18-CD30D1-12
51
Installer’s Guide
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% (medium) 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
operating 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 reduce 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 inducer 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 inducer 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 after 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.
PS-3 INDUCER LEARNING ROUTINE
•
When the furnace IFC receives a digital signal for 100%
(high) heat from the comfort control it will begin the
PS-3 inducer learning routine.
•
The furnace will start the heating cycle in 65% (medium)
heat, if not already on, and then begins the PS-3 inducer
learning routine.
•
The furnace IFC will send a digital signal to the variable
speed inducer drive to run the inducer motor at the
preset factory 100% (high) heat RPM.
•
The furnace IFC waits for PS-3 pressure switch to close.
A 24 Volt AC signal is sent to the furnace IFC when the
pressure switch closes.
•
If PS-3 does not close at the factory preset 100% (high)
heat RPM, the furnace IFC will continue to signal the
variable speed inducer drive to increase the inducer
speed in steps until PS-3 closes or until the maximum
RPM for 100% (high) heat is reached.
•
The furnace IFC enters a time delay so that the heat
exchanger and the recuperative cell warm up to their
high heat operating temperature. At the end of this time
delay, the inducer discharge air temperature will be at
its high heat operating temperature and the density of
the products of combustion will be stabilized.
•
The furnace will now signal the variable speed inducer
drive to reduce the inducer speed in steps until PS-3
opens.
•
When PS-3 opens, the furnace IFC will NOTE the inducer
motor RPM.
•
The furnace IFC then adds an additional number of RPM
to the 100% (high) heat inducer motor NOTED RPM
until PS-3 closes.
•
The furnace IFC now stores this learned inducer
operating RPM for 100% (high) heat in its memory.
•
The furnace IFC will use this stored learned inducer
operating RPM for 100% (high) heat calls it receives
in the future.
•
If PS-3 is not closed when the inducer reaches its
maximum RPM, the furnace IFC will signal the variable
speed inducer drive to reduce the inducer Motor speed
in steps to its low heat LEARNED SPEED.
•
The furnace IFC flashes its Red Fault LED three times
repeatedly. The furnace IFC will keep operating at low
heat for 10 minutes and then retry the PS-3 learning
routine.
