By now, CFCs such as R12, R502, and R11 and the main HCFC, R22, have been banned from new unitary and commercial HVAC&R equipment due to ozone depletion concerns. These refrigerants have been replaced - for the time being at least - by HFCs such as R410A, R134a, and R407C. In making this transition, the industry has had to address many issues with HFCs concerning reliability, safety, and performance. This article deals with major cleanliness issues when manufacturing equipment using HFCs.

Process Fluids

Using any HFC refrigerant such as R134a, R407C, or R410A means it is necessary, due to solubility concerns, to use polyester (POE) lubricants in the compressor instead of the mineral oils used for decades with HCFCs and CFCs. It is important to note that many process fluids used in the manufacture of compressor components, coils, tubing, and other parts, which were not incompatible with mineral oils can be damaging to a system using POEs. Refrigerant/lubricant Solubility characteristics can be altered. More importantly, carbonaceous
matter can precipitate within the lubricant and, as it circulates through the system, it will deposit within the expansion device. When the expansion device becomes restricted during field operation, it becomes necessary to make costly service repairs. It is imperative that (1) all vendors supply refrigeration components completely clean and free of process fluids and (2) that process fluids used in the assembly of components be removed before the system is evacuated and charged.

Moisture

Water can be more damaging to an HFC/POE system than the usual HCFC/mineral oil system, although it is undesirable in all systems. The fact that synthetic POE is manufactured with complex acids and water means water can tend to reverse the process, leading to chemical breakdown of the system. It is therefore highly recommended that all HFC systems contain a drier from a reputable supplier.

Minimum water removal capacity for a system drier should be 1.2 drops per lb. refrigerant in the system. A system with 10 pounds of refrigerant should have a minimum water removal capacity of 12 drops. Note: Drier manufacturers rate their products in drops at 60 ppm end point dryness. There are 20 drops per gram of water.

Editor's Note: CR4 would like to thank Dick Cawley of GEA Consulting for contributing this blog entry.