UHM-DHM-SF-1H
15
Service Facts
IFC INDUCER LEARNING ROUTINE SEQUENCE
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
•
The furnace IFC will go through an inducer learn-
ing routine for three pressure switches.
•
The learning routine is done to determine the
correct amount of ventilation air for complete
combustion.
•
The inducer motor speed may be different for each
installation due to the different length and size of
the ventilation pipe, exhaust vent pipe, number
of pipe fittings used, and the type of vent cap
installed.
•
The inducer learning routine is repeated each time
the power to the furnace is interrupted. Once
power is restored and the furnace receives a call
for heat, the PS-1, PS-2 inducer learning routine
will be initiated. The furnace IFC will not go
through a PS-3 inducer learning routine until it
receives a call for 100% (high) heat.
•
To ensure the furnace heating efficiency is main-
tained the furnace IFC will repeat the inducer
motor learning routine after :
150 Cycles at 40% (low) heat
100 Cycles at 65% (medium) heat
50 Cycles at 100% (high) heat
PS-1, PS-2 Inducer Learning Routine
•
The furnace IFC checks the pressure switches PS-
1, PS-2 and PS-3. They all have to be open before
a heating cycle can begin.
•
The furnace IFC sends a digital signal to the
variable speed inducer drive to run the inducer
motor at the preset factory 65% (medium) heat
RPM.
•
The furnace IFC waits for the PS-1 and PS-2
pressure switches to close. A 24 Volt AC signal is
sent to the furnace IFC when a pressure switch
closes.
•
If PS-1 and PS-2 do not close at the preset factory
65% (medium) heat RPM, the furnace IFC will
continue to signal the variable speed inducer
drive to increase the inducer speed in steps until
PS-1 and PS-2 close or until the maximum RPM
for 65% (medium) heat is reached.
•
When PS-1 and PS-2 switches close, the furnace
IFC will then start the ignition cycle.
•
The IFC now starts the igniter warm up cycle.
•
Near the end of the warm up cycle the furnace
IFC will turn on the gas valve.
NOTE: The furnace lights at approximately
65% of capacity.
•
When the burner flame is detected by the
furnace IFC, a forty-five second time delay
for indoor blower operation begins. The
forty-five second time delay allows the heat
exchanger and the recuperative cell to
warm up.
•
The furnace IFC will now start its 65% (me-
dium) heat inducer learning routine.
•
The furnace IFC will signal the variable
speed inducer drive beginning to reduce
the inducer motor speed in steps until the
furnace IFC detects that PS-2 is open.
•
When PS-2 opens, the furnace IFC will
NOTE the inducer motor RPM.
•
The furnace IFC then adds an additional
number of RPM to the 65% (medium) heat
inducer motor NOTED RPM until PS-2
closes.
•
The additional number of RPM plus this
NOTED RPM is the learned 65% (medium)
heat inducer operating RPM.
•
The furnace IFC now stores this learned op-
erating inducer RPM for 65% (medium)
heat in its memory.
•
The furnace IFC will use this stored learned
operating inducer RPM for 65% (medium)
heat calls it receives in the future.
•
If the furnace IFC is still receiving a call for
low heat operation it will now start the
learning routine for 40% (low) heat.
•
The furnace IFC will then continue to re-
duce the inducer motor RPM in steps until
the furnace IFC detects that PS-1 is open.
•
When PS-1 opens, the furnace IFC will
NOTE the inducer motor RPM.
•
The furnace IFC then adds an additional
number of RPM to the 40% (low) heat in-
ducer motor NOTED RPM until PS-1
closes.
•
The additional number of RPM plus this
NOTED RPM is the learned 40% (low) heat
inducer operating RPM.
•
The furnace IFC now stores this learned in-
ducer operating RPM for 40% (low) heat in
its memory.
•
The furnace IFC will use this stored learned
inducer operating RPM for 40% (low) heat
calls it receives in the future.
•
Whenever the furnace is powered up or af-
ter a RESET, the furnace IFC will not go
through a learning routine for 100% (high)
heat until it receives a call for 100% (high)
heat.
Summary of Contents for ADHMB060BCV3VA
Page 37: ...UHM DHM SF 1H 37 Service Facts...
Page 39: ...UHM DHM SF 1H 39 Service Facts...
Page 41: ...UHM DHM SF 1H 41 Service Facts...
Page 47: ...UHM DHM SF 1H 47 Service Facts...
Page 49: ...UHM DHM SF 1H 49 Service Facts...
Page 51: ...UHM DHM SF 1H 51 Service Facts...
