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FIGURE 28
DOWNFLOW BLOWER REMOVAL
SAFETY FEATURES
LIMIT CONTROL
The high limit cut-off is set at the
factory and cannot be adjusted. It is
calibrated to prevent the air
temperature leaving the furnace from
exceeding the maximum outlet air
temperature. If temperature exceeds
the maximum outlet air temperature,
the limit will shut the furnace down.
Reasons which could cause the outlet
temperature to exceed the range are
failed indoor blower, dirty filters, etc.
OVER TEMPERATURE
SAFETY SWITCHES
Furnaces are equipped with safety
switches to protect against
overtemperature conditions in the
control compartment caused by
inadequate combustion air supply. In
the event of an overtemperature
condition, the switch will shut the
furnace down. The switch for the
dedicated UPFLOW FURNACE and
DOWNFLOW is located just above the
burners on the blower divider panel.
Switches for the UPFLOW/
HORIZONTAL AND HORIZONTAL
ONLY HOT SURFACE IGNITION
FURNACES are located on either side
of the burner brackets and just above
the burners on the blower divider
panel. If a switch is tripped, it must be
manually reset. DO NOT jumper this
switch. If this switch should trip, a
qualified installer, service agency or
the gas supplier should be called to
check and/or correct for adequate
combustion air supply. If this unit is
mounted in a closet, the door must be
closed when making this check.
A failed inducer motor would be a
cause of inadequate combustion air.
DO NOT reset the over temperature
switch without taking corrective action
to assure that an adequate supply of
combustion air is maintained under all
conditions of operation. Replace this
switch only with the identical
replacement part.
LUBRICATION
The blower motor and induced draft
motor are prelubricated by the
manufacturer and do not require
further attention.
The motor must be cleaned
periodically by a qualified installer,
service agency, or the gas supplier to
prevent the possibility of overheating
due to an accumulation of dust and dirt
on the windings or on the motor
exterior. And, as suggested elsewhere
in these instructions, the air filters
should be kept clean because dirty
filters can restrict airflow and the motor
depends upon sufficient air flowing
across and through it to keep from
overheating.
PRESSURE SWITCH
This furnace has a pressure switch for
sensing a blocked vent condition. It is
normally open and closes when the
induced draft blower starts, indicating
air flow through the combustion
chamber. As stated, a blocked vent
condition will cause the pressure
switch to remain open as will a failed
inducer, a crack in the pressure switch
hose, etc.
33
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