17
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 120, 135
or 150 seconds, (single stage models) or 90, 120, 150,
or 180 seconds (two-stage models), depending on the
setting.
Control Board (Single Stage)
LO COOL
HI COOL
LO HEAT
HI HEAT
U6
U7
U4
U5
U3
K2
K1
P1
ECON
STAGE
DELAY
SPEEDUP
SW1
FAULT
RECALL
BLOWER
OFF DELAY
F1
R
C
W1 W2
G
Y1 Y2
Control Board (Two-Stage)
NOTE:
If necessary, adjust fan OFF delay settings to obtain satis
-
factory 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:
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.
WARNING
T
O
PR
EVENT
PE
RSONAL I NJURY OR D EATH, ALWAYS D ISCONNECT E LECTRICAL
PO
WER BEFORE I NS
PE
CTING OR S ERVICING T HE U NIT.
A
LL CO
MP
RESSOR
PR
OTECTION D EVICES R ESET AUTOMATICALLY, ENERGIZING T HE C ONTACTOR
AND OUTDOOR FAN.
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 shown for
each model. See superheat chart below.
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.
EXAMPLE:
a. Suction Pressure = 143
b. Corresponding Temp. °F. = 50
