Fedders F80A - Manual (Page 18)

17
MODEL F80A
START UP PROCEDURES
This furnace is equipped with a hot surface ignition (HSI) device.
Each time that the room thermostat calls for heat, the HSI lights
the main burners directly. See the lighting instructions on the
furnace.
TO START THE FURNACE:
1. Remove the burner compartment access door.
2. Shut off the electrical power to the furnace and set the
room thermostat to its lowest setting.
3. Ensure that the ignition system control switch on the White-
Rodgers 36G22 gas valve is in the “ON” position.
4. Replace the burner compartment access door.
5. Restore electrical power to the furnace.
6. Set the room thermostat to a point above room
temperature to light the furnace.
7. After the burners are lit, set the room thermostat to the
desired temperature.
TO SHUT DOWN THE FURNACE:
1. Set the room thermostat to its lowest setting.
2. Remove the burner compartment access door.
3. The ignition system control switch on the White-Rodgers
36G22 gas valve may be switched to the “OFF” position.
4. The furnace appliance shutoff valve may be closed if
desired.
WARNING
SHOULD OVER HEATING OCCUR, OR THE GAS BURNERS FAIL
TO SHUT OFF, CLOSE THE MANUAL GAS VALVE FOR THE
FURNACE BEFORE SHUTTING OFF THE ELECTRICAL POWER
TO THE FURNACE. FAILURE TO DO SO CAN CAUSE AN
EXPLOSION OR FIRE RESULTING IN PROPERTY DAMAGE,
PERSONAL INJURY OR LOSS OF LIFE.
Sequence if the furnace does not light up or
detect flame:
1. See steps 1 through 5 for initial operation.
2. If pressure switch contacts are closed; and have failed
to open since the last cycle, all subsequent steps will
fail to occur.
3. If the burners fail to light, or if the flame is not sensed,
the gas valve closes, and, providing that there have
been less than 5 trials for ignition, sequence returns to
sequence of operation Step 4. If this was the 5th trial
for ignition, the ignition system goes into a 60 minute
lockout condition, and then reattempts the sequence
at Step 4.
In addition, if during the burner firing, the flame signal
is lost, the gas valve will close and the ignition
sequence will begin again at Step 4 above. If the flame
sensing signal is lost more than 5 times during a
furnace cycle, the gas valve will close, and the ignition
sequence goes into a 5 second postpurge; the induced
blower stops. The ignition system goes into a 60
minute lockout condition then reattempts the
sequence at Step 4 above.
The 60 minute lockout sequence will repeat itself
indefinitely. Lowering the room thermostat setting
below room temperature for approximately 10
seconds, or shutting off the electrical supply to the
furnace for approximately 10 seconds may interrupt
the 60 minute lockout.
4. Furnace continues to run in this state until the room
thermostat heating contacts open in response to raised
room temperature.
5. With the thermostat heating contacts open, the burner
flames extinguish immediately, the induced blower
stops after a 5 second postpurge period. Pressure
switch contacts open.
6. The circulating fan continues to run until timed out in
60 to 180 seconds, depending on the 50A55-250
Integrated Furnace Control dipswitch settings.
Additional information is available in the Troubleshooting
section that starts on page 22 of this manual.
SEQUENCE OF OPERATION
White-Rodgers 36G22 Gas Valve &
White-Rodgers 50A55-250 Integrated Furnace Control
1. Room temperature drops causing the room thermostat
heating contacts to close.
2. The induced blower begins a prepurge cycle of 15 seconds.
3. The pressure switch contacts close.
4. After the prepurge period, the hot surface igniter heats up;
10 seconds on a first try, maximum 14 seconds on a
subsequent retry.
5. The gas valve opens for a 7 second trial for ignition. The
gas burners light, the igniter shuts off. (See next section for
sequence of operation in the event of a flame failure).
6. The circulating fan begins 30 seconds after flame is sensed.
7. Furnace continues to run in this state until the room
thermostat heating contacts open in response to raised
room temperature.
8. With the thermostat heating contacts open, the burner
flames extinguish immediately, the induced blower stops
after a 5 second postpurge period. The pressure switch
contacts open.
9. The circulating fan continues to run until timed out in 60 to
180 seconds, depending on the 50A55-250 Dip Switch
settings.