Installation Manual

441 01 3500 00 55
Specifications are subject to change without notice.
should be connected to the furnace control thermostat ter-
minal DHUM. When there is a d ehumidify d emand, 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 o n the DHUM input,
the furnace control operates in Thermidistat mode. If the
DHUM input is low for more than 48 hours, the furnace
control reverts back to non--Thermidistat mode.
The cooling operation described in item 3. above also ap-
plies to operation with a Thermidistat. The exceptions are
listed below:
a. Low cooling-- W h e n t h e R -- t o -- G -- a n d -- Y 1 c i r c u i t i s
closed and there is a demand for dehumidification, the
furnace blower motor BLWM will drop the blower
airflow to 86 percent of low -- cooling airflow which is
the true on --board CF (continuous fan) selection as
shown in Fig. 53.
b. High cooling-- W h e n t h e R -- t o -- G -- a n d Y / Y 2 c i r c u i t i s
closed and there is a demand for dehumidification, the
furnace blower motor BLWM will drop the blower
airflow to 86 percent of high --cooling airflow. High--
cooling airflow is based on the A/C (air conditioning)
selectionshowninFig.53.
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. Super--Dehumidify Mode
Super--Dehumidify mode can only be entered if the fur-
nace control is in the Thermidistat mode and there is a de-
mand for dehumidification. The cooling operation de-
scribed in item 3. above also applies to operation with a
Thermidistat. The exceptions are listed below:
a. 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 percent 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 dehumidi-
fication is satisfied. Low--cooling airflow is the true
on--board CF (continuous fan) selection as shown in
Fig. 53.
b. 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 percent 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 dehumidi-
fication is satisfied. High--cooling airflow is based on
the A/C (air conditioning) selection shown in Fig. 53.
c. 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.
6. 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.
53. Factory default is shown in Fig. 53. Terminal EAC--1
is energized as long as the blower motor BLWM is ener-
gized.
During a call for heat, the furnace control CPU will transi-
tion the blower motor BLWM to continuous blower air-
flow, low-- heat airflow, or the mid --range airflow, which-
ever 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--blow-
er 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 air-
flow. When the thermostat is satisfied, the blower motor
BLWM will operate an additional 90 seconds at low-- cool-
ing airflow before transitioning back to continuous--blow-
er 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 sec-
onds, if no other function requires blower motor BLWM
operation.
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).
7. Heat pump
See Fig. 29 -- 30 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, 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 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 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.
8. 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. 26.)
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 high--heat speed and keeps it ON through step c.