Bryant Bruant 4 Way Gas 355AAV - Manual (Page 48)

48
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. 37.) 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 furnace blower
motor BLWM at low--cooling airflow which is the true on--board
CF selection as shown in Fig. 47.
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 highcooling airflow.
High--cooling airflow is based on the A/C selection shown in Fig.
47.
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. 37.)
3. Two--Stage Thermostat and Two--Speed Cooling
(See Fig. 57 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. 37.)
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 on low--cooling airflow which is the true on--board CF
selection as shown in Fig. 47. 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 Fig. 47.
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. 37.)
THERMIDISTAT MODE
See Fig. 51--54 for Thermidistat connections.
The dehumidification output, DHUM on the Thermidistat 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--Thermidistat mode.
The cooling operation described in item 3. above applies to
operation with a Thermidistat. 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 true on--board CF
selection as shown in Fig. 47.
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. 47.
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 Thermidistat mode and there is a demand for
dehumidification. The cooling operation described in Item 3.
above also applies to operation with a Thermidistat. The exceptions
are listed below:
a. 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 airflow 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--cooling airflow is the
true on--board CF selection as shown in Fig. 47.
b. High cooling--When the R to Y/Y2 cicuit is closed, R
to G circuit is open, and there is a demand for
dehumidifiation, the furnace blower motor BLWM will
drop the blower 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. 47.
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.
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
selection shown in Fig. 47. Factory default is shown in Fig. 47.
Terminal EAC--1 is energized as long as the blower motor BLWM
is energized.
During a call for heat, the blower BLWM will transition the blower
motor BLWM to continuous blower airflow, low--heat airflow, or
the mid--range airflow, whichever is lowest. The blower motor
OFF and remain OFF for the blower--ON delay (60 seconds in
low--heat and 35 seconds in high--heat) allowing the furnace heat
355A