Allied Air 4SHP13 Series Installation And Maintenance Instructions Manual page 8

Flushing Procedure
IMPORTANT: The line set and/or indoor coil must be
flushed with at least the same amount of refrigerant that
previously charged the system. Check the charge in
the flushing cylinder before flushing the unit.
1. Remove existing R-22 refrigerant using the appropriate
procedure.
If the existing outdoor unit is not equipped with shutoff
valves, or if the unit is not operational AND the existing
R-22 refrigerant will be used 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 R-22 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 new R-22 refrigerant will be used to
flush the system:
Start the existing R-22 refrigerant system in cooling mode
and close the liquid line valve. Pump all the existing R-22
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 R-410A
unit and follow the brazing connection procedure outlined
previously on this page to make line set connections.
Do not install the R-410A 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 R-410A refrigerant and may
prevent proper flushing. Use a field-provided fitting to
reconnect the lines.
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5. Remove the pressure tap valve cores from the 4SCU13
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
removed during the first flush. After each system flush,
allow the recovery machine to pull a vacuum on the
system at the end of the procedure.
9. Close the valve on the inverted R-22 cylinder and the
gauge set valves. Pump the remaining refrigerant out
of the recovery machine and turn the machine off.
10. Use nitrogen to break the vacuum on the refrigerant lines
and indoor coil before removing the recovery machine,
gauges, and R-22 refrigerant drum. Re-install pressure tap
valve cores into the 4SCU13 unit's service valves.
11. Install the factory-supplied fixed orifice (or thermal
expansion valve approved for use with R-410A
refrigerant) in the liquid line at the indoor coil.
Refrigerant Metering Device
4SCU13 units are designed for use with either fixed orifice
or TXV systems. Refer to the appropriate following section
for information on installing the chosen refrigerant metering
device.
Fixed Orifice Systems
4SCU13 units are shipped with a fixed orifice refrigerant
metering device. See specification sheets for the proper
fixed orifice size for each unit. In nonstandard applications,
the fixed orifice provided with the indoor unit may not be
Issue 0921 506272-01