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This furnace is equipped with a direct ignition control. Each time
the room thermostat calls for heat, the ignitor lights the main
burners directly. See the lighting instructions on the furnace.
TO START THE FURNACE
1. Remove the burner compartment control access door.
2. IMPORTANT: Be sure that the manual gas control has been
in the "OFF" position for at least five minutes. Do not attempt
to manually light the main burners.
3. Turn off the furnace electrical power and set the room ther-
mostat to its lowest setting.
4. Turn the gas control to the "ON" position or move the gas
control lever to the "On" position.
5. Replace the burner compartment control access door.
6. Turn on the furnace electrical power.
7. Set the room thermostat to a point above room temperature
to light the main burners. The heat call should be adequate
to activate the high stage gas heat – generally, the thermo-
stat setpoint should be more than 2°F above room tempera-
ture. Consult your thermostat specs to be sure.
8. Operate high gas heat for a minimum period of 15 minutes
and adjust input rate (See Section of this book titled Adjust-
ing Input Rate ).
9. Once high heat operation has been successfully verified and
rate adjusted, the thermostat should be adjusted to set the
heat call to low stage. This is generally with the heating set-
point at about 1°F above room temperature. Consult your
thermostat specs to be sure.
10. Operate low gas heat for a minimum period of 15 minutes
and adjust input rate (page 56).
TO SHUT DOWN THE FURNACE
1. Set the room thermostat to its lowest setting and wait for fur-
nace to shut down.
2. Remove the burner compartment control access door.
3. Shut off the gas to the main burners by turning the gas con-
trol to the "OFF" position.
SEQUENCE OF OPERATION
HONEYWELL CONTROLS Integrated Controls
with Direct Spark Ignition.
1. Each time the thermostat "W" (Heating) contacts close
(legacy) or a communicating heat call is transmitted to the
furnace control from a communicating thermostat, the fur-
nace control checks to make sure that both pressure
switches are open. This is true of a low or high heat call as
"W" is energized on either call. Next the induced draft
blower (inducer) begins a pre-purge cycle at high stage.
2. The air proving negative pressure switches (both low and
high) close. Inducer will then immediately shift to low speed.
3. After the 30-second pre-purge, the gas valve opens on low
stage for an 8-second trial for ignition.
START-UP PROCEDURES
SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY
FAIL TO SHUT OFF, CLOSE THE MANUAL GAS VALVE
FOR THE APPLIANCE BEFORE SHUTTING OFF THE
ELECTRICAL SUPPLY. FAILURE TO DO SO CAN CAUSE
AN EXPLOSION OR FIRE RESULTING IN PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.
4. The spark igniter is energized to light the gas burners and
stays energized for the up to 7 seconds after the gas
valve opens.
5. Eight seconds after the gas valve opens the remote flame
sensor must prove flame ignition for one second using
the process of flame rectification. If the burners don't light,
the system goes through another ignition sequence. It does
this up to four times before entering a 1-hour lockout.
6. Twenty seconds after flame is sensed, the gas valve is set to
the thermostat demand (low or high) and the main blower
will be energized at either the low or high gas heat stage de-
pending on the thermostat demand.
7. When the thermostat "W" (legacy) or communicated heat call
ends, the gas valve closes, flame is extinguished, the in-
duced draft blower stops after a 10-second post-purge, and
the negative pressure switch opens.
8. The main blower continues until timed off by the setting on
the integrated furnace control board.
35
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