air limitswitchopens.Removethe close-off
plateimmediatelyafterthesupplyairlimitswitch
opens.Ifthefurnaceoperatesformorethanfive
minuteswithnoreturnair,setthe thermostat
belowroomtemperature,shutoffthepowerto
the furnace,andreplacethe supplyair limit
switch.
DESCRIPTION OF COMPONENTS
Figure 29 shows the location of each of the
functional components described below. If any
component of the furnace must be replaced,
use only factory authorized replacement parts.
Contact your distributor for the approved re-
placement parts.
Flame Sensor - The flame sensor acts to
prove that flame has carried over from the
ignitor to the opposite end burner. If no flame is
sensed, the furnace will be shut down automati-
cally.
Gas Valve = The gas valve controls the flow of
gas to the burners. When the gas valve is
energized it automatically opens and regulates
the gas pressure in the manifold.
Pressure Switch = The pressure switch veri-
fies that the inducer is drawing the combustion
gases through the heat exchanger. Italso senses
a blocked condensate drain condition.
Deck Limit Switch (Auxiliary Limit) - The
deck limit protects the furnace filter tempera-
ture from overheating when the motor has
malfunctioned. If the deck switch opens, the
power for the furnace will shut down (see Figure
29).
Supply Air Limit Switch = The supply air limit
switch prevents the air temperature leaving the
furnace from exceeding the maximum outlet air
temperature.
Vent Safety Switch - The vent safety switch
shuts the furnace down if the outlet flue gas
temperature increases above 145°F. This
switch protects the plastic flue system and the
inducer from over-temperature conditions.
Flame Roll-Out Switch - This switch pro-
vides flame roll=out protection to the furnace
and combustion air inlet pipe.
MAINTENANCE
It is recommended that the furnace be checked
yearly. At a minimum, this check should include
the following items:
z: WARNING:
To avoid electricshock, personal injury,
or death, turn off the power at the
disconnect or the main service panel
before performing any maintenance.
z WARNING:
Holes in the vent pipe or heat exchanger
can cause products of combustion to
enter the occupied space. Replace the
vent pipe or heat exchanger if leaks are
found. Failure to prevent products of
combustion from being circulated into
the occupied space can crate poten-
tially hazardous conditions, including
carbon monoxide poisoning, that could
result in personal injury or death.
Combustion Air and Vent System
Check the combustion air and vent pipe to
ensure that it is not damaged, corroded or
blocked by debris. Any damaged section of
vent pipe must be replaced, and any obstruc-
tion or blockage must be removed prior to
operating the furnace.
Air Filter
An air filter is supplied with the furnace as
shipped from the factory. Filters should be
changed or cleaned monthly during the heating
season. New or newly renovated homes may
require more frequent changing until the con-
struction dust has been removed.
/ WARNING'.
Never operate the furnace without a
filter in place, Dust and lint in the return
air can build up on internal compo-
nents, resulting in loss of efficiency,
equipment damage, and possible fire,
29
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