Specifications are subject to change without notice.
42
441 01 4200 01
seconds, if no other function requires blower motor
BLWM operation.
6.
Heat pump
See Fig. 27 -- 28 for thermostat connections.
When installed with a heat pump, the furnace control auto-
matically changes the timing sequence to avoid long blow-
er 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 mo-
tor BLWM at cooling airflow, 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 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 air-
flow. 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 blow-
er motor BLWM will remain on heat airflow for the select-
ed 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 blower airflow.
7.
Component test
The furnace features a component test system to help diag-
nose a system problem in the case of a component failure.
To initiate the component test procedure, ensure that there
are no thermostat inputs to the control and all time delays
have expired. Turn on setup switch SW1--6. (See Fig. 23)
NOTE
: The component test feature will not operate if the control
is receiving any thermostat signals or until all time delays have
expired.
The component test sequence is as follows:
a. The furnace control CPU turns the inducer motor ON
at 50% torque and keeps it ON through step c.
b. After waiting for 15 seconds of inducer only
operation, the furnace control CPU turns the hot
surface ignitor ON for 15 seconds, then OFF.
c. The furnace control CPU then turns the blower motor
BLWM on at mid--range airflow for 15 seconds, then
OFF.
d. After shutting the blower motor OFF the furnace
control CPU switches the inducer OFF
.
NOTE
: The EAC terminals are energized when the blower is
operating.
After the component test is completed, 1 or more status codes
(heartbeat, 2+5, 4+1 or 4+2) will flash. See component test
section or Service Label (Fig. 36) for explanation of status codes.
NOTE
: To repeat component test, turn setup switch SW1--6 to
OFF and then back ON.
Wiring Diagrams
Refer to Fig. 43 for wiring diagram.
Troubleshooting
Refer to the service label. (Fig. 36), and wiring diagram (Fig. 43)
can be a useful tool in isolating furnace operation problems. The
Guide will help to identify the problem or failed component.
After replacing any component, verify correct operation
sequence.
