# 504,910M
Page 5
If the existing outdoor unit is not equipped with shutoff
valves, or if the unit is not operational AND you plan to
use the
existing
R22 refrigerant to flush the system:
Disconnect all power to the existing outdoor unit.
Connect the existing unit, a clean recovery cylinder, and
the recovery machine according to the instructions
provided with the recovery machine. Remove all R22
refrigerant from the existing system. Refer to the
gauges after shutdown to confirm that the entire system
is completely void of refrigerant. Disconnect the liquid
and suction lines from the existing outdoor unit.
If the existing outdoor unit is equipped with manual
shutoff valves AND you plan to use
new
R22 refriger-
ant 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 sys-
tem. Disconnect the liquid and vapor lines from the
existing outdoor unit.
2. Remove the existing outdoor unit. Set the new R410A
unit and follow the brazing connection procedure (see
page 6) to make line set connections.
Do not install
the fixed orifice or R410A thermo expansion valve
at this time.
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.
3. Remove the existing refrigerant flow control orifice or
thermal expansion valve before continuing with
flushing procedures. The existing devices are not
approved for use with R410A refrigerant and may
prevent proper flushing. Use a field-provided fitting to
reconnect the lines.
4. Remove the pressure tap valve cores from the
SCU12M unit’s service valves. Connect an R22
cylinder with clean refrigerant to the suction service
valve. Connect the R22 gauge set to the liquid line
valve and connect a recovery machine with an empty
recovery tank to the gauge set.
5. 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.
Figure 3
Flushing Connections
Note: The inverted R22 cylinder must contain
at least the same amount of refrigerant
as was recovered from the existing
system.
