Pressure test minisplit ductless system
 

I know you have to pressure test a ductless system on install using dry nitrogen. Thing is, I have a cylinder of MIG shielding gas (Ar/CO2 mix) and was wondering if anybody used it instead of bottled nitrogen. Compressed cylinder gas spec sheets suggest that bottled N2, Ar, and CO2 all have similar moisture specs of less than 10ppm so it would seem ok. Just wondered if anybody has actually used shielding gas instead of nitrogen.
dean

Yes, that's exactly what I use when purging and leak checking units. I have a bottle of C25 gas that has found a second purpose in life besides mig welding. Works just fine. I pressurize to around 200 psi and let the rig sit for an hour after curing obvious leaks.

Just remember to draw a deep vacuum on your system afterwards. The deeper, the better. Especially if you're using R410a. It and the oil it uses both hate water. In fact, the mfr's recommend replacing the oil if it ever contacts the atmosphere. The oil absorbs water and doesn't let it go, like brake fluid.