Trane UHMB060ACV3VA Installer's Manual page 45

17. PS1 and PS2 close.
18. The IFC receives a 24 VAC signal from PS1 and
PS2 when they close. This verifies the vent
motor is moving the correct amount of
combustion air through the furnace and the vent
system.
19. IFC starts the hot surface ignitor learning
routine warm-up time cycle.
20. IFC turns on the gas valve. Trial time for
ignition is 5 seconds.
21. The IFC verifies ignition by the flame current
sensing method. If a flame is not detected, the
IFC will cycle the furnace three times to try and
verify a flame. If no flame is detected, the IFC
will lockout for one hour. The IFC will send an
alert code to the communicating comfort control
(ERR 22) and User Interface (RETRY LO) as well
as flash its Red alert LED two times repeatedly.
22. If a flame is detected, the IFC will start the heat
exchanger warm-up time delay for the indoor
blower.
23. "IGNITION" will now be displayed in the
"STATUS" section of the User Interface menu.
24. After 45 seconds, the IFC signals the indoor
blower motor to run at the programmed ignition
sequence speed.
25. Every 1 minute, the IFC will signal the vent
motor to ramp up. The increase of the vent
motor speed allows the gas flow through the gas
valve to also be increased in 3% steps. This 3%
increase will be repeated every 1 minute until
the capacity requested is 100%. Pressure switch 3
closes at approximately 95% of capacity.
26. The IFC will also increase the indoor blower
motor speed in appropriate steps.
Indoor Blower motor operation thermostat fan
switch "CONTINUOUS" (24V Mode)
R and G comfort control contacts close signaling a
continuous fan call. The continuous fan cfm is field
selectable and can be adjusted through the User
Interface menu. The factory setting is 50% of the
cooling cfm selected but can be set at 25%, 50%, 75%,
or 100%. If the system has a 2 stage outdoor unit, the
setting is 50% of the 2nd stage cooling cfm.
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Communicating
Comfort Control
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