Allied 4SCU18LT Series, Installation And Maintenance Instructions Manual

Page: 8 / 25

Flushing Existing Line Set and Indoor Coil
This procedure should not be performed on systems
which contain contaminants, such as compressor burn
out.
Required Euipment
The following equipment is needed to flush the existing line
set and indoor coil (See Figure 9). Two clean R-22 recovery
bottles, an oil-less recovery machine with a “pump down”
feature, and two sets of gauges (one for use with R-22 and
one for use with R410A).
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 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.
Figure 9
506254-01 Page 8 of 25 Issue 0912