work piece your idea will work,

OK, that's actually how I was going to do it. Sorry, I wasn't very clear.

That is not to say if you are done using one and want to change to the other you must disconnect the first one first. Leave 'em both connected.

Isn't this the same thing ?

[Mondo]

Originally Posted by Fat Bastard

Just a thought here.

Two welders working on the same pipe both machine work lead clamped to the same pipe stand. How is this different from the OP hooking both work leads to common lead (all of sufficient size) and then taking that lead to the work?

TJ

The difference is with two machines clamped to same work each machine supports its own electrical circuit. Machine-to-stinger-to-clamp-to-machine. However, if two machines are clamped to a common lead then the common lead takes the current for both machines, at least to the point where they share the connection. The combined current may exceed the "ampacity" of the common lead. In this situation not only is the common lead in danger of failure, the electricity (electrical flow to be specific) starts seeking other paths and will follow "the path of least resistance." There is danger here for the weldor as well as the machines.

I confess I am not a weldor with many years experience. I am an electronics technician with many years of experience and training. I know it is common practice to have numerous welding machines clamped to the same work, such as in a pipeline or a steel structure. In most instances this works satisfactorily as the "work piece" being a large pipeline or steel structure (boat, bridge, office tower, etc) and has ample metal to carry the current load of each machine back to that same machine. But to combine machine loads onto a single copper cable is an invitation for disaster. Even if it were a one-man shop and he used only one machine at a time, the concept still smells like trouble in river city.

I suppose if the work lead for each of two machines was say AWG 2 and the common lead was 4/0 then this might be safe, if you can gain clean and secure enough electrical connections, especially the clamp-to-work interface. But who has an ample length of 4/0 on hand? Or wants to invest in the cost and then drag it around or coil it up when done working?

-Mondo

[Static-XJ]

Originally Posted by Mondo

The difference is with two machines clamped to same work each machine supports its own electrical circuit. Machine-to-stinger-to-clamp-to-machine. However, if two machines are clamped to a common lead then the common lead takes the current for both machines, at least to the point where they share the connection. The combined current may exceed the "ampacity" of the common lead. In this situation not only is the common lead in danger of failure, the electricity (electrical flow to be specific) starts seeking other paths and will follow "the path of least resistance." There is danger here for the weldor as well as the machines.

I confess I am not a weldor with many years experience. I am an electronics technician with many years of experience and training. I know it is common practice to have numerous welding machines clamped to the same work, such as in a pipeline or a steel structure. In most instances this works satisfactorily as the "work piece" being a large pipeline or steel structure (boat, bridge, office tower, etc) and has ample metal to carry the current load of each machine back to that same machine. But to combine machine loads onto a single copper cable is an invitation for disaster. Even if it were a one-man shop and he used only one machine at a time, the concept still smells like trouble in river city.

I suppose if the work lead for each of two machines was say AWG 2 and the common lead was 4/0 then this might be safe, if you can gain clean and secure enough electrical connections, especially the clamp-to-work interface. But who has an ample length of 4/0 on hand? Or wants to invest in the cost and then drag it around or coil it up when done working?

-Mondo

Anywhere I use "ground", I am talking about the work lead of the welding circuit, not earth ground, chassis ground, or any other type of ground.

Using one welder at a time through a common work lead is no big deal. You need to complete the circuit to pass current, so only the machine in use is passing any current through the work lead. If the work lead is capable of carrying the max current that can be supplied by either machine, over the required distance, then it'll be fine. If you plan on having a buddy over and the two of you using both machines at the same time, the common cable will need to be capable of carrying the max combined current of both machines over the required distance.

I routinely did something similar at work. The cell I used to work in had a Miller Deltaweld 652 with Miller D64M feeder, a Lincoln SquareWave Tig 355, and an 80 am plasma cutter. Each machine has their own work lead and clamp. There was a rotary positioned hard grounded into the Deltaweld. I generally left the work clamps from all three machines clamped to the work table. About 75% of the work I did was with parts in the gripper chuck on the positioner. I never moved work clamps to the positioner, when working off the positioner the tig and plasma cutter passed their current (when in use) back up the work clamp on the Deltaweld, then onto positioner. There were no ill effects because of this setup.

[BigBand]

I am a one man shop, and will only have one of the welders turned on at a time.

[Fat Bastard]

Originally Posted by Mondo

The difference is with two machines clamped to same work each machine supports its own electrical circuit. Machine-to-stinger-to-clamp-to-machine. However, if two machines are clamped to a common lead then the common lead takes the current for both machines, at least to the point where they share the connection. The combined current may exceed the "ampacity" of the common lead. In this situation not only is the common lead in danger of failure, the electricity (electrical flow to be specific) starts seeking other paths and will follow "the path of least resistance." There is danger here for the weldor as well as the machines.

I confess I am not a weldor with many years experience. I am an electronics technician with many years of experience and training. I know it is common practice to have numerous welding machines clamped to the same work, such as in a pipeline or a steel structure. In most instances this works satisfactorily as the "work piece" being a large pipeline or steel structure (boat, bridge, office tower, etc) and has ample metal to carry the current load of each machine back to that same machine. But to combine machine loads onto a single copper cable is an invitation for disaster. Even if it were a one-man shop and he used only one machine at a time, the concept still smells like trouble in river city.

I suppose if the work lead for each of two machines was say AWG 2 and the common lead was 4/0 then this might be safe, if you can gain clean and secure enough electrical connections, especially the clamp-to-work interface. But who has an ample length of 4/0 on hand? Or wants to invest in the cost and then drag it around or coil it up when done working?

-Mondo

Mondo Your thinking is reasonable and follows logic, to a point. It falls a part at the highlighted areas. In my experience the the overwhelming majority of the time the weakest link in the circuit is not the cable it is the connection of the cable to the work clamp and or the work clamp to thew work.


To the op I can see no reason for you not to do this. I have had several setup's just like what you describe.

At the union between the tow machine and the single work lead I would use as short a cable as is practical. I would use a "lug" bolted connection (see photo) . and the size of the single common work lead can be the same size ("0" "00" ...)as the you have been using. The only read danger is if both machines are in use at the same time and out amping the system. At that point the likely result would be the work clamp getting vary hot and melting.

I have melted my share of work clamps and cable connectors all due to loose connections (loose equals resistance equals heat equals something melting. As long as the weak link is not at the machine I see no issues.

[Mondo]

I have seen lengths of wire literally burn up in other types of circuits where demand exceeded the ampacity of the wire while the connetors survived nicely, getting hot only from the heat of the burning wire. When the ampacity of a circuit conductor or the current handling capacity of a circuit is exceeded trouble brews and right quickly too. If one connects the work clamp circuit of two 100 Amp machines to a single common work lead then that common lead, and any connectors from the point of interconnection to and including the clamp, should be rated 200 Amps for safety.

-Mondo

[Fat Bastard]

Originally Posted by Mondo;239728[I

]I have seen lengths of wire literally burn up in other types of circuits where demand exceeded the ampacity of the wire while the connetors survived nicely[/i], getting hot only from the heat of the burning wire. When the ampacity of a circuit conductor or the current handling capacity of a circuit is exceeded trouble brews and right quickly too. If one connects the work clamp circuit of two 100 Amp machines to a single common work lead then that common lead, and any connectors from the point of interconnection to and including the clamp, should be rated 200 Amps for safety.

-Mondo

Then the circuit was wired with under sized leads. If the capacity had been increased to 200A then all would have been well? Thus no burning wires.

My point being if the OP intends on using only 1 machine at a time (as using both would pose difficulties for a single operator) then wiring the circuit with cable sized to meet the needs of the larger (amps) of his machines then he has no worries. If he adds a second operator then the wire size would need to be sized accordingly.

More over . The point is you should not have welding current from one machine flowing through any portion of the aparatus of the other machine, and this includes the work electrode cable. Each machine should entirely support it's own welding current circuit. The dangers are overcurrent in the work cable or damage to the either or both machines.

-Mondo I don't see any danger of current flowing from one machine through the other to complete a welding circuit. If this were the case you would never see multiple welders welding on the same weldment simultaneously. Each welder (electric powered machine not engine driven) has two major circuits the infeed power supplied via the grid or genset and the welding circuit, they don't mix.


So as I stated earlier "Two welders working on the same pipe both machine work lead clamped to the same pipe stand. How is this different from the OP hooking both work leads to common lead (all of sufficient size) and then taking that lead to the work?

TJ " Size matters.

[farmersamm]

This is a great conversation. I'm not sure I fully understand it, but that's my problem

I never thought about it before, but I've seen pictures of shipbuilding yards where a lot of machines are working at the same time. There must be a reason the machines don't fry each other. Y'al may already have explained it, and I didn't catch on yet.

Does it have anything to do with the proximity of your work cable to other machines working down the line?

I'm confused as hell

[Mondo]

It is common to have multiple machines on one "work piece" such as when constructing ships, buildings, pipelines, bridges, etc. That isn't the problem. Under most conditions the machines will not impact each other. BigBand can certainly do what he proposes. I was only warning about possible overcurrent on the work lead causing problems.

My point being only that if two machines use a common lead it needs to be sized to handle the current that will be demanded of it. So if BB sets this up with a common lead he can't use both machines at once so it doesn't matter, as long as the lead is no smaller than the fattest from either machine.

Until he has a pal over and they are both working on opposite ends of the same project. If the common lead is not sized accordingly there will be problems, and not just overcurrent damage to the leads.

Electricity can be seemingly fickle. When a circuit conductor is inadequate to support the demand, but the demand is still there, the over current condition causes something to heat up or get burned up. I am sure we have all seen this happen, or at least evidence of it. It is what we may not see but manifests in damage somewhere else. When the demand for electron flow exceeds the capacity of the circuit the electrical current will seek other paths, not just burn up the inadequate conductor. Although welding machines are generally designed and constructed to be well isolated from the currents of other devices on the welding side of the circuitry, I do not believe that isolation is absolute for all possible conditions. I certainly would not want to risk two machines that cost me several hundred bucks or more each by relying on an inadequate common work lead. So like FB said in his last post: Size matters.

I will say no more.

-Mondo

[BigBand]

Gentlemen - thanks to you both. Your concern for my safety and the safety of my equipment (and my wallet) is appreciated!

I will insure that I only use one machine at a time.
.

[Static-XJ]

Originally Posted by Mondo

My point being only that if two machines use a common lead it needs to be sized to handle the current that will be demanded of it. So if BB sets this up with a common lead he can't use both machines at once so it doesn't matter, as long as the lead is no smaller than the fattest from either machine.

Until he has a pal over and they are both working on opposite ends of the same project. If the common lead is not sized accordingly there will be problems, and not just overcurrent damage to the leads.

Agreed 100%.

[BTD]

I'm in the same situation as BigBand. I have three machines (MIG, TIG and Plasma) on one cart. Power supply will be a common plug to the wall outlet. (I even have the drawers BigBand mentioned.)

I would also like to have a common work lead and understand that the common work lead must be sized for the total current assuming multible machines operating at the same time (although I doubt this will ever be the case).

My question is, if I have all three work leads connected to a common lead and that common lead falls off the work piece (or I forget to connect it), will I damage the machines. For instance, if I'm using the MIG and the nozzle of the idle plasma is resting on the work piece and the common work piece lead isn't connected will the current flow thru the idle plasma cutter and cause damage. I suppose this would be the same situation if I forgot to connect the MIG work piece clamp but left the plasma clamp attached (and the plasma nozzle is resting on the work) then tried to use the MIG.

From a housekeeping standpoint, I really like the idea of one cable instead of three but I REALLY don't want to fry several thousand dollars worth of machines.

[Brink]

One work lead big enough to satisfy the largest machine (which you should already have) with twist-lock connectors on all.

Like this:

[BTD]

Simple, foolproof, inexpensive...thanks Brink.