20
3. The igniter is energized and is allowed to preheat.
4. The gas valve is energized delivering gas to the burners
and starting combustion.
5. The control checks for a signal from the flame sensor
within seven seconds after the gas valve is energized.
Gas will only continue to flow if a signal is present.
6. The control waits 30 seconds and turns on the air
circulation blower to the speed that was selected for
heating operation.
7. The thermostat is satisfied and opens.
8. The control de-energizes the gas valve.
9. After a 15 second delay while flue products are purged
from the furnace heat exchanger, the induced draft
blower motor is de-energized.
10. The air circulation blower has an adjustable delay-off
timing of 60, 90, 120 or 180 seconds (starting from the
time the gas valve closes). This allows more heat from
the furnace to be transferred to the conditioned space.
After this time has elapsed, the blower will be de-
energized.
NORMAL COOLING SEQUENCE - INTEGRATED
IGNITION CONTROL
With the room thermostat in the FAN-AUTO position, the
indoor air circulation blower and outdoor condensing unit
will be energized when a call for cooling occurs. When the
call for cooling ends, the outdoor condensing unit will be de-
energized. The indoor air circulation blower will continue to
run for 45 seconds.
OTHER ITEMS
Constant Fan.
During normal operation, the air circu-
lation blower will continually run at “Cooling” speed as
long as power is present at terminal G. If a call for heat
occurs, the blower will run at heating speed throughout
the heating cycle.
If a trip on high/auxiliary/rollout limit occurs, the air
circulation blower will run at “Heating” speed. Even if
power is present at terminal G, the blower will run at
heating speed until the limit closes.
X. Start-Up, Adjustments, and Checks
GENERAL OPERATION
This furnace is equipped with an electronic ignition device
to light the burners and an induced draft blower to exhaust
combustion products.
An interlock switch prevents furnace operation if the blower
door is not in place. Keep the blower access doors in place
except for inspection and maintenance.
This furnace is also equipped with a self-diagnosing elec-
tronic control module. In the event a furnace component is
not operating properly, the control module LED will flash
on and off in a factory-programmed sequence, depending
on the problem encountered. This light can be viewed
CENTRAL
RETURN
GRILLE
FI
LT
E
R
SIDE RETURN
EXTERNAL FILTER
RACK KIT
(EITHER SIDE)
FI
LT
E
R
FI
LT
E
R
SIDE RETURN
INTERNAL FILTER
RETENTION
(EITHER SIDE)
AIR FLOW
F I L T E R
Figure 26
Possible Upright Upflow
Filter Locations
AIR FLOW
FILTE
R
FI
LTE
R
FI
LTE
R
FILTER
ACCESS
DOOR
CENTRAL
RETURN
GRILLE
RETURN
DUCT
FILTER
SUPPORT
BRACKET
(PROVIDED)
Figure 27
Possible Upright Counterflow
Filter Locations
HORIZONTAL INSTALLATIONS
Filters must be installed in either the central return register
or in the return air duct work.
Refer to the Specification Sheet for recommended mini-
mum filter sizes.
IX. Sequence of Operation (Integrated
Ignition Control)
Refer to Timing Charts for sequencing.
NORMAL HEATING SEQUENCE
1. Thermostat calls for heat.
2. The induced draft blower is energized.
