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immediately. The control de-energizes the induced draft
motor and runs the indoor blower motor continuously
while the limit switch is open.
NOTE: This unit has two special features
programmed into the furnace control board for
safety and proper unit operation.
Thaw Cycle Start Up / Shutdown
The vent pressure switch is constantly monitored
throughout the ignition cycle. If after 1 minute of burner
ignition the vent pressure switch remains open, the
control will de-energize the gas valve, energize the main
blower, and begin another ignition sequence after a 30
second inter-purge. If after 5 cycles the pressure switch
fails to close the unit will lockout for a period of one hour.
The blower stays energized for the selected blower off
delay period. This feature only activates if the unit is off
for extended periods of time between heating cycles in
extremely cold weather which could lead to ice formation
over the vent pressure tap or the switch itself is faulty.
Any ice formation will clear after one or two trials. One
hour lockout period can be terminated by shutting off the
thermostat for 5-10 seconds or main power to unit for
1-2 seconds.
Blocked Vent / Condensate Disposal Shut
Down
The pressure switch is constantly monitored throughout
the ignition cycle. After normal operation is established,
if the pressure switch opens for more than 2-3 seconds,
the unit will shutdown and go into a 1 hour lockout. The
control will de-energize the gas valve and inducer motor
after normal post purge timing, energize the main blower,
and store the fault in non-volatile memory. The blower
stays energized for the selected blower off delay period.
The ignition control will display a flash code of Green-OFF
/ Red-Flash to indicate system fault for "Pressure Switch
Loss Due To Blocked Vent / Condensate Disposal". One
hour lockout period can be terminated by shutting off the
thermostat for 5-10 seconds or main power to unit for
1-2 seconds.
After expiration of the 1 hour lockout period or manual
reset, the control will attempt a new ignition cycle. If the
pressure switch fails to close on first ignition attempt of
one minute burn time and a non-volatile condensate/vent
fault is set, control will go back to lockout and display the
condensate/vent fault flash code. Fault remains stored in
non-volatile memory even with cycling of thermostat or
main power. NOTE: Nonvolatile blocked condensate/
vent fault will be cleared when a complete thermostat
heat demand is satisfied in steady state heat mode.
Cooling Mode - Single Stage Operation
1. On a call for cooling, the thermostat closes applying 24
VAC to the G & Y terminals on the low voltage terminal
strip.
2. The G terminal applies 24VAC to the G terminal of the
integrated control, energizing the main circulating blower
circuit at the selected cooling speed.
20
3. The Y terminal applies 24VAC to the contactor energizing
the outdoor compressor and fan.
4. When the thermostat is satisfied, the contactor and
integrated control de-energize. Compressor and outdoor
fan will stop running.
5. The circulating blower motor de-energizes after a 60
second delay.
De-Humidification Control
If installing a humidistat, install it in the return air duct
as directed in the installation instructions included in the
accessory kit. Run the humidistat wiring through the low
voltage wire entrance of the packaged unit. Connect one
side of the humidistat to the R terminal of the low voltage
field connection board and connect the other side to the
DEHUM terminal on the blower control board. Wire the
humidistat to close on rise in humidity.
For dehumidification, the DEHUM input on the FSHE board
(Figure 10, page 31) can be used to control this function.
If the DEHUM input is active and the unit is operating, the
blower CFM is 75% of cooling for the operating speed.
Fan Mode
1. On a call for fan only operation, the thermostat applies
24 VAC to the G terminal connected to the G terminal
of the integrated control.
2. The circulating blower is energized immediately and
will operate approximately 50% of the selected airflow
when no call for heqating or cooling is present
NOTE: If a call for heat occurs, the circulating blower
de-energizes prior to normal heating cycle.
COMPONENT FUNCTIONS
Flame Roll-Out Control - The flame roll-out control acts
to verify that the burner flame is being drawn into the heat
exchanger tubes. If the burner flame is not being drawn
into the heat exchanger tubes, the roll-out control will
open within several seconds and the integrated control
diagnostic light will flash one time. The circulating air
blower and combustion blower will continue to operate if
the flame roll-out control opens.
Flame Sensor - The flame sensor acts to prove that
flame has carried over from the ignitor to the right-most
burner. If no flame is sensed, the unit will be shut down
automatically.
Gas Valve - The gas valve controls the flow of gas to the
burners. When the gas valve is energized it automatically
opens and regulates the gas pressure in the manifold.
Inducer Hall Effect Sensor Switch - This sensor verifies
the inducer motor is running in the event of power outages
or during long intervals of unit off time where pressure
switch reading could be lost due to ice formation over
the pressure switch port. This will clear within the first or
second thaw cycle routine.
Pressure Switch - The pressure switch verifies that the
inducer motor is drawing the combustion gases through
the heat exchanger tubes and venting the gases through
the vent system.
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