18
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.
SUPERHEAT
Checking Superheat
Refrigerant gas is considered superheated whenever its
temperature is higher than the saturation temperature
corresponding to its pressure. The degree of superheat
equals the degrees of temperature increase above
the saturation temperature at existing pressure. See
Temperature - Pressure Chart.
1. Run system at least 10 minutes to allow pressure to
stabilize.
2. Temporarily install thermometer on suction (large) line
near compressor with adequate contact and insulate
for best possible reading.
3. Refer to the superheat table provided for proper system
superheat. Add charge to lower superheat or recover
charge to raise superheat.
Superheat Formula = Suct. Line Temp. - Sat. Suct.
Temp.
65
70
75
80
85
100
-
-
-
10
10
95
-
-
10
10
10
90
-
-
12
15
18
85
-
10
13
17
20
80
-
10
15
21
26
75
10
13
17
25
29
70
10
17
20
28
32
65
13
19
26
32
35
60
17
25
30
33
37
Ambient Condenser Inlet
Temp (°F Drybulb)
Return Air Temp. (°F Drybulb)
EXAMPLE:
a. Suction Pressure = 143
b. Corresponding Temp. °F. = 50
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 R410A Pressure vs. Temperature 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
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. Any time the
control is powered, the fault code history can be retrieved
