Page 8
Issue 0912 506253-01
(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
4SCU16LT 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 R22 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 R22 refrigerant drum. Re-install pressure tap
valve cores into the 4SCU16LT unit’s service valves.
11.
Install a thermal expansion valve approved for use with
R410A refrigerant
in the liquid line at the indoor coil.
Refrigerant Metering Device
4SCU16LT units are designed for use with TXV systems only.
Expansion valves equipped with Chatleff-type fittings are
available from the manufacturer. See Table 3 for proper
TXV for each unit.
To install an expansion valve (see Figure 9):
1. Separate the distributor assembly and remove the
piston orifice and used teflon seal. Insert nozzle end of
the expansion valve along with a new teflon seal into the
distributor and tighten to 20 – 30 ft. lbs. Use backup
wrench on all wrench flats.
Overtightening will crush
the teflon seal and may cause a leak.
2. Attach liquid line portion of distributor assembly along
with new teflon seal to the inlet of the expansion
valve. Tighten to 20 – 30 ft. lbs. Use backup wrench
on all wrench flats.
Overtightening will crush the
teflon seal and may cause a leak.
3. Connect the external equalizer line to the equalizer
port on the suction line and tighten to 8 ft. lbs.
4. Strap the superheat sensing bulb to the suction header.
If installing an expansion valve on an indoor coil that
previously used a fixed orifice, be sure to remove the
existing fixed orifice. Failure to remove a fixed orifice
when installing an expansion valve to the indoor coil will
result in improper operation and damage to the system.
Table 3
TXV Data
l
e
d
o
M
r
e
b
m
u
N
t
r
a
P
6
3
-
,
4
2
-
T
L
6
1
U
C
S
4
1
0
V
X
T
4
A
T
L
6
1
U
C
S
4
8
4
-
2
0
V
X
T
4
A
T
L
6
1
U
C
S
4
0
6
-
3
0
V
X
T
4
H
