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the continuous-blower airflow from the factory setting to the
next highest CF selection airflow as shown in Table 1 and 1a.
Momentarily turning off the FAN switch again at the thermo-
stat will shift the continuous-blower airflow up one more
increment. If you repeat this procedure enough you will
eventually shift the continuous-blower airflow to the lowest CF
selection as shown in Table 1 and 1a. The selection can be
changed as many times as desired and is stored in the memory
to be automatically used following a power interruption.
Step 7—Heat Pump Defrost
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, low-heat airflow, or
the midrange 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 low-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 blower airflow.
Step 8—Component Test
The furnace features a component test system to help diagnose 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 Appendix A.)
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:
1. The furnace control CPU turns the inducer motor IDM ON at
medium speed and keeps it ON through step c.
2. After waiting 10 seconds the furnace control CPU turns the
hot surface igniter ON for 15 seconds, then OFF.
3. The furnace control CPU then turns the blower motor BLWM
on at midrange airflow for 15 seconds, then OFF.
4. After shutting the blower motor OFF the furnace control CPU
shuts the inducer motor IDM.
NOTE: The EAC terminals are energized when the blower is
operating.
After the component test is completed, 1 or more status codes (11,
25, 41, or 42) will flash. See Service Label on blower access panel
or Service/Status Code Instructions for explanation of status codes.
NOTE: To repeat component test, turn setup switch SW1-6 to
OFF and then back ON.
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