Non-noncondensables


First let’s talk about what a noncondensable gas is. 

Any gas that does not condense (change from vapor to liquid) under the normal compression refrigeration conditions is called a noncondensable gas or NCG. These would commonly be air, nitrogen, carbon dioxide, Argon and Oxygen.

Noncondensable is the system will result in high head / condensing temperature and occasionally high side pressure fluctuations as well as decreased cooling capacity and efficiency.

The only way to remove non-condensibles reliably is to recover the entire charge and recharge with virgin refrigerant. You can’t remove noncondensables with a line drier and while you do remove air with a vacuum pump you only remove the air that entered the system once you open it. The vaccuum does nothing for the refrigerant the already pumped down or recovered as the non-condensables remain mixed with the refrigerant unless you are dealing with large volumes where they can actually be separated and the NCG’s removed.

However….

Noncondensables is often a term used by techs to mean ANYTHING in the refrigerant that shouldn’t be there, such as moisture, solid contaminants and other refrigerants.

Carbon buildup from brazing is a solid contaminant, not a noncondensable. Moisture in the system is moisture in the system, not a noncondensable. A mixed refrigerant (such as R410a) charged in vapor instead of liquid is a fractionated charge…. not noncondensables

I think you get the point

–Bryan

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