Welding Tips and Tricks

My shop is kinda small, so in an effort to use my space more efficiently, I stretched my little welding cart vertically to accommodate both welders. One is a 240vac ac/dc inverter TIG, the other a 120vac MIG (transformer based I assume).
As I was finally installing both machines on my newly improved cart, I found myself instinctively clamping the ground clamps for both onto the frame of the cart. This made me think.. (I do this more often than I probably should). What happens if one machine is running DCEN and the other positive.. do bad things happen to either machine if the clamps are both connected to the same place? Or worse.. perhaps there are some more subtle unintended electrical consequences to having two units with different power supplies in physical contact with each other.

Do I have any real cause to be worried?

Welcome aboard!

As long as both machines are wired correctly and your shop is wired to code (any code in the last 40 years or so), you have no issues. Each machine will see the "ground" or workpiece terminal at the same potential. EP, EN, and AC are all relative to that ground. We commonly have a MIG or two, a TIG, and Plasma cutter grounded to the same workpiece, and sometimes all three are being used simultaneously.

Steve S

bcrawford wrote:My shop is kinda small, so in an effort to use my space more efficiently, I stretched my little welding cart vertically to accommodate both welders. One is a 240vac ac/dc inverter TIG, the other a 120vac MIG (transformer based I assume).
As I was finally installing both machines on my newly improved cart, I found myself instinctively clamping the ground clamps for both onto the frame of the cart. This made me think.. (I do this more often than I probably should). What happens if one machine is running DCEN and the other positive.. do bad things happen to either machine if the clamps are both connected to the same place? Or worse.. perhaps there are some more subtle unintended electrical consequences to having two units with different power supplies in physical contact with each other.

Do I have any real cause to be worried?

In sort nothing will happen as they are different electrical circuts.

For safety, transformer machines are isolated from utility so that line(s), neutral and ground are not shared with either the electrode or work. Nothing like an autotransformer or Variac.

Inverter machines are the same. In fact they also use transformers only instead of being heavy 60Hz things, they run at thousands of cycles making them much smaller.

bcrawford wrote:My shop is kinda small, so in an effort to use my space more efficiently, I stretched my little welding cart vertically to accommodate both welders. One is a 240vac ac/dc inverter TIG, the other a 120vac MIG (transformer based I assume).
As I was finally installing both machines on my newly improved cart, I found myself instinctively clamping the ground clamps for both onto the frame of the cart. This made me think.. (I do this more often than I probably should). What happens if one machine is running DCEN and the other positive.. do bad things happen to either machine if the clamps are both connected to the same place? Or worse.. perhaps there are some more subtle unintended electrical consequences to having two units with different power supplies in physical contact with each other.

Do I have any real cause to be worried?

Welcome to the forum. My friend bought a Miller 350 Mig from a guy for peanuts that was brand new but it didn't work. He sent it in for repairs and was told that some circuit was fried because it had gotten jolted by having another machine grounded to the same table it was and somehow induced with current. They said that the gun had been laid on the table with wire sticking out and that provided the path. I don't know if I believe that but I suppose it could happen somehow. I always make sure to disconnect a machine from the table if I am running another machine just to be safe. They aren't cheap to get fixed and I'm sure stranger things have happened.