58
the furnace blower motor BLWM transitions to run at
high-- cooling airflow.
The electronic air cleaner terminal EAC--1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R--to--G--and--Y circuit are
opened. The outdoor unit stops, and the furnace blower BLWM
and electronic air cleaner terminal EAC--1 will remain energized
for an additional 90 seconds. Jumper Y1 to DHUM to reduce the
cooling off-- delay to 5 seconds. (See Fig. 27.)
c. Two--Stage Thermostat and T wo--Speed Cooling
See Fig. 34 for thermostat connections
NOTE: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. (See Fig. 27.)
The thermostat closes the R--to--G--and--Y1 circuits for
low--cooling or closes the R--to--G--and--Y1--and--Y2 circuits for
high--cooling. The R --to --Y1 circuit starts the outdoor unit on
low--cooling speed, and the R--to--G--and--Y1 circuit starts the
furnace blower motor BLWM at low-- cooling airflow which is the
true on -- board CF (continuous fan) selection as shown in Fig. 61.
The R--to-- Y1 --and --Y2 circuits start the outdoor unit on
high-- cooling speed, and the R -- to-- G-- and--Y/Y2 circuits start the
furnace blower motor BLWM at high--cooling airflow .
High-- cooling airflow is based on the A/C (air conditioning)
selectionshowninFig.63.
The electronic air cleaner terminal EAC--1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R--to--G--and--Y1 or R--to--
G--and --Y1--and--Y2 circuits are opened. The outdoor unit stops,
and the furnace blower BLWM and electronic air cleaner terminal
EAC--1 will remain energized for an additional 90 seconds.
Jumper Y1 to DHUM to reduce the cooling off --delay to 5
seconds. (See Fig. 27.)
4. Thermidistat Mode
See Fig. 28-- 30 for thermostat connections.
The dehumidification o utput, DHUM on the Thermidistat
should be connected to the furnace control thermostat
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,
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
applies to operation with a Thermidistat. The exceptions
are listed below:
a. Low c ooling-- 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. 61.
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) selection shown in Fig. 61.
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
furnace control is in the Thermidistat mode an d there is a
demand for dehumidification. The cooling operation
described 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
dehumidification is satisfied. Low--cooling airflow is
the true on--board CF (continuous fan) selection as
shown in Fig. 63.
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
dehumidification is satisfied. High--cooling airflow is
based on the A/C (air conditioning) selection shown in
Fig. 63.
c. When the “call for cooling” is satisfied and there is a
demand for dehumidification, the cooling blower--of f
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.
63. Factory default is shown in Fig. 63. 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 midrange 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 operation.
Continuous Blower Speed Selection from Thermostat
To select different continuous-- blower airflows from the
room thermostat, momentarily turn off the FAN switch or
pushbutton on the room thermostat for 1--3 seconds after
the blower motor BLWM is operating. The furnace control
315A
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