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rises outside the specified range could result in premature
heat exchanger failure.
Place thermometers in the return and supply air stream as
close to the furnace as possible. The thermometer on the
supply air side must be shielded from direct radiation from
the heat exchanger to avoid false readings. Adjust all
registers and duct dampers to the desired position and
run the furnace for ten to fifteen minutes before taking any
temperature readings. The temperature rise is the difference
between the supply and return air temperatures.
TWO STAGE CONDENSING UNIT
THERMOSTAT
Y1
CONDENSING
UNIT
Y1
Y2
YELLOW
Y1
Figure 23. Connections for Two Stage Cooling
Yellow (short) Y1
REMOVE BLUE
Y2
WIRE FROM
Y TERMINAL
OF
FURNACE
BOARD
BLUE
Y2
Blue Y2
Red R
Grey C
Green G
Figure 24. Connections to Furnace Circuit Board
WARNING:
!
To avoid electric shock, personal injury, or
death, disconnect the electric power before
performing any maintenance.
Verifying Burner Operation
To verify operation of the burners, make sure that the
furnace door is in place and that there is power to the
furnace. Set the thermostat to a temperature above room
temperature and observe the ignition sequence. The burner
flame should carry over immediately between all burners.
The flames should be blue, without yellow tips. Flames
should extend from each burner without lifting off, curling,
or floating. After verifying satisfactory flame characteristics,
set the thermostat to a temperature below room temperature
and verify that the burner flame extinguishes completely
Verify Operation of the Supply Air Limit Switch
To verify operation of the supply air limit switch, make
sure that the blower door is in place and that there is
power to the furnace. Block the return airflow to the
furnace by installing a close-off plate in place of or
upstream of the filter(s). Set the thermostat to a
temperature above room temperature and verify that the
Sequence of Operation is as described in these
instructions. The limit switch should function to turn off
the gas valve within approximately four minutes (the
exact time depending on the efficiency of the close-off
in blocking the return air to the furnace). The combustion
blower should continue to run when the limit switch
opens. Remove the close-off immediately after the limit
switch opens. If the furnace operates for more than four
minutes with no return air, set the thermostat to a
Yellow (long)
GAS VALVE
Black L1
White NEUTRAL
To Motor Plugs
27
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