GF - A 6
Furnace Sequences Of Operation
IFC Inducer Learning Routine Sequence
· The furnace IFC will go through an inducer learning
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 maintained
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 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.
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
· 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.
· 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.
NOTE:
The furnace lights at approximately 65% of capacity.
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IFC Inducer Learning Routine Sequence
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