International comfort products F8MVL Installation Instructions Manual page 51

closed. The blower motor BLWM will transition to
low−heat airflow five seconds after the R−to−W2
circuit opens.
3. Cooling mode
The thermostat "calls for cooling".
a. Single−Speed Cooling−
See Figure 27 for thermostat connections
The thermostat closes the R−to−G−and−Y circuits.
The R−to− Y circuit starts the outdoor unit, and the
R−to−G−and−Y/Y2 circuits start the furnace blower
motor BLWM on cooling airflow. Cooling airflow is
based on the A/C selection shown in Table 10. The
electronic air cleaner terminal EAC−1 is energized
with 115 vac when the blower motor BLWM is oper-
ating.
When the thermostat is satisfied, the R−to−G−and−Y
circuits are opened. The outdoor unit will stop, and
the furnace blower motor BLWM will continue operat-
ing at cooling airflow for an additional 90 seconds.
Jumper Y/Y2 to DHUM to reduce the cooling off−
delay to 5 seconds. (See Figure 26)
b. Two−Stage Thermostat and Two−Speed Cooling
See Figure 28 for thermostat connections
The thermostat closes the R−to−G−and−Y1 circuits for
low−cooling or closes the R−to−G−and−Y1−and−Y2 circuits
for high−cooling. The R−to−Y1 circuit starts the outdoor unit on
low−cooling speed, and the R−to−G−and−Y1 circuit starts the
furnace blower motor BLWM at low−cooling airflow which is
the CF (continuous fan) selection as shown in Table 10. The
R−to−Y1−and−Y2 circuits
high−cooling speed, and the R−to− G−and−Y/Y2 circuits start
the furnace blower motor BLWM at high−cooling airflow.
High−cooling airflow is based on the A/C (air conditioning)
selection shown in Table 10.
The electronic air cleaner terminal EAC−1 is energized with
115 vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R−to−G−and−Y1 or
R−to− G−and−Y1−and−Y2 circuits are opened. The outdoor
unit stops, and the furnace blower BLWM and electronic air
cleaner terminal EAC−1 will remain energized for an additional
90 seconds. Jumper Y1 to DHUM to reduce the cooling
off−delay to 5 seconds. (See Figure 26)
4. Dehumidfy Mode
See Figure 27−Figure 33 for thermostat connections.
The H output on the humidify sensing thermostat should
be connected to the furnace control thermostat terminal
DHUM. When there is a dehumidify demand, the DHUM
input is activated, which means 24 vac signal is removed
from the DHUM input terminal. In other words, the DHUM
input logic is reversed. The DHUM input is turned ON
when no dehumidify demand exists. Activation/Deactiva-
tion
Once 24 vac is detected by the furnace control on the
DHUM input, the furnace control operates in dehumidify
mode. If the DHUM input is low for more than 48 hours, the
furnace control reverts back to non−dehumidify mode.
The cooling operation described in item 3. above also ap-
plies to operation with a humidity sensing thermostat. The
exceptions are listed below:
a. Low Cooling−When the R−to−G−and−Y1 circuit is
closed and there is a demand for dehumidification,
the furnace blower motor BLWM will drop the blower
airflow to 90 percent of low−cooling airflow which is
the CF (continuous fan) selection as shown in Table
10.
b. High−Cooling−When the R−to−G−and−Y/Y2 circuit
is closed and there is a demand for dehumidification,
the furnace blower motor BLWM will drop the blower
airflow to 90 percent of high−cooling airflow. High−
cooling airflow is based on the A/C (air conditioning)
selection shown in Table 10.
441 01 2122 01
start the outdoor unit
Specifications are subject to change without notice.
c. Cooling off−delay−When the "call for cooling" is
satisfied and there is a demand for dehumidification,
the cooling blower−off delay is decreased from 90
seconds to 5 seconds.
5. 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 Table 10.
Factory default is shown in Table 10. Terminal EAC−1 is
energized as long as the blower motor BLWM is energized.
During the initial call for heat, the furnace control CPU will
keep the blower motor BLWM at continuous blower airflow.
The blower motor BLWM will remain ON until the main
burners ignite then shut OFF and remain OFF for the
blower−ON delay (45 seconds in low−heat, and 25
seconds in high−heat), allowing the furnace heat ex-
changers to heat up more quickly, then restarts at the end
of the blower−ON delay period 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 seconds at low−cooling air-
flow before transitioning back to continuous−blower airflow.
on
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 operate
an additional 90 seconds at high−cooling airflow before
transitioning back to continuous−blower airflow. When the
R−to−G circuit is opened, the blower motor BLWM will con-
tinue operating for an additional 5 seconds, if no other
function requires blower motor BLWM operation.
6. Heat pump
See Figure 29 − Figure 33 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 con-
trol CPU will transition to or bring on the blower motor BL-
WM at cooling airflow, low−heat airflow, whichever is low-
est. The blower motor BLWM will remain on until the main
burners ignite then shut OFF and remain OFF for 25
seconds before coming back on at heating airflow. When
the W/W1 input signal disappears, the furnace control be-
gins a normal inducer post−purge period while changing
the blower airflow. If Y/Y2 input is still energized the fur-
nace control CPU will transition the blower motor BLWM
airflow to cooling airflow. If Y/Y2 input signal disappears
and the Y1 input is still energized the furnace control CPU
will transition the blower motor BLWM to low−cooling air-
flow. 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 air-
flow.
7. Component test
The furnace features a component test system to help dia-
gnose a system problem in the case of a component fail-
ure. To initiate the component test procedure, ensure that
there are no thermostat inputs to the control and all time
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