Carrier 59MN7B Installation, Start-Up, Operating And Service And Maintenance Instructions page 95

furnace blower motor BLWM
High-cooling airflow is based on the A/C selection shown in Fig.
65.
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
Fig. 65.
4. Dehumidification Mode
See Fig. 36 and 38 for thermostat connections.
The dehumidification output, HD or DHUM on the 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. Once 24 vac is detected by the furnace control,
dehumidification capability is activated. If the DHUM input is
removed for more than 48 hours, the furnace control reverts back
to non-dehumidification mode.
The cooling operation described above in the Cooling Mode
section also applies to Dehumidification mode. 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 86%
of low cooling airflow which is the SW3 selection as
shown in Fig. 65.
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 86% of high-cooling airflow. High-cooling airflow is
based on the A/C selection shown in Fig. 65.
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.
Super Dehumidify Mode
Super-Dehumidify mode can only be entered if the furnace control
is in the Dehumidification mode and there is a demand for
dehumidification. The cooling operation described in Cooling
Mode section above also applies to Super Dehumidify Mode. The
exceptions are listed below:
1. Low cooling – When the R to Y1 circuit is closed, R to G
circuit is open, and there is a demand for dehumidification,
the furnace blower motor BLWM will drop the blower air-
flow to 65% of low-cooling airflow for a maximum of 10
minutes each cooling cycle or until the R to G circuit closes
or the demand for dehumidification is satisfied. Low-cool-
ing airflow is the SW3 selection as shown in Fig. 65.
2. High cooling – When the R to Y/Y2 circuit is closed, R to
G circuit is open, and there is a demand for dehumidifica-
tion, the furnace blower motor BLWM will drop the blower
airflow to 65% of high-cooling airflow for a maximum of
10 minutes each cooling cycle or until the R to G circuit
closes or the demand for dehumidification is satisfied.
High-cooling airflow is based on the A/C selection shown
in Fig. 65.
3. Cooling off-delay – When the "call for cooling" is satisfied
and there is a demand for dehumidification, the cooling
at high-cooling airflow. blower-off delay is decreased from 90 seconds to 5 sec-
onds.
Continuous Blower Mode
When the R to G circuit is closed by the thermostat, the blower
motor BLWM will operate at continuous blower airflow.
Continuous blower airflow selection is initially based on the SW3
selection shown in Table 7. Factory default is shown in Table 7.
Terminal EAC-1 is energized as long as the blower motor BLWM
is energized.
During a call for heat, the furnace control CPU will transition the
blower motor BLWM
minimum-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 seconds in intermediate heat, and 25 seconds in
maximum-heat), allowing the furnace heat exchangers to heat up
more quickly, then restarts at the end of the blower-ON delay
period at modulating or maximum-heat airflow respectively.
The blower motor BLWM will revert to continuous-blower
airflow after the heating cycle is completed. When the thermostat
satisfies, the furnace control CPU will drop the blower motor
BLWM to minimum-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 operate at low-cooling airflow. When the thermostat
is satisfied, the blower motor BLWM will operate an additional 90
seconds at low-cooling airflow before 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 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
continue operating for an additional 5 seconds, if no other function
requires blower motor BLWM operation.
Continuous Blower Speed Selection from Thermostat
To select different continuous-blower airflows from the room
thermostat, momentarily turn off the FAN switch or push button
on the room thermostat for 1-3 seconds 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 SW3 selection
airflow as shown in Table 7. 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 SW3 selection as shown in Table 7. The selection can
be changed as many times as desired and is stored in the memory
to be automatically used following a power interruption.
Heat Pump
See Fig. 36 and 38 for thermostat connections. When installed
with a heat pump, the furnace control automatically 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, minimum-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 seconds before coming back on at
modulating heat airflow. When the W/W1 input signal
disappears, the furnace control 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
95
to continuous blower airflow,