F80CTL & G80CTL: 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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h. Blower-Off Delay -When the thermostat is satisfied, the R to W
circuit is opened, de-energizing the gas valve GV-M, stopping
gas flow to the burners, and de-energizing the humidifier
terminal HUM. The inducer motor IDM will remain energized
for a 5-second post-purge period. The blower motor BLWM and
air cleaner terminal EAC-1 will remain energized at low-heat
airflow or transition to low-heat airflow for 90, 120, 150, or 180
seconds (depending on selection at blower-OFF delay switches).
The furnace control CPU is factory-set for a 120-second
blower-OFF delay.
2. Two-Stage Thermostat and Two-Stage Heating
See Fig. 28 - Fig. 31 for thermostat connections.
NOTE: In this mode the low-heat only switch SW1-2 must be ON to
select the low-heat only operation mode in response to closing the
thermostat R-to-W1 circuit. Closing the thermostat R-to- W1-and-W2
circuits always causes high-heat operation, regardless of the setting of
the low-heat only switch.
The wall thermostat “calls for heat”, closing the R-to-W1 circuit for
low-heat or closing the R-to-W1-and-W2 circuits for high-heat. The
furnace control performs a self-check, verifies the low-heat and
high-heat pressure switch contacts LPS and HPS are open, and starts the
inducer motor IDM in high-speed.
The start up and shut down functions and delays described in item 1.
above apply to the 2-stage heating mode as well, except for switching
from low- to high-Heat and vice versa.
a. Switching from Low- to High-Heat - If the thermostat R-to-W1
circuit is closed and the R-to-W2 circuit closes, the furnace
control CPU will switch the inducer motor IDM speed from low
to high. The high-heat pressure switch relay HPSR is
de-energized to close the NC contact. When sufficient pressure is
available the high-heat pressure switch HPS closes, and the
high-heat gas valve solenoid GV-HI is energized. The blower
motor BLWM will transition to high-heat airflow five seconds
after the R-to-W2 circuit closes.
b. Switching from High- to Low-Heat -If the thermostat R-to- W2
circuit opens, and the R-to-W1 circuit remains closed, the
furnace control CPU will switch the inducer motor IDM speed
from high to low. The high-heat pressure switch relay HPSR is
energized to open the NC contact and de-energize the high-heat
gas valve solenoid GV-HI. When the inducer motor IDM reduces
pressure sufficiently, the high-heat pressure switch HPS will
open. The gas valve solenoid GV-M will remain energized as
long as the low-heat pressure switch LPS remains closed. The
blower motor BLWM will transition to low-heat airflow five
seconds after the R-to-W2 circuit opens.
3. Cooling mode
The thermostat “calls for cooling.”
a. Single-Speed Cooling-
See Fig. 28 for thermostat connections
The thermostat closes the R-to-G-and-Y circuits. The R-to- Y
circuit starts the outdoor unit, and the R-to-G-and-Y/Y2 circuits
start the furnace blower motor BLWM on cooling airflow.
Cooling airflow is based on the A/C selection shown in Fig. 14.
The electronic air cleaner terminal EAC-1 is energized with 115
vac when the blower motor BLWM is operating.
When the thermostat is satisfied, the R-to-G-and-Y circuits are
opened. The outdoor unit will stop, and the furnace blower motor
BLWM will continue operating at cooling airflow for an
additional 90 seconds. Jumper Y/Y2 to DHUM to reduce the
cooling off-delay to 5 seconds, see Fig. 32.
b. Two-Stage Thermostat and Two-Speed Cooling.
See Fig. 29 for thermostat connections.
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, see Fig. 14. 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, see Fig. 14.
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. 32.
4. Dehumidify Mode
See Fig. 28 - Fig. 31 for thermostat connections.
The dehumidification output, 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 operates in dehumidify mode. If the DHUM input is low for
more than 48 hours, the furnace control reverts back to
non-dehumidify mode.
The cooling operation described in item 3. above also applies to
operation with a 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,
see Fig. 14.
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, see Fig. 14.
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 Dehumidify mode and there is a demand for
dehumidification. The cooling operation described in item 3. above
also applies to operation with a 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, see Fig. 14.
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, see Fig. 14.
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
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