Cooling Mode; Single-Speed Cooling; Single-Stage Thermostat And Two-Speed Cooling (Adaptive Mode); Two-Stage Thermostat And Two-Speed Cooling - Bryant 355CAV A Series Troubleshooting Manual

4.

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
AIR CONDITIONING (A/C) OR CONTINUOUS-FAN (CF)
AIRFLOW SELECTION CHART
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
SETUP SWITCH SW3 POSITIONS
MODEL
SIZE
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 SW3 POSITIONS
MODEL
SIZE
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.
875 1050 1225 1225
1
1050 1225 1400 1750
1
1050 1225 1400 1750
2 1
1000 1200 1400 1400
1
1200 1400 1600 2000
1
1200 1400 1600 2000
2 1
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
outdoor unit to high-cooling, as long as the thermostat
continues to call for cooling.
based on stored history of the thermostat cycle times.
The wall thermostat "calls for cooling", closing the
R to G-and-Y circuits.
outdoor unit on low-cooling speed, and the R to G-and-Y1
circuits starts the 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.
blower BLWM and electronic air cleaner terminal EAC-1
will remain energized for an additional 90 seconds.
1225
Jumper Y1 to DHUM to reduce the cooling off-delay to 5
1750
seconds. (See Fig. 1.)
2100
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.)
1400
The thermostat closes the R to G-and-Y1 circuits for low-
2000
cooling or closes the R to G-and-Y1-and-Y2 circuits for
2100 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.
- 5 -
terminal and switch the
Subsequent selection is
The R to Y1 circuit starts the
The outdoor unit stops, and the furnace