Sequence Of Operation - American Standard UHMB060ACV3VB Series Service Facts

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Communicating
Comfort Control
NOTE: Y1 is output to non-communicating outdoor unit
UHM-DHM-SF-1V-EN
Service Facts

SEQUENCE OF OPERATION

SEQUENCE OF OPERATION – COMMUNICATING
MODE
1. This furnace is fully modulating between 40% and
100% of capacity in 1% increments. The furnace
always lights at approximately 65% and will modulate
up or down; depending on the communicating com-
fort control demand. Requested capacity can be seen
in the "STATUS" section of the User Interface menu.
Note:
Pressure Switch 1 closes at approximately 40%
of capacity.
Pressure Switch 2 closes at approximately 65%
of capacity.
Pressure Switch 3 closes at approximately 95%
of capacity.
2. The communicating comfort control signals the fur-
nace IFC for heat.
3. The IFC then checks all safeties, thermostats, and
pressure switches PS1, PS2, and PS3.
4. The IFC signals the variable speed inducer drive to
start the vent motor at the speed needed to close
pressure switches PS1 and PS2.
5. PS1 and PS2 close.
6. The IFC receives a 24 VAC signal from PS1 and PS2
when they close. This verifies the vent motor is mov-
ing the correct amount of combustion air through the
furnace and the vent system.
7. IFC starts the hot surface ignitor learning routine
warm-up time cycle.
8. IFC turns on the gas valve. Trial time for ignition is 5
seconds.
Note:
The furnace lights at approximately 65% of capacity.
9. 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 communicat-
ing comfort control and User Interface. The Red alert
LED two times repeatedly.
10. If a flame is detected, the IFC will start the heat ex-
changer warm-up time delay for the indoor blower.
11. "IGNITION" will now be displayed in the "STATUS"
section of the User Interface menu.
12. After 45 seconds, the IFC signals the indoor blower
motor to run at the programmed ignition sequence
speed.
13. Depending on the communicating comfort control
demand, the IFC will then signal the variable speed
inducer motor drive board and the indoor blower mo-
tor to ramp up or down.
14. With a heat demand less than 65% from the commu-
nicating comfort control, the IFC signals the variable
speed inducer motor drive board to ramp down to
that corresponding demand speed. The reduction
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