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1.
After several minutes the main burners must go OFF.
Blower will continue to run.
2.
Remove air restrictions and main burners will relight after a
cool down period of a few minutes.
Adjust the thermostat setting below room temperature.
1.
Main burners must go OFF.
2.
Circulating Air Blower will continue to run for 90, 120, 150 or
180 seconds, depending on the setting.
NOTE: If necessary, adjust fan OFF delay settings to obtain
satisfactory comfort level.
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 Startup
NOTE: The outdoor temperature must be 60°F or higher before
making adjustments to charge.
NOTE: Check all manual reset limit controls in heating circuit if
cooling mode does not operate.
Compressor Protection Devices
The compressor includes components which are designed to
protect the compressor against abnormal operating conditions.
Refrigerant Charge Check
After completing airflow measurements and adjustments the
unit's refrigerant charge must be checked. The unit comes
factory charged, but this charge is based on 325 CFM per ton
and minimum ESP per AHRI test conditions (generally between
.15-.28 ESP). When air quantity or ESP is different than above,
the refrigerant charge must be adjusted to the proper amount.
All package units with fixed orifice devices are charged using the
super heat method at the compressor suction line.
After superheat is adjusted it is recommended to check unit
sub-cooling at the condenser coil liquid line out. For charge
adjustments, see superheat and sub-cooling charts show for each
model.
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.
Ambient Condenser Inlet
Temp (°F Drybulb)
100
95
90
85
80
75
70
65
60
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.
17
Return Air Temp. (°F Drybulb)
65
70
75
80
-
-
-
10
-
-
10
10
-
-
12
15
-
10
13
17
-
10
15
21
10
13
17
25
10
17
20
28
13
19
26
32
17
25
30
33
85
10
10
18
20
26
29
32
35
37
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