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Common
Leads
Connect
Neutral
Lead of
Electronic
Air Cleaner
and/or Humidifier
Verifying Burner Operation
To verify operation of the burners, make sure
that the blower compartment door is in place and
that there is power to the furnace. Set the
thermostat above room temperature and ob-
serve the ignition sequence. The flame can be
observed through the small clear window on the
burner box. The burner flame should carry over
between all burners on high fire. Note that when
operating on low fire, the left two burners will not
operate on upflow models and the right two
burners on downflow models. The flames should
be blue, without yellow tips. Flames should
extend from each burner without lifting, curling,
or floating. After verifying ignition, set the ther-
mostat below room temperature and verify that
the burner flame extinguishes completely.
Verifying 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. Completely 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 above room tempera-
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Neutrals
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Here.
Humidifier Tap
(.5A@ 120 VAC)
Figure 29. Blower Speed Tap Location
3 Amp Fuse
Flame Signal
Light (Yellow)
Status
Light (Red)
Unused Motor
Leads
Electronic Air Tap
(.5A@ 120 VAC)
These motor speed taps are
not used for two-stage models
ture and verify that the Sequence of Operation is
as described in these instructions. The supply air
limit switch should function to turn off the gas
valve within approximately five minutes. The
circulating air and combustion blowers should
continue to run when the supply air limit switch
opens. Remove the close-off plate immediately
after the supply air limit switch opens. If the
furnace operates for more than five minutes with
no return air, set the thermostat below room
temperature, shut off the power to the furnace,
and replace the supply air limit switch.
DESCRIPTION OF COMPONENTS
Figure 30 shows the location of each of the
functional components described below. If
any component of the furnace must be re-
placed, use only factory authorized replace-
ment parts. See the Replacement Parts List
for each component.
Flame Sensor – The flame sensor acts to prove
that flame has carried over from the igniter to the
opposite end burner. If no flame is sensed, the
furnace will be shut down automatically.
37
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