I do not have a 211I but that is informative. My Thermal arc 250 GTS. would not work with +20 degree temps. It is 2000 vintage so I chalked it up to early stage inverter quirks. This is something that I have not taken into account in the past. I will in the future. The -4 degrees for the MTS250 is livable +14 on that 211 would not be. I will say that neither will replace my miller extreme suitcase feeder in the near future that I can see. I had hoped that an inverter in a pelican case type setup could replace it but the temp limits would be a killer here in the north. There are times when you have to work in sub zero temps although I try not to. Anything that can not be used at least down to zero F would be a no go for sure and -10 would be better. The push controls on the MTS are not a good idea in cold climates either. Everytime I push one I am thinking the plastic membrain over the top of them is going to crack. So far they have not. Even for regular use in warmer weather I am not thrilled with them. I have to take my glove off in order to have enough feel to work the buttons.