116
S9V2-VS-SVX001-1C-EN
7. When the temperature is lowered enough to satisfy
the thermostat setting, contacts R-Y1-Y2-G will
open.
8. 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 “IDL” = Idle, no thermostat demand.
VVaarriiaabbllee SSppeeeedd IInndduucceerr LLeeaarrnniinngg RRoouuttiinnee
The purpose of the learning routine is to determine the
most efficient inducer operating speed for the furnace
in a given heat stage. On a call for gas heat, or
transition to a given gas heat stage, the inducer is
commanded to a speed in order to close the pressure
switch for that stage.
NNoottee:: NOTE: Gas manifold measurements or
adjustments must not be made until the learning
routine for each stage has been successfully
completed.
There are two learning routines, one for 1
st
stage gas
heat and another for 2
nd
stage gas heat. Each learning
routine is separate and will occur:
1. Upon initial commissioning of the furnace
2. When power to the furnace has been interrupted
3. After the below number of heating cycles has been
reached
a. 150 1
st
stage cycles
b. 100 2
nd
stage cycles
11
sstt
SSttaaggee HHeeaatt
1. When 1
st
stage gas heat is requested, the variable
speed inducer is energized and will run at the
predetermined factory default 1
st
stage inducer
speed. Once the ignition process and the blower on
delay have successfully completed the IFC will
begin the Inducer Learning Routine as outlined
below
PPSS11 cclloosseess aatt ddeeffaauulltt ssppeeeedd
a. The inducer speed is reduced every 2 seconds
until PS1 opens
b. At the time PS1 opens, the IFC stores the
inducer RPM
c. The inducer RPM is then raised every 3 seconds
to re-close PS1. Upon PS1 closing, the IFC has
now learned the most efficient inducer speed for
1
st
stage gas heat operation.
PPSS11 ddooeess nnoott cclloossee aatt ddeeffaauulltt ssppeeeedd
The IFC will increase the speed of the inducer until:
a. The maximum RPM for 1
st
stage gas heat is
reached
b. Or PS1 closes
Once PS1 closes, the learning routine will begin
as stated above.
22
nndd
SSttaaggee HHeeaatt
1. When 2
nd
stage gas heat is requested, the variable
speed inducer will run at the predetermined factory
default 2
nd
stage inducer speed.
PPSS22 cclloosseess aatt ddeeffaauulltt ssppeeeedd
a. The inducer speed is reduced every 2 seconds
until PS2 opens
b. At the time PS2 opens, the IFC stores the
inducer RPM
c. The inducer RPM is then raised every 3 seconds
to re-close PS2. Upon PS2 closing, the IFC has
now learned the most efficient inducer speed for
2
nd
stage gas heat operation.
PPSS22 ddooeess nnoott cclloossee aatt ddeeffaauulltt ssppeeeedd
The IFC will increase the speed of the inducer until:
a. The maximum RPM for 2
nd
stage gas heat is
reached
b. Or PS2 closes
Once PS2 closes, the learning routine will begin
as stated above. If PS2 does not close after
reaching the maximum RPM, a PS2 open error
will be reported and the furnace will continue to
run in 1
st
stage for 10 minutes and retry 2
nd
stage. This process will repeat until the request
for 2
nd
stage heat is removed.
SSeeqquueennccee ooff OOppeerraattiioonn
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