51
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 the Thermidistat mode and there is a demand for
dehumidification. The cooling operation described in item 4. above
also applies to operation with a Thermidistat. The exceptions are
listed below:
1.
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.
2.
High cooling
– When the R to Y/Y2 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 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.
3.
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 furnace control CPU will transition the
blower motor BLWM to continuous blower airflow, low--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 the blower--ON delay (60 seconds in
medium heat, and 35 seconds in high--heat), allowing the furnace
heat exchangers to heat up more quickly, then restarts at the end of
the blower--ON delay period at low--heat, medium--heat, or
high--heat airflow respectively.
The blower motor BLWM will revert to continuous--blower
airflow after the heating cycle is completed. In high--heat, the
furnace control CPU will drop the blower motor BLWM to
low--heat airflow during the selected blower--OFF delay period
before transitioning to continuous--blower airflow.
When the thermostat “calls for low--cooling”, the blower motor
BLWM will 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.
Continuous Blower Speed Selection from Thermostat
To select different continuous--blower airflows from the room
thermostat, momentarily turn off the FAN switch or push button on
the room thermostat for 1--3 seconds after the blower motor
BLWM is operating. The furnace control CPU will shift the
continuous--blower airflow from the factory setting to the next
highest CF selection airflow as shown in Fig. 47. Momentarily
turning off the FAN switch again at the thermostat 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 Fig. 47. The
selection can be changed as many times as desired and is stored in
the memory to be automatically used following a power
interruption.
Heat Pump
See Fig. 54--57 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, low--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
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.
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 Fig. 33)
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 3.
2. After waiting 15 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 mid--range airflow for 15 seconds, then OFF.
4. After shutting the blower motor BLWM OFF the furnace
control CPU shuts the inducer motor IDM OFF.
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.
58MV
C
