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c. Thermometer on Suction Line = 59°F.
To obtain the degrees temperature of superheat, subtract 50.0 from
59.0°F. The difference is 9° Superheat. The 9° Superheat would fall
in the ± range of allowable superheat.
CHECKING SUBCOOLING
Refrigerant liquid is considered subcooled when its temperature
is lower than the saturation temperature corresponding to
its pressure. The degree of subcooling equals the degrees of
temperature decrease below the saturation temperature at the
existing pressure.
1. Attach an accurate thermometer or preferably a
thermocouple type temperature tester to the liquid line
close to the pressure switch.
2. Install a high side pressure gauge on the liquid access
fitting.
3. Record the gauge pressure and the temperature of the
line.
4. Compare the hi-pressure reading to the "Required Liquid
Line Temperature" chart. Find the hi-pressure value on
the left column. Follow that line right to the column under
the design subcooling value. Where the two intersect
is the required liquid line temperature. Alternately you
can convert the liquid line pressure gauge reading to
temperature by finding the gauge reading in Temperature
- Pressure Chart and reading to the left, find the
temperature in the °F. Column.
5. The difference between the thermometer reading and
pressure to temperature conversion is the amount of
subcooling.
Subcooling Formula = Sat. Liquid Temp. - Liquid Line Temp.
EXAMPLE:
a. Liquid Line Pressure = 417
b. Corresponding Temp. °F. = 120°
c. Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling, subtract 109°F from 120°F.
The difference is 11° subcooling. See the specification sheet
or technical information manual for the design subcooling range
for your unit. See R-410A Pressure vs. Temperature chart.
Cooling Refrigerant Charging (5 Ton Models)
Check unit charge before putting the cooling section into full
operation. The 5 Ton Models have a thermostatic expansion
valve metering device. To ensure the unit is properly charged for
the intended application, check the unit refrigerant sub-cooling
at the condenser. The refrigerant sub-cooling is a function
of outdoor ambient temperature and return air temperature
of the conditioned space. It is the installing contractors
responsibility to ensure the proper refrigerant sub-cooling at
the condenser is adjusted for each application. As the outdoor
ambient temperature rises the sub-cooling decreases and
as the outdoor ambient temperature lowers, the sub-cooling
increases. NOTE: Proper sub-cooling adjustment optimizes
cooling performance. Models equipped with thermostatic
expansion valve, charge the system to sub-cooling, range
shown on chart, when necessary, adjust expansion valve stem
for superheat setting.
Superheat Adjustment (5 Ton Models)
To adjust superheat, remove the control box cover and locate
the expansion valve on the liquid line of the evaporator.
Unscrew the cover from the expansion valve, locate the
adjustment screw, and turn it clockwise (in) to increase
superheat or counterclockwise (out) to decrease superheat.
Replace adjustment cap. Wait a minimum of 10 minutes
between adjustments to allow time for the TXV and pressures
to stabilize.
NOTE: The expansion valve will not need adjustment for most
applications. Ensure system superheat is set within range listed on
chart.
Cooling Operation
NOTE: Mechanical cooling cannot be reliably provided at ambient
temperatures below 50° F.
1. Turn on the electrical power supply to the unit.
2. Place the room thermostat selector switch in the COOL
position (or AUTO if available, and if automatic changeover
from cooling to heating is desired).
3. Set the room thermostat to the desired temperature.
TROUBLESHOOTING
Ignition Control Error Codes
The following presents probable causes of questionable
unit operation. Refer to Diagnostic Indicator Chart for an
interpretation of the signal and to this section for an explanation.
Remove the control box access panel and note the number of
diagnostic LED flashes. Refer to Diagnostic Indicator Chart
for an interpretation of the signal and to this section for an
explanation.
Fault Recall (Two-Stage Models ONLY)
The ignition control is equipped with a momentary push-button
switch that can be used to display on the diagnostic LED the
last five faults detected by the control. The control must be
in Standby Mode (no thermostat inputs) to use the feature.
Depress the push-button switch for approximately 2 seconds.
NOTE: Do not hold for longer than 4 seconds. Holding
the button for 4 seconds or higher will erase the memory!
Release the switch when the LED is turned off. The diagnostic
LED will then display the flash codes associated with the last
five detected faults. The order of display is the most recent fault
to the least recent fault.
Abnormal Operation - Heating
Internal Control Failure
If the integrated ignition control in this unit encounters an internal
fault, it will go into a "hard" lockout and turn off the diagnostic
LED. If diagnostic LED indicates an internal fault, check power
supply to unit for proper voltage, check all fuses, circuit breakers
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