Instruction manual

83
Heat Pump
See Fig. 34 and 35 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/W1 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, minimum-heat airflow, or the mid-range
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 modulating heat
airflow. When the W/W1 input signal disappears, the furnace
cont ro l 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 minimum-heat airflow for the selected blower-OFF
delay period. At the end of the blower-OFF delay, the blower
motor BL WM will shut OFF unless G is still energized, in which
case the blower motor BLWM will operate at continuous blower
airflow.
Component Self Test
Refer to page 6 8 for instructions.
987MA