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4.
Dehumidification Mode
See Fig. 35 and 36 for thermostat connections.
The dehumidification output, D or DHUM on the Ther-
midistat should be connected to the furnace control thermo-
stat terminal DHUM. When there is a dehumidify demand,
the DHUM input is activated, which means 24 vac signal is
removed from the DHUM input terminal. In other words,
the DHUM input logic is reversed. The DHUM input is
turned ON when no dehumidify demand exists. Once 24
vac is detected by the furnace control on the DHUM input,
dehumidification capability is activated. If the DHUM input
is removed for more than 48 hours, the furnace control
reverts back to non--dehumidification mode.
The cooling operation described in item 3 above also
applies to operation with a dehumidification thermostat .
The exceptions are listed below:
a.
Low cooling
--When the R--to--G--and--Y1 circuit is closed
and there is a demand for dehumidification, the low
cooling airflow demand is reduced by 10 percent.
b.
High cooling
--When the R--to--G--and Y/Y2 circuit is
closed and there is a demand for dehumidification, high
cooling airflow demand is reduced by 10 percent.
c.
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.
5.
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 (continuous fan) selection shown in Fig.
58. Factory default is shown in Fig. 58. Terminal EAC--1 is
energized as long as the blower motor BLWM is energized.
During a call for heat, the furnace control CPU will trans-
ition the blower motor BLWM to continuous blower airflow
or low--heat 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 (45
seconds in low--heat, and 25 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 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 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 opera-
tion.
Continuous Blower Speed Selection from Thermostat
To
select different continuous--blower airflow 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. 58. 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. 58. The
selection can be changed as many times as desired and is
stored in the memory to be automatically used following a
power interruption.
NOTE
: If the blower--off delay is set to the maximum, the
adjustable continuous--fan feature is locked (i.e., fan speed cannot
be changed from its current setting).
6.
Heat pump
See Fig. 35 and 36 for thermostat connections.
When installed with a heat pump, the furnace control auto-
matically 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 or low--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 disap-
pear 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.
7.
Component self--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.
35.) Refer to Page 77 for instructions.
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