Cooling Mode; Dehumidification Mode - ICP 9MAC/E series Troubleshooting Manual

gets within 15% of the required intermediate-heat RPM the
furnace control CPU will start a 5 second blower airflow change
delay. After the 5 second blower airflow change delay is
completed the blower airflow will transition to intermediate-
heat airflow.

COOLING MODE

The thermostat "calls for cooling".
1. Single-Speed Cooling
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 1.
The electronic air cleaner terminal EAC-1 is energized with 115
vac when the blower motor BLWM is operating.
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 operating at cooling airflow for an
additional 90 seconds. Jumper Y/Y2 to DHUM to reduce the
cooling off-delay to 5 seconds. (See Fig. 1.)
2. Two-Stage Thermostat and Two-Speed Cooling
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 true
on-board CF selection as shown in Table 1.
Y1-and-Y2 circuits start the outdoor unit on 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 selection shown in Table 1.
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. 1.)

DEHUMIDIFICATION MODE

The dehumidification output, D or DHUM on a 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 on the DHUM input,
dehumidification capability is activated. If the DHUM input is low
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:
The R to
Low Cooling - When the R to G-and-Y1 circuit is closed and
1.
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 true on-board CF selection as
shown in Table 1.
High Cooling - When the R to G-and Y/Y2 circuit is closed
2.
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 Table 1.
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