Parker's HVACR Tech tips cover service tips for the HVACR technician servicing commercial refrigeration systems as well as HVAC for both commercial and home. The following are service tips for working with blended refrigerants.
Refrigerant charging with R-400 or R-500 series refrigerants
Good service practices dictate that only liquid should be removed from the cylinder. The proper cylinder position for liquid refrigerant removal is indicated by arrows on the cylinder and/or cylinder box. Once liquid refrigerant is removed from the cylinder, the refrigerant can be charged into the system as a liquid or vapor as desired. Use gauge manifold or a throttling valve to flash the liquid to vapor if required.
The mixing of refrigerants
Do Not mix refrigerants with different “R” numbers. Uncertain safety criteria, performance and/or system damage could result.
Which refrigerants can be used without changing lubricant type (drop-in)?
Newer HFC blends and HFO blends are compatible with POE oil, so there is no need to change oil types if retrofitting from an HFC such as R404A to R407A, R407C, R448A, or R449A. The same is true of retrofits from R134a to R450A or R513A. If an existing HCFC system (such as R22 with mineral oil) is being retrofitted it will be necessary to change oil type to POE.
In situations where it is not necessary to change oil types, it is still good practice to drain as much existing oil from the system as possible, and refill with new oil. This will help to remove contamination from the system.
Refer to the OEM system or compressor manufacturer's guidelines for the proper lubricant. If this information is not available, you can refer to lubricant recommendations published by the refrigerant and oil suppliers.
Fractionation within the blended refrigerant, has it taken place in your system?
Fractionation: A change in composition of a blend by preferential evaporation of the more volatile component or condensation of the less volatile component. When servicing a system containing a blended refrigerant it is necessary to confirm that the existing refrigerant has not fractionated, therefore producing less capacity.
General Rule of Thumb around Fractionation
Under saturated static conditions a: 10% loss in pressure = 5% loss in capacity
Net glide of various R400 series refrigerants at 40°F saturated suction:
R407A has 10ºF glide, 26% more capacity than R404A
R407C has 11°F glide, same capacity as R22
R410A has almost no glide, same capacity as R22
R448A has 10°F glide, 30% ,more capacity than R404A
R513A has no glide, 16% less capacity than R134a
HVACR Tech Tip Article contributed by John Withouse, Senior Engineer Refrigeration, Sporlan Division of Parker Hannifin
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