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Limit Check
Check limit control operation after 15 minutes of operation
by blocking the return air grille(s).
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.
Compressor Protection Devices
The compressor includes components which are de-
signed to protect the compressor against abnormal
operating conditions.
Cooling Refrigerant Charging
This unit must not be used as a "construction heater" during
the finishing phases of construction on a new structure.
This type of use may result in premature failure of the unit
due to extremely low return air temperature and exposure
to corrosive or very dirty atmospheres.
Check unit charge before putting the cooling section into
full operation. The unit has a thermostatic expansion valve
metering device. To ensure the unit is properly charged
for the intended application, check the unit refrigerant
subcooling at the condenser. The refrigerant subcooling 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
subcooling at the condenser is adjusted for each applica-
tion. As the outdoor ambient temperature rises the sub-
cooling decreases and as the outdoor ambient temperature
lowers, the subcooling increases.
WARNING
Checking Subcooling
NOTE: Units with a TXV should be charged to Sub-
cooling only.
EXAMPLE:
a. Liquid Line Pressure = 417 PSI
b. Corresponding Temp. = 120°F
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 specifica-
tion sheet or technical information manual for the design
subcooling range for your unit.
SUBCOOLING FORMULA = SATURATED LIQUID LINE
TEMPERATURE - LIQUID LINE TEMPERATURE
Checking Superheat
EXAMPLE:
a. Suction Pressure = 143 PSI
b. Corresponding Temp. = 50°F
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.
SUPERHEAT = SUCTION LINE TEMP - SAT. SUCTION
TEMP.
Superheat Adjustment
NOTE: Superheat adjustments should not be made
until indoor ambient conditions have stabilized.
This could take up to 24 hours depending on indoor
temperature and humidity. Before checking su-
perheat, run the unit in cooling for 10-15 minutes
or until refrigerant pressures stabilize. Use the
following guidelines and methods to check unit
operation and ensure that the refrigerant charge
is within limits.
For TXV systems, to adjust superheat, unscrew the cover
from the expansion valve, locate the adjustment screw, and
turn it clockwise (in) to increase superheat or counterclock-
wise (out) to decrease superheat. It is recommended to make
small adjustments at a time, 1/8 - 1/4 turn increments. Replace
adjustment cap. Wait a minimum of 10 minutes between ad-
justments to allow time for the TXV and pressures to stabilize.
Refrigerant Charge Check
NOTE: For optimal performance, follow charging
in structions below.
(Units with Fixed Orifice Devices)
All package units with fixed orifice devices are charged
using the superheat method at the compressor suction line.
To increase super heat, remove charge and to decrease
super heat, add charge. After superheat is adjusted, it is
recommended to check unit subcooling at the condenser
coil liquid line. See Design Superheat and Subcooling table
for targets on each model.
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