Continuous Blower-The comfort level of the living
space can be enhanced when using this feature by
allowing continuous circulation of air between calls for
cooling or heating. The continuous circulation of air occurs
at half the full cooling airflow rate. To use this feature,
place the thermostat fan switch into the ON position.
Cooling Airflow Ramp Up - At the beginning of a call for
cooling, the blower will run at 80% of full airflow for 7.5
minutes. This improves the system's moisture removal and
saves blower power during cooling start.
Reduced Airflow Operation (Dehumidification) - For
situations where humidity control is an issue, the variable
speed motor can be connected to operate at a 25%
reduction in the normal airflow rate. The variable speed
motor interface board provides for connection of a humi-
distat on the HUM terminal. When a humidistat is con-
nected, the dehumidifier resistor on the interface must be
cut. The humidistat should be wired to open during high
humidity, which will reduce blower airflow.
Safety Controls
The control circuit includes the following safety controls:
Limit Control
This control is located inside the heating compartment and is
designed to open at abnormally high air temperatures. It
resets automatically. The limit control operates when a high
temperature condition, caused by inadequate airflow, occurs.
This causes the ignition control to close the gas valve. The
circulation air blower continues to operate in this situation.
Pressure Switch
The pressure switch prevents the gas valve and igniter
from being energized if there is insufficient combustion air
due to a failed combustion blower or a blocked vent.
Flame Sensor
Ifthe ignitioncontrol does not receive a signal from the flame
sensor indicating that the burners have established flame, the
gas valve closes after the 10-second trial for ignition period.
Rollout Switch
The switch is located above the main burners. In the event
of a sustained flame rollout, the rollout switch causes the
ignition control to close the gas valve. To reset, push the
button on top of the switch.
Auxiliary Limit (42, 48, and 60 units only)
This control is located in the side of the circulation air
blower housing. The switch causes the ignition control to
close the gas valve should the circulation blower fail to
operate. This control resets automatically.
MAINTENANCE
It is recommended that this furnace be inspected by a
qualified service technician at the beginning of each
heating season.
Filters
Filters should be checked at least every 6 weeks. Dispos-
able filters should be replaced when dirty, and cleanable
filters should be cleaned regularly. It is important to keep the
air filters clean, as dirty filters can restrict airflow and the
blower and induced draft motors depend upon sufficient air
flowing across and through them to keep from overheating.
Lubrication
The blower motor and induced draft motor are pre-lubricated
by the manufacturer and do not require further lubricating
attention. However, the motors should be cleaned periodi-
cally to prevent the possibility of overheating due to an
accumulation of dust and dirt on the windings or on the
motor exterior.
Burners
Light the burners and allow to operate for a few minutes to
establish normal burning conditions. Observe the burner
flames. Compare this observation to Figure 10 on page 14
to determine if proper flame adjustment is present. Flame
should be predominantly blue in color and strong in appear-
ance. Check that all burners are lit, and that the flame does
not impinge on the sides of the heat exchanger.
Distorted flame or yellow tipping of the natural gas burner
flame, or long yellow tips on propane, may be caused by
# 48111B005 Page 13
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