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Two-Stage Models:
There is an adjustable HEAT FAN OFF delay of approximately
90/120/150/180 seconds (factory set at 150). If the unit is
operating at high stage when the call for heat is removed, the
blower will operate for 30 seconds at high heat speed then
switch to low heat speed for the remainder of the selected
HEAT FAN OFF delay.
Cooling
1. Thermostat calls for cooling. The compressor and outdoor
fan are energized.
Two-Stage Models:
If the thermostat call is for low stage cooling, the compressor
and outdoor fan are energized at low stage. If the thermostat
call is for high stage cooling, the compressor and outdoor
fan are energized at high stage.
2. Approximately seven seconds later, the indoor fan starts.
3. The unit will deliver cooling to the conditioned space until
the thermostat is satisfied.
4. The compressor and outdoor fan will be de-energized when
the thermostat opens.
5. The indoor fan continues to run for approximately 60
seconds after the thermostat is satisfied.
Two-Stage Models:
The fan runs at low cool speed for the off delay period.
This allows additional cooling from the indoor coil to be
transferred to the conditioned space. Then, the indoor fan
stops.
NOTE: A 180-second anti-short cycle is integral to the control and
prevents recycling of the compressor.
Fan Only
1. Thermostat calls for FAN ONLY by energizing "G".
2. Approximately seven seconds later, the indoor fan starts.
Two-Stage Models:
Indoor fan is energized at low heat speed.
3. The indoor fan continues to run for approximately 60
seconds after "G" is de-energized.
Two-Stage Models:
The indoor fan is immediately de-energized once the
thermostat "G" is de-energized.
STARTUP, ADJUSTMENTS, AND CHECKS
Heating Startup
This unit is equipped with an electronic ignition device to
automatically light the main burners. It also has a power vent
blower to exhaust combustion products.
On new installations, or if a major component has been
replaced, the operation of the unit must be checked.
Check unit operation as outlined in the following instructions. If
any sparking, odors, or unusual sounds are encountered, shut
off electrical power and recheck for wiring errors, or obstructions
in or near the blower motors. Duct covers must be removed
before operating unit.
Rollout Protection Control
The rollout protection device opens, cutting power to the gas
valve, if the flames from the burners are not properly drawn into
the heat exchanger. The rollout protection device is located on
the burner bracket. The reason for elevated temperatures at
the control should be determined and repaired prior to resetting
this manual reset control.
O AVOID PROPERTY D AMAGE, P ERSONAL INJURY OR DEATH DUE T O FIRE
T
OR E XPLOSION, A QUALIFIED SERVICER M UST INVESTIGATE THE REASON F OR
THE ROLLOUT P ROTECTION DEVICE T O OPEN B EFORE MANUALLY R ESETTING
THE ROLLOUT P ROTECTION DEVICE.
Rollout Protection on Burner Bracket
Secondary Limit Control
The secondary limit control is located on the top of the blower
scroll assembly. This control opens when elevated temperatures
are sensed. Elevated temperatures at the control are normally
caused by blower failure. The reason for the opening should
be determined and repaired prior to resetting.
If the power to the unit is interrupted during the heating
cycle, it may cause the secondary limit to trip. Once the
blower compartment temperature drops below the limit reset
temperature, the limit will automatically reset.
Back of Unit
Secondary Limit Control
Pre-Operation Checks
1. Close the manual gas valve external to the unit.
2. Turn off the electrical power supply to the unit.
13
WARNING
Rollout Protection
Secondary
Control Limit
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