Pressure test minisplit ductless system

[MrV]

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

 

[jad3675]

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

I used Argon when I pressure tested mine. I think you'll be OK using the Ar/Co2 mix.

John

 

[bazar01]

Nitrogen purging also keeps the inside of the copper tube clean and free of oxidized layer during brazing in open air that can flake off from the brazed section and block the metering device.

I don't see any issue since Ar/CO2 is a welding shielding gas and will keep the atmospheric air and moisture from infiltrating the system and you will pull a vacuum anyway after pressure testing as long as you have the necessary fitting adapter to connect to the unit service valves. If the unit is pre-charged, just make sure the sevice valves are tightly closed.
Somebody else with more experience might have a different opinion.

 

[malibu101]

When I work on automotive A/C systems I use 100% argon since I have have it for aluminum MIG. As well I have 75/25 MIG mix also but have not used it in an A/C system although I don't see why you couldn't. As long as the gas is dry, clean, and free of oxygen I think it would be OK but again I don't know for a fact.
I have no use for 100% nitrogen as I don't do enough A/C work to warrant another cylinder and the argon has worked fine for me many times.

 

[PWC Repair]

One of my contractors uses CO2. There should be no welding on a mini-split system as most manufacturer specs call for all flared fittings. The flaking from the welds is the reason. Those systems are VERY particular about even the tinyest of particles screwing up a 500 position electronic TXV. The most important thing will be a very good vacuum before cracking open the valves. I would guess it calls for less than 500 microns.

 

[LS6 Tommy]

Shouldn't use CO2. It has a high moisture content. That's why you're supposed to use dehydrated nitrogen...

Tommy

 

[Jackfre]

I have seen a lot of problems with mini-splits that have the line set silver soldered. Especially on those 1/4" lines. Only a drop of solder either partially or completely blocks the refrigerant flow. Better, as the manuf specify, that they be properly flared.

 

[MrV]

Thanks for the replies.
dean

 

[PWC Repair]

Shouldn't use CO2. It has a high moisture content. That's why you're supposed to use dehydrated nitrogen...

Tommy

Wrong CO2, I'm talking about bone dry CO2 that used to be used long before the practice of dry nitrogen. I'm guessing your CO2 for welding would be bone dry but I'm not positive. You get about 3 times the amount in the same size bottle as compared to nitrogen.