RSL 

Refrigerant Solutions Limited 

 

Appendix 9 

RS-50 (R442A)

RETROFIT PROCEDURE TO REPLACE R22 

Replacing R22 with RS-50 essentially will follow the procedure specified by the 

equipment manufacturer for a refrigerant change. Since RS-50 is zeotropic it is very 

important that liquid, not vapour, refrigerant be added to the system. 

1. Ensure the right equipment is available, eg recovery unit and cylinders, container for 

recovered lubricant, vacuum pump, weighing scales, replacement drier etc. 

2. Before removing the R22, operate the unit under standard operating conditions and 

record the pressures, temperatures and any other relevant measurable data to establish 

unit performance. Typically, the appropriate standard conditions for setting up the 

unit will have already been specified by the equipment supplier. 

3. Recover and weigh the R22 from the unit. The weight should be within the range 

specified by equipment manufacturer. 

4. If mineral oil or alkylbenzene are being used in the system, which is common in the 

case of R22, it is necessary to change the lubricant to a miscible lubricant such as a 

polyol ester. It is advisable to check with the compressor manufacturer which type 

and viscosity of lubricant to use. The remaining amount of mineral oil or 

alkylbenzene left in the system should be less than 5%. 

5. Record the quantity of oil removed from the system, and compare with the amount 

recommended by the compressor manufacturer, since this is the quantity of lubricant 

that will need to be replaced. 

6. Recharge the same quantity as in 5 above with a suitable miscible lubricant. 

7. Since the mass flow of R442A is similar to R22, it will not be necessary to change or 

adjust the expansion device. 

8. Replace the filter/drier and evacuate the system. 

9. Before operating the unit, charge the unit with liquid RS-50. The weight added at this 

stage should be approximately 10% lower than the R22 charge specified by the 

equipment manufacturer. 
 RSL 

 Refrigerant Solutions Ltd 

2 

 

10. Operate the unit under conditions similar to those used in Step 2. Although 

compressor suction pressures will be similar to those experienced using R22, 

discharge pressures will be approximately 20% higher which may require the higher 

pressure cut out to be reset and controls to be adjusted accordingly. It is important 

that the operating limits of the compressor etc are not exceeded. 

11. Check superheat to ensure the system is operating satisfactorily. 

12. Check system thoroughly for leaks. 

13. Remove all R22 labels and clearly label system RS-50. 

RS SERIES OF REFRIGERANTS PRESSURE/TEMPERATURE CHARTS 

RS Series Pressure/Temperature charts indicate both liquid bubble point and vapour dew 

point of the RS Series Refrigerant. 

Liquid Bubble Point: this is the temperature which the liquid refrigerant will begin to 

vaporize at the given pressure. Below this temperature the liquid refrigerant will be subcooled. 

Vapour Dew Point: this is the temperature at which refrigerant vapour will begin to 

condense at the given pressure. Above this temperature the refrigerant vapour will be 

superheated. 

EvaporatorVapour Superheat:

To determine evaporator superheat, measure the suction line temperature at the outlet 

pipe of the evaporator and measure the suction pressure at the outlet pipe of the 

evaporator. Using the Pressure/Temperature chart, determine the vapour dew point for 

the measured suction pressure. Subtract the determined dew point from the actual 

temperature and this difference is the evaporator superheat. 

Condenser Liquid Sub-Cooling:

To determine condenser sub-cooling, measure the temperature of the outlet pipe of the 

condenser and measure the condenser pressure at the outlet pipe of the condenser. Using 

the Pressure/Temperature chart, determine the liquid bubble point for the measured 

condenser pressure. Subtract the measured temperature from the determined bubble point 

and this difference is the condenser liquid sub-cooling.