GF - A 23
Furnace Sequences Of Operation
*UH3 Inducer Learning Routine Sequence
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2
3
4a
4e4c 4d4b
5a 5b
7
9
10
8
5c
6a 6b
The furnace will start the heating cycle in second stage, if not
already on, and then begins the third stage learning routine.
The furnace checks pressure switch three, PS-3, it must be open.
When the furnace IFC detects that PS-3 is open, it will
send a digital signal to the variable speed inducer drive to
run the inducer motor at the preset factory third stage RPM.
The furnaces looks for the PS-3 pressure switch to close.
The furnace IFC will continue to signal the variable speed
inducer drive to increase the inducer motor speed in
steps if PS-3 does not close when the preset factory third
stage RPM is reached. The maximum RPM for the third stage
heat is set at 5200 RPM.
When the furnace IFC detects PS-3 is closed, it signals the
variable speed indoor blower to operate at its third stage heating
airflow.
The furnace IFC enters a time delay so that the heat exchanger
and the recuperative cell warm up to their third stage operating
temperature. At the end of this time delay, the inducer discharge
air temperature will be at its third stage operating temperature and
the density of the products of combustion will stabilize.
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 signals the motor drive
to increase the inducer speed by an additional number of
RPM. This is the learned operating RPM.
The furnace IFC will now store this learned operating inducer
RPM in its memory and use it for third stage heat calls it receives
in the future.
If PS-3 is not closed when the inducer reaches 5200 RPM the
furnace IFC will signal the variable speed inducer drive to
reduce the inducer Motor speed in steps to its second stage
LEARNED SPEED. The furnace IFC flashes its Red LED three
times repeatedly and also sends an Alert message to the comfort
control. The furnace IFC will keep operating at second stage of
heat until the comfort control sends a different signal.
Indoor blower timing
Heating: The Integrated Furnace Control module controls the
Indoor Blower. The Blower start is fixed at 45 seconds after
ignition. The FAN-OFF period is field selectable via the User
Interface menu at 60, 100, 140, or 180 seconds. The factory
setting is 100 seconds.
Cooling: Continuous Fan mode is 50% of the cooling CFM. This
is a selectable range on the Comfort Control menu.
5c
3 5c
6a
6b
5c
6a
6b
5c
5c
10
3
6b
6a
6b 5c
5c
3
6a
6b
5c
3
11
6a
6b
11
2
3
10
1
2
2
3
3
3
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