115amps is realistically suited to 2-2.5mm really...anything too thick will suck the heat out of the puddle and you will get a cold weld that won't penetrate too farWhat about 3mm-4mm?
What size rods at what setting?
The 'standard' generic "150A" boxes are much of a muchness - 3-4 rods anywhere near full power reducing as the dust builds up...
5mm, with reasonable duty cycle...probably 180+ Amps
150 might just do it, but will be constantly kicking in the overheat after a few minutes welding..
I agree of course but experience and testing have taught me a thing or two.When welding 5mm plate I use about 140amps (hard to tell on the R Tech equipment) and by bevelling(rooting) I get very good integrity and penetration. When welding 12mm plate I start at the root,achieve a good deep puddle and then do a criss cross motion over that after which I go back to the root and repeat the procedure keeping the heat going.So you have had success. I'll start with what I agree with which is the prep and method does need to be right to stand a chance but I don't agree 180 amp unit is going to give proper side wall fusion on a 12mm plate. Your root run fair enough it's up to it as a small root face can be penetrated into with dip transfer but after that you need power to ensure adequate fusion of the side walls and inter runs. Design Usually takes over when success is achieved using under powered equipment by way of taking the stress off the welds and onto the structure itself.
I also don't agree that short circuit (dip) transfer is suitable for welding 5mm plate. Again root run or thinner materials yes but 5mm shouldn't need rooting a light prep at the most then straight down it in spray IMO. Welding underpowered particularly with GMAW will eventually bite you in the bum come the day structure design can't help you out.