10
S8XB-SF-2B-EN
NNoottee:: If PS2 does not close within the 45 seconds, the
IFC will wait 10 minutes and repeat steps 3 & 4. If
on the third attempt during the same heating call,
PS2 does not close within the 45 second proving
time, the unit will run in 1
st
stage until the
thermostat R-W2 contacts open.
5. When the temperature raises enough to satisfy the
thermostat setting, contacts R-W2 will open, the 2
nd
stage gas valve will close, the indoor blower motor
will ramp down to 1
st
stage, and the unit will
continue to run until R-W1 contacts open.
6. When the temperature raises enough to satisfy the
thermostat setting, contacts R-W1 will open.
7. The gas valve relay will open, closing the gas valve.
The inducer will continue to run for approximately 5
seconds to remove any combustion byproducts
from inside the furnace.
8. The indoor blower continues to run to remove heat
from the heat exchangers. This blower off time is
field adjustable through the IFC menu setup option.
The seven-segment LED will read 1DL = Idle, no
thermostat demand.
SSiinnggllee SSttaaggee CCoooolliinngg
1. R-Y1-G contacts on the thermostat close sending
24VAC to the Y1 and G low voltage terminals on the
IFC. Technician should read 24VAC between Y1-B/C
and between G-B/C.
NNoottee:: For S8X2 units, the factory supplied Y1-O
jumper must remain in place for proper
seven-segment LED readout, and furnace
operation. If removed, the seven-segment
LED will read “
HP1
”.
2. 24VAC is sent to the OD unit via thermostat wiring.
3. The indoor blower ramps to the cooling airflow.
The seven-segment LED for example will
alternately read:
• CL1 = Cooling, Stage 1 (S8X2)
• CP1 = Cooling, Stage 1 (S8B1/S8X1)
• tP3 = Tap 3
4. When the temperature is lowered enough to satisfy
the thermostat setting, contacts R-Y-G will open.
5. The OD unit shuts off and the indoor blower shuts
off, unless a blower “Cool Off Delay” has been
enabled in the IFC setup menu options. The seven-
segment LED will read “IDL” = Idle, no thermostat
demand.
TTwwoo SSttaaggee CCoooolliinngg
1. See sequence of operation for Single stage cooling
operation above (steps 1–3)
2. R-Y2 contact on the thermostat close sending
24VAC to Y2 low voltage terminal on the IFC.
Technician should read 24VAC between Y2 and B/C.
3. 24VAC is sent to the OD unit via thermostat wiring.
4. The indoor airflow ramps to 2
nd
stage airflow. The
seven-segment LED for example will read:
• CL2 = Cooling, Stage 2 (S8X2)
• CP2 = Cooling, Stage 2 (S8X1)
• tP7 = Tap 7
5. When the temperature is lowered enough to satisfy
the thermostat setting, contacts R-Y1-Y2-G will
open.
6. The OD unit shuts off and the indoor blower shuts
off, unless a blower “Cool Off Delay” has been
enabled in the IFC setup menu options. The seven-
segment LED will read 1DL = Idle, no thermostat
demand.
SSiinnggllee SSttaaggee HHeeaatt PPuummpp
1. R-Y1-G contacts on the thermostat close sending
24VAC to the Y1 and G low voltage terminals on the
IFC. Technician should read 24VAC between Y1-B/C
and between G-B/C.
NNoottee:: For S8X2 units, the factory supplied Y1-O
jumper must be removed for proper
seven-segment LED readout and furnace
operation during defrost. If left in place,
the seven-segment LED will read
CL1
2. 24 VAC is sent to the OD unit via thermostat wiring.
3. The indoor blower ramps to the cooling airflow.
The seven-segment LED for example will
alternately read:
• HP1 = Cooling, Stage 1 (S8X2)
• CP1 = Cooling, Stage 1 (S8B1/S8X1)
• tP3 = Tap 3
4. When the temperature is lowered enough to satisfy
the thermostat setting, contacts R-Y-G will open.
5. The OD unit shuts off and the indoor blower shuts
off, unless a “Cool Off Delay” has been enabled in
the IFC setup menu options. The seven-segment
LED will read 1DL = Idle, no thermostat demand.
TTwwoo SSttaaggee HHeeaatt PPuummpp
1. See sequence of operation for single stage cooling
operations above (steps 1–3).
2. R-Y2 contact on the thermostat close sending
24VAC to Y2 low voltage terminal on the IFC.
Technician should read 24VAC between Y2 and B/C.
3. 24VAC is sent to the OD unit via thermostat wiring.
4. The indoor airflow ramps to 2
nd
stage airflow. The
seven-segment LED for example will read:
• HP2 = Cooling, Stage 2 (S8X2)
• CP2 = Cooling, Stage 2 (S8X1)
• tP7 = Tap 7
5. When the temperature is raised enough to satisfy
the thermostat setting, contacts R-Y1-Y2-G will
open.
6. The OD unit shuts off and the indoor blower shuts
off, unless a “Blower Off Delay” has been enabled
in the IFC setup menu options. The seven-segment
LED will read 1dL = Idle, no thermostat demand.
SSeeqquueennccee ooff OOppeerraattiioonn SS88BB11//SS88XX11//SS88XX22
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