935CA: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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high-cooling. If starting up in low-cooling, the furnace control CPU
determines the low-cooling on-time (from 0 to 20 minutes) which is
permitted before switching to high-cooling. If the power is interrupted,
the stored history is erased and the furnace control CPU will select
low-cooling for up to 20 minutes and then energize the air conditioning
relay ACR to energize the Y/Y2 terminal and switch the outdoor unit to
high-cooling, as long as the thermostat continues to call for cooling.
Subsequent selection is based on stored history of the thermostat cycle
times.
The wall thermostat “calls for cooling”, closing the R-to-G-and-Y
circuits. The R-to-Y1 circuit starts the outdoor unit on low-cooling
speed, and the R-to-G-and-Y1 circuits starts the furnace blower motor
BLWM at low-cooling airflow which is the true on-board CF selection
as shown in
Fig. 42
.
If the furnace control CPU switches from low-cooling to high-cooling,
the furnace control CPU will energize the air conditioning relay ACR.
When the air conditioning relay ACR is energized the R-to-Y1-and-Y2
circuits switch the outdoor unit to high-cooling speed, and the
R-to-G-and-Y1-and-Y/Y2 circuits transition the furnace blower motor
BLWM to high-cooling airflow. High-cooling airflow is based on the
A/C selection shown in
Fig. 42
.
NOTE:
When transitioning from low-cooling to high-cooling the
outdoor unit compressor will shut down for 1 minute while 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 sec.
Jumper Y1 to DHUM to reduce the cooling off-delay to 5 sec. See
Fig. 42
.
c.
Two-Stage Thermostat and Two-Speed Cooling
See
Fig. 42
and thermostat wiring for connections
NOTE:
The air conditioning relay disable jumper ACRDJ must be
disconnected to allow thermostat control of the outdoor unit staging. See
Fig. 42
.
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. 65
. 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) selection
shown in
Fig. 65
.
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 sec. Jumper Y1 to DHUM to
reduce the cooling off-delay to 5 sec. See
Fig. 42
.
3.
Dehumidification Mode
See
Fig. 42
and thermostat wiring for connections.
The dehumidification output, D or DHUM on the Thermostat
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 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 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. 65
.
b.
High cooling
-When the R-to-G-and Y/Y2 circuit is 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. 65
.
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 sec to 5 sec.
4.
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 3 above
also applies to operation with a dehumidification thermostat. 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. 65
.
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. 65
.
c. When the “call for cooling” is satisfied and there is a demand for
dehumidification, the cooling blower-off delay is decreased from
90 sec to 5 sec.
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. 65
. Factory default is
shown in
Fig. 65
. 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 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 (25 sec in heat), allowing the
furnace heat exchangers to heat up more quickly, then restarts at the
end of the blower-ON delay period at heat airflow.
The blower motor BLWM will revert to continuous-blower airflow
after the heating cycle is completed. In heat the furnace control
CPU will drop the blower motor BLWM to 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 sec at low-cooling airflow before transitioning back to
continuous-blower airflow.
When the thermostat “calls for high-cooling”, the blower motor
