Bryant 66120 Installation, Start-Up, Operating And Service And Maintenance Instructions page 87

BLWM on cooling airflow. Cooling airflow is based on the
A/C selection shown in Fig. 64. 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. 38.
b. Single- -Stage Thermostat and Two- -Speed Cooling
(Adaptive Mode) - -
See Fig. 38 and 39 for thermostat connections.
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.
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. 38. When ACRDJ is 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
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 furnace blower motor BLWM at low- -cooling airflow which is
the true on- -board CF selection as shown in Fig. 64.
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 Fig. 38.
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. 38.
c. Two- -Stage Thermostat and Two- -Speed Cooling
See Fig. 38 and 39 for thermostat connections
NOTE: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. See Fig. 38.
for cooling", closing the
The thermostat closes the
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 (continuous fan) selection as shown in Fig. 65.
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
High- -cooling airflow is based on the A/C (air conditioning)
selection shown in Fig. 64.
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. 38.
4. Dehumidification Mode
See Fig. 38 and 39 for thermostat connections.
The dehumidification output, D or DHUM on the Ther-
midistat should be connected to the furnace control thermo-
stat 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 removed for more than 48 hours, the furnace control
reverts back to non- -dehumidification mode.
The cooling operation described in item 3 above also
applies to operation with a dehumidification 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 low
cooling airflow demand is reduced by 10 percent.
b. High cooling- -When the R- -to- -G- -and Y/Y2 circuit is
closed and there is a demand for dehumidification, high
cooling airflow demand is reduced by 10 percent.
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
airflow. Continuous blower airflow selection is initially
based on the CF (continuous fan) selection shown in Fig.
64. Factory default is shown in Fig. 64. Terminal EAC- -1 is
energized as long as the blower motor BLWM is energized.
During a call for heat, the furnace control CPU will trans-
ition the blower motor BLWM to continuous blower airflow
or low- -heat 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 low- -heat, and 25 seconds in high- -heat),
allowing the furnace heat exchangers 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
87
R- -to- -G- -and- -Y1 circuits for
at high- -cooling airflow.