Bryant 926SB - Page 70

926SB: Installation, Start-up, Operating, Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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When the thermostat “calls for low-cooling”, the blower motor
BLWM will switch to operate at low-cooling airflow. When the
thermostat is satisfied, the blower motor BLWM will operate an
additional 90 seconds at low-cooling airflow before transitioning
back to continuous-blower airflow.
When the thermostat “calls for high-cooling”, the blower motor
BLWM will operate at high cooling airflow. When the thermostat is
satisfied, the blower motor BLWM will operate an additional 90
seconds at high-cooling airflow before transitioning back to
continuous-blower airflow. When the R-to-G circuit is opened, the
blower motor BLWM will continue operating for an additional 5
seconds, if no other function requires blower motor BLWM
operation.
The primary continuous fan airflow (CFn) can be selected using the
3-digit display/pushbuttons or via the service tech app. Refer to the
FURNACE CONTROL PROGRAMMING AND NAVIGATION
section of this manual for instructions on adjusting the continuous fan
speed via the control board interface. Alternate continuous fan airflows,
(CF2 and CF3), can only be modified via the service tech app.
Setting Active Continuous Fan Speed
Method 1: If the G input (or FAN switch/setting at the thermostat) is
turned OFF for 1 to 3 seconds and then back ON, the active continuous
fan speed will cycle to the next speed (CFnCF2). Repeating will
change the active continuous fan speed to the next speed (CF2CF3).
Repeating again will set the active continuous fan back to the primary
speed (CFn). This method is intended as a way for home owners to
adjust the continuous fan speed setting from the thermostat depending on
their needs.
Method 2: The active continuous fan speed (CFn, CF2 or CF3) can be
selected via the service tech app.
5. Heat pump
See Fig. 39 for thermostat connections.
When installed with a heat pump, the furnace control automatically
changes the timing sequence to avoid long blower off times during
demand defrost cycles. Whenever W is energized along with Y1 or
Y/Y2, the furnace control CPU will transition to or bring on the
blower motor BLWM at cooling airflow or heat airflow whichever
is lowest. The blower motor BLWM will remain on until the main
burners ignite then shut OFF and remain OFF for 25 seconds before
coming back on at heating airflow. When the W/W1 input signal
disappears, the furnace control begins a normal inducer post-purge
period while changing the blower airflow. If Y/Y2 input is still
energized the furnace control CPU will transition the blower motor
BLWM airflow to cooling airflow. If Y/Y2 input signal disappears
and the Y1 input is still energized the furnace control CPU will
transition the blower motor BLWM to low-cooling airflow. If both
the Y1 and Y/Y2 signals disappear at the same time, the blower
motor BLWM will remain on at heat airflow for the selected
blower-OFF delay period. At the end of the blower-OFF delay, the
blower motor BLWM will shut OFF unless G is still energized, in
which case the blower motor BLWM will operate at continuous fan
airflow.
Wiring Diagram
Refer to Fig. 61 for wiring diagram.
Troubleshooting
Refer to the service label (see Fig. 60). The Troubleshooting Guide (see
Fig. 71) can be a useful tool in isolating furnace operation problems.
Beginning with the word “Start,” answer each question and follow the
appropriate arrow to the next item. The Guide will help to identify the
problem or failed component. After replacing any component, verify
correct operation sequence.