Flushing Connections

Note: The inverted R22 cylinder must contain at least the same amount of refrigerant as was recovered from the existing system.

Figure 8

If the existing outdoor unit is equipped with manual shutoff valves AND new R22 refrigerant will be used to flush the system:

Start the existing R22 refrigerant system in cooling mode and close the liquid line valve. Pump all the existing R22 refrigerant back into the outdoor unit.

(It may be necessary to bypass the low pressure switches to ensure complete refrigerant evacuation.)

When the low side system pressures reach 0 psig, close the suction line valve. Disconnect all power to the existing outdoor unit. Refer to the gauges after shutdown to confirm that the valves are not allowing refrigerant to flow back into the low side of the system. Disconnect the liquid and suction lines from the existing outdoor unit.

2.Remove the existing outdoor unit. Set the new R410A unit and follow the brazing connection procedure outlined previously on this page to make line set connections. Do not install the R410A thermal expansion valve at this time.

3.Make low voltage and line voltage connections to the new outdoor unit. Do not turn on power to the unit or open the outdoor unit service valves at this time.

4.Remove the existing R-22 refrigerant flow control orifice or thermal expansion valve before continuing with flushing procedures. R-22 flow control devices

are not approved for use with R410A refrigerant and may prevent proper flushing. Use a field-provided fitting to reconnect the lines.

5.Remove the pressure tap valve cores from the 4HP16LT unit’s service valves. Connect an R-22 cylinder with clean refrigerant to the suction service valve. Connect the R-22 gauge set to the liquid line valve and connect a recovery machine with an empty recovery tank to the gauge set.

6.Set the recovery machine for liquid recovery and start the recovery machine. Open the gauge set valves to allow the recovery machine to pull a vacuum on the existing system line set and indoor coil.

7.Invert the cylinder of clean R-22 and open its valve to allow liquid refrigerant to flow into the system through the suction line valve. Allow the refrigerant to pass from the cylinder and through the line set and the indoor coil before it enters the recovery machine.

8.After all of the liquid refrigerant has been recovered, switch the recovery machine to vapor recovery so that all of the R-22 vapor is recovered. Allow the recovery machine to pull a vacuum on the system.

NOTE: A single system flush should remove all of the mineral oil from the existing refrigerant lines and indoor coil. A second flushing may be done (using clean refrigerant) if insufficient amounts of mineral oil were

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Issue 1004

506468-01