Sequence Of Operation - Trane UHMB060ACV3VA Installer's Manual

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 comfort 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
furnace 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 moving 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
communicating comfort control (ERR 22) and
User Interface (RETRY LO). The Red alert LED
two times repeatedly.
10. If a flame is detected, the IFC will start the heat
exchanger 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 and 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 motor to ramp up or down.
18-CD30D1-9
Installer's Guide
14. With a heat demand less than 65% from the
communicating comfort control, the IFC signals
the variable speed inducer motor drive board to
ramp down to that corresponding demand speed.
The reduction of the vent motor speed in steps
allows the gas flow through the gas valve to also
be reduced in steps, decreasing the chance of
burner flame out. The minimum capacity change
is 1%.
15. The minimum capacity of all furnaces is 40%,
with the exception of the *UHMC120. The
minimum capacity for this furnace is 45%.
16. The communicating comfort control will continue
to call for the requested capacity demand until the
indoor temperature is back at the set point OR,
17. If the communicating comfort control does not
detect that the indoor temperature is moving
back towards its set point or the indoor
temperature is still moving away from the set
point, it will signal the IFC to go to a higher
capacity of heat.
18. The IFC then signals the variable speed inducer
drive to ramp up the vent motor in steps. As the
vent motor speed increases the amount of gas
coming through the gas valve will increase. The
IFC will also increase the indoor blower motor
speed.
19. The communicating comfort control will continue
to monitor the indoor temperature and send
signals to the IFC to modulate the heating
capacity or turn off to maintain the homeowner's
set point.
20. Once the communicating comfort control senses
that the heating requirements have been
satisfied, the gas valve will be de-energized and
gas flow will cease. The variable speed vent motor
will de-energize approximately after a 5 second
post purge. All pressure switches will open and
the indoor blower motor will then run the heat off
delay that is selected in the User Interface menu.
Indoor Blower motor operation thermostat fan
switch "ON" (Communicating Mode)
The communicating comfort control signals a continu-
ous fan call. The factory setting is 50% of the cooling
cfm selected but can be adjusted from 25% - 100%
through the Installer Setup menu on the communi-
cating comfort control. If the outdoor unit is a 2 stage
system, the factory setting is 50% of the 2nd stage
cooling cfm. If the outdoor unit is a 24 volt single
stage cooling system, the factory setting is 50% of the
cooling cfm.
NOTE: If the actual relative humidity (RH) is at
or below the set-point, the fan will run until the
continuous fan call is removed or the actual RH
exceeds the set-point. If the actual RH is above
the set-point, the fan will not turn on.
See the communicating comfort control Installer's
Guide for additional information.
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