19
M
INI
-S
PACE
EC I
NSTALLATION
, O
PERATION
AND
M
AINTENANCE
M
ANUAL
2. Disconnect the refrigerant cylinder from the discharge
side of the compressor and connect it to the suction side.
3. Refer to “3.0 Start-Up/Commissioning” on page 22.
Start the A/C system and use the system controller to
lower the room temperature setpoint 3-5 °F below actual
room temperature, thus ensuring cooling remains on as
the unit is charged.
4. When
fi ne tuning the charge on cool days it may be nec-
essary to restrict the airfl ow across the condenser coil to
raise the pressure. The fan closest to the header must be
running. When fi ne tuning the charge, ensure the pres-
sures are correct for the type of refrigerant used. Refer
to the tables in section 2.11.1, “Pressure/Temperature
Settings” for the operating temperature and pressure
ranges for R410A refrigerant.
5. Block off a portion of the intake air to the condenser until
a constant discharge pressure can be obtained. This will
lower the possibility of overcharging. Allow the discharge
pressure to rise to 445-480 psig and hold it constant.
6. Slowly meter liquid refrigerant through the suction side
while watching the pressure gauges and monitoring
superheat and sub-cooling temperatures.
CAUTION
Add liquid refrigerant slowly to prevent the refrigerant
oil from “washing out” of the compressor.
7. Take a superheat temperature reading near the feeler
bulb from the controller with the temperature measur-
ing device being well insulated. The ideal superheat
temperature is 12-15 °F. Maximum allowable superheat
temperature is 20 °F.
CAUTION
Do not exceed 20 °F superheat. Exceeding this
temperature may cause the compressor to fail.
8. While monitoring the pressure, take a sub-cooling tem-
perature reading on the output side of the condenser. The
sub-cooling temperature should be 10
–
20 °F.
9. If necessary, (slowly) add liquid refrigerant to the suc-
tion side until the correct sub-cooling temperature is
achieved.
CAUTION
Remove the blockage from the air intake of the
condenser.
10. Fill out the applicable sections of the Warranty Regis-
tration and Start-Up Checklist.
2.9.4.4
-30 °F Ambient Applications
NOTE
For units designed for -30 °F operation, a receiver
is used to store the refrigerant during the time the
condenser is not using the extra refrigerant charge.
1. Follow steps 1-9 in section 2.9.4.3, “Refrigerant Charg-
ing Procedure” . Once superheat and sub-cooling tem-
peratures are stabilized, additional refrigerant must be
added to the receiver.
NOTE
It is important not to exceed 80% of the total
condenser and receiver volume to allow room for
expansion.
2. A refrigerant level sight glass is located on the side of
the receiver to assist the service technician in charging
the air conditioning system. The proper charge can be
determined by viewing the level of refrigerant in the re-
ceiver while the unit is running at an elevated discharge
pressure.
3. Keep the air intake to the condenser blocked and
maintain the discharge pressure at 445 psig and hold
it constant. The condenser fan nearest the condenser
header should be operating continuously. All other fans,
if additional fans exist, should be off during this time.
4. Add additional refrigerant charge to the receiver as
needed until the refrigerant level rises to the center of the
sight glass, indicating the receiver is 80% fi lled.
When the refrigerant in the receiver reaches the sight
glass, the unit is fully charged.
CAUTION
Remove the blockage to the air intake of the
condenser.
5. Fill out the applicable sections of the Warranty
Registration and Start-Up Checklist.
2.10 System Settings and Adjustments
2.10.1 Low/High Pressure Limit Switch
Air conditioning systems utilizing thermal expansion valves
are equipped with hermetically sealed high-pressure and
low-pressure switches. These switches are preset by the
manufacturer and cannot be adjusted. The high-pressure
switch opens at 630 psig and has a manual reset. The low-
pressure switch opens at 65 psig (± 10) and closes at 105
psig (± 10) and has an automatic reset.
