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minutes each cooling cycle or until the R- -to- -G circuit clos-
es or the demand for dehumidification is satisfied. Low- -
cooling airflow is the true on- -board CF (continuous fan)
selection as shown in Fig. 65.
b. When the R- -to- -Y/Y2 circuit is closed, R- -to- -G circuit is
open, and there is a demand for dehumidification, the fur-
nace blower motor BLWM will drop the blower airflow to
65 percent of high- -cooling airflow for a maximum of 10
minutes each cooling cycle or until the R- -to- -G circuit clos-
es or the demand for dehumidification is satisfied. High- -
cooling airflow is based on the A/C (air conditioning) se-
lection shown in Fig. 65.
c. When the "call for cooling" is satisfied and there is a de-
mand for dehumidification, the cooling blower- -off delay
is decreased from 90 sec to 5 sec.
6. Continuous Blower Mode
When the R- -to- -G circuit is closed by the thermostat, the
blower motor BLWM will operate at continuous blower air-
flow. Continuous blower airflow selection is initially based
on the CF (continuous fan) selection shown in Fig. 65. Fac-
tory default is shown in Fig. 65. Terminal EAC- -1 is ener-
gized as long as the blower motor BLWM is energized.
During a call for heat, the furnace control CPU will transi-
tion the blower motor BLWM to continuous blower airflow,
low- -heat airflow, or the mid- -range airflow, whichever is
lowest. The blower motor BLWM will remain ON until the
main burners ignite then shut OFF and remain OFF for the
blower- -ON delay (45 sec in low- -heat, and 25 sec in high- -
heat), allowing the furnace heat exchangers to heat up more
quickly, then restarts at the end of the blower- -ON delay pe-
riod at low- -heat or high- -heat airflow, respectively.
The blower motor BLWM will revert to continuous- -blower
airflow after the heating cycle is completed. In high- -heat,
the furnace control CPU will drop the blower motor BLWM
to low- -heat airflow during the selected blower- -OFF delay
period before transitioning to continuous- -blower airflow.
When the thermostat "calls for low- -cooling", the blower
motor BLWM will switch to operate at low- -cooling airflow.
When the thermostat is satisfied, the blower motor BLWM
will operate an additional 90 sec at low- -cooling airflow be-
fore transitioning back to continuous- -blower airflow.
When the thermostat "calls for high- -cooling", the blower
motor BLWM will operate at high cooling airflow. When
the thermostat is satisfied, the blower motor BLWM will op-
erate an additional 90 sec at high- -cooling airflow before
transitioning back to continuous- -blower airflow. When the
R- -to- -G circuit is opened, the blower motor BLWM will
continue operating for an additional 5 sec, if no other func-
tion requires blower motor BLWM operation.
Continuous Blower Speed Selection from Thermostat To
select different continuous- -blower airflow from the room
thermostat, momentarily turn off the FAN switch or push
button on the room thermostat for 1- -3 sec after the blower
motor BLWM is operating. The furnace control CPU will
shift the continuous- -blower airflow from the factory setting
to the next highest CF selection airflow as shown in Fig. 65.
Momentarily turning off the FAN switch again at the
thermostat will shift the continuous- -blower airflow up one
more increment. If you repeat this procedure enough you
will eventually shift the continuous- -blower airflow to the
lowest CF selection as shown in Fig. 65. The selection can
be changed as many times as desired and is stored in the
memory to be automatically used following a power
interruption.
NOTE:
If the blower- -off delay is set to the maximum, the
adjustable continuous- -fan feature is locked (i.e., fan speed cannot
be changed from its current setting).
7. Heat pump
See Fig. 38 and 39 for thermostat connections.
When installed with a heat pump, the furnace control auto-
matically changes the timing sequence to avoid long blower
off times during demand defrost cycles. Whenever W/W1 is
energized along with Y1 or Y/Y2, the furnace control CPU
will transition to or bring on the blower motor BLWM at
cooling airflow, low- -heat airflow, or the mid- -range airflow,
whichever is lowest. The blower motor BLWM will remain
on until the main burners ignite then shut OFF and remain
OFF for 25 sec before coming back on at heating airflow.
When the W/W1 input signal disappears, the furnace con-
trol begins a normal inducer post- -purge period while
changing the blower airflow. If Y/Y2 input is still energized
the furnace control CPU will transition the blower motor
BLWM airflow to cooling airflow. If Y/Y2 input signal dis-
appears and the Y1 input is still energized the furnace con-
trol CPU will transition the blower motor BLWM to low- -
cooling airflow. If both the Y1 and Y/Y2 signals disappear
at the same time, the blower motor BLWM will remain on at
low- -heat airflow for the selected blower- -OFF delay period.
At the end of the blower- - OFF delay, the blower motor
BLWM will shut OFF unless G is still energized, in which
case the blower motor BLWM will operate at continuous
blower airflow.
Component Self- - Test
Refer to "Component Self Test" in the Service and Maintenance
section for details.
87
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