Cooling Mode; Dehumidify Mode; Single- -Speed Cooling; Single- -Stage Thermostat And Two- -Speed Cooling (Adaptive Mode) - Carrier PG9UAA Troubleshooting Manual

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
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.)
b. Single- -Stage Thermostat and Two- -Speed Cooling
(Adaptive Mode)
This furnace can operate a two- -speed cooling unit with a
single- -stage thermostat because the furnace control CPU includes a
programmed adaptive sequence of controlled operation, which
selects low- -cooling or high- -cooling operation. This selection is
based upon the stored history of the length of previous cooling
period of the single- -stage thermostat.
Table 1 – Cooling Tonnage vs. Airflow (CFM)
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
SETUP SWITCH SW2/SW3 POSITIONS
MODEL
SIZE
040, 060, 3T-080 DEF. 525 700
2
5T-080, 100 DEF. 700 875
2
120 DEF. 700 875
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON)
SETUP SWITCH SW2/SW3 POSITIONS
MODEL
SIZE
040, 060, 3T-080 DEF. 600 800
2
5T-080, 100 DEF. 800 1000
2
120 DEF. 800 1000
1. DEFAULT A/C AIRFLOW WHEN A/C SWITCHES ARE IN OFF POSITION
2. DEFAULT CONT. FAN AIRFLOW WHEN CF SWITCHES ARE IN OFF POSITION
3. SWITCH POSITIONS ARE ALSO SHOWN ON FURNACE WIRING DIAGRAM
NOTE: The air conditioning relay disable jumper ACRDJ must
be connected to enable the adaptive cooling mode in response to a
call for cooling. (See Fig. 1.) When in place the furnace control
CPU can turn on the air conditioning relay ACR to energize the
Y/Y2 terminal and switch the outdoor unit to high- -cooling.
The furnace control CPU can start up the cooling unit in either
low- - or high- -cooling. If starting up in low- -cooling, the furnace
control CPU determines the low- -cooling on- -time (from 0 to 20
minutes) which is permitted before switching to high- -cooling.
If the power is interrupted, the stored history is erased and the
furnace control CPU will select low- -cooling for up to 20 minutes
and then energize the air conditioning relay ACR to energize the
Y/Y2 terminal and switch the outdoor unit to high- -cooling, as
long as the thermostat continues to call for cooling. Subsequent
selection is based on stored history of the thermostat cycle times.
The wall thermostat "calls for cooling", closing the R to G- -and- -Y
circuits. The R to Y1 circuit starts the outdoor unit on
low- -cooling speed, and the R to G- -and- -Y1 circuits starts the
875 1050 1225 1225 1225
1
1050 1225 1400 1750 1750
1
1050 1225 1400 1750 2100
2 1
1000 1200 1400 1400 1400
1
1200 1400 1600 2000 2000
1
1200 1400 1600 2000 2100
2 1
A10472
furnace blower motor BLWM at low- -cooling airflow which is the
true on- -board CF selection as shown in Table 1.
If the furnace control CPU switches from low- -cooling to
high- -cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay ACR is
energized the R to Y1- -and- -Y2 circuits switch the outdoor unit to
high- -cooling speed, and the R to G- -and- -Y1- -and- -Y/Y2 circuits
transition the furnace blower motor BLWM to high- -cooling
airflow. High- -cooling airflow is based on the A/C selection shown
in Table 1.
NOTE: When transitioning from low- -cooling to high- -cooling the
outdoor unit compressor will shut down for 1 minute while the
furnace blower motor BLWM transitions to run at high- -cooling
airflow.
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- -Y circuit 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.)
c. Two- -Stage Thermostat and Two- -Speed Cooling
NOTE: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. (See Fig. 1.)
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. The R to 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.)

4. DEHUMIDIFY MODE

The dehumidification output, 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 on the DHUM
input, the furnace control operates in Thermidistat 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 applies to
operation with a dehumidify enabled thermostat. The exceptions
are listed below:
a. 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 true on- -board CF selection
as shown in Table 1.
b. 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
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