F96VTN and G96VTN: 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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2.
Two-Stage Thermostat and Two-Stage Heating
See
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
-
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
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
.
b. Two-Stage Thermostat and Two-Speed Cooling
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 CF (continuous fan) selection as shown
in
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) selection shown in
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.
4.
Dehumidify Mode
and 40 for thermostat connections.
The H output on the humidify sensing 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.
Activation/Deactivation
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, Cooling mode. above
also applies to operation with a humidity sensing 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
. Factory default is
shown in
. 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 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
operation.
6.
Heat pump
When installed with a heat pump, the furnace control automatically