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LO COOL
U6
HI COOL
U7
LO HEAT
U4
U3
HI HEAT
U5
P1
SPEEDUP
F1
SW1
FAULT
BLOWER
STAGE
ECON
RECALL
OFF DELAY
DELAY
Control Board (Top)
Unit Shutdown
1. Set the thermostat to lowest setting.
2. Turn off the electrical power supply to the unit.
3. Remove the heat exchanger door on the side of the
unit by removing screws.
4. Move the gas control valve switch to the OFF
position. Do not force.
5. Close manual gas shutoff valve external to the unit.
6. Replace the heat exchanger door on the unit.
7. If cooling and/or air circulation will be desired, turn
ON the electrical power.
Cooling Start-up
NOTE: Check all manual reset limit controls in heating
circuit if cooling mode does not operate.
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.
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.
K2
K1
C W1 W2G Y1 Y2
R
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.
Ambient
Condenser Inlet
65
Temp (°F Drybulb)
100
-
95
-
90
-
85
-
80
-
75
10
70
10
65
13
60
17
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.
18
Return Air Temp. (°F Drybulb)
70
75
80
-
-
10
-
10
10
-
12
15
10
13
17
10
15
21
13
17
25
17
20
28
19
26
32
25
30
33
85
10
10
18
20
26
29
32
35
37
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