Operating instructions

10
NORMAL SEQUENCES OF OPERATION
HEATING
This unit is equipped with an ignition control that automatically
lights the main burner. DO NOT attempt to light the main burners
by any other method.
1. Thermostat calls for heat. The induced draft blower energizes
for a 15-second pre-purge.
2. The spark igniter and gas valve energizes for seven seconds.
NOTE: The igniter produces a very intense electrical spark
that ignites the gas.
3. The 30-second HEAT FAN ON delay time begins.
4. The unit delivers heat to the conditioned space until the
thermostat is satisfied.
5. The gas valve deenergizes. The induced draft blower
continues operation for a 29-second post-purge.
6. Ignition control begins timing the HEAT FAN OFF delay. This
allows any additional heat in the heat exchanger to be
transferred to the conditioned space. After the HEAT FAN
OFF delay time has elapsed, the blower will deenergize.
Models with a PSC (Permanent Split Capacitor) circulator blower
motor have an adjustable HEAT FAN OFF delay of 90/120/ 150/
seconds OR 60/90/120/180 seconds. Models with variable
speed motor (ECM) have a fixed HEAT FAN OFF delay of 120
seconds.
COOLING
1. Thermostat calls for cooling. The compressor and outdoor
fan are energized.
2. Approximately seven seconds later, the indoor fan starts.
NOTE: Models with a variable speed motor (ECM) do not
have a seven-second COOL FAN ON delay. The motor
“ramps” up to full speed over a 30-second period.
3. The unit will deliver cooling to the conditioned space until
the thermostat is satisfied.
4. The compressor and outdoor fan will be deenergized when
the thermostat opens.
5. The indoor fan continues to run for approximately 30 seconds
after the thermostat is satisfied. This allows additional cooling
from the indoor coil to be transferred to the conditioned
space. Then, the indoor fan stops.
FAN ONLY
1. Thermostat calls for FAN ONLY by energizing “G”.
2. Approximately seven seconds later, the indoor fan starts.
NOTE: Not all models will have a “7-Second ON” indoor
fan start delay or an “OFF” delay in continuous fan mode.
3. The indoor fan continues to run for approximately 30 seconds
after “G” is deenergized.
STARTUP, ADJUSTMENTS, AND CHECKS
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.
HEATING STARTUP
Heat Anticipator Setting
Set the heat anticipator on the room thermostat to 0.4 amps to
obtain the proper number of heating cycles per hour and to
prevent the room temperature from overshooting the room
thermostat setting.
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 (see figure below). The reason for elevated
temperatures at the control should be determined and repaired
prior to resetting this manual reset control.
Rollout Protection
Rollout Protection Device
WARNING
T
O AVOID PROPERTY DAMAGE, PERSONAL INJURY OR DEATH DUE TO FIRE
OR EXPLOSION, A QUALIFIED SERVICER MUST INVESTIGATE THE REASON FOR
THE ROLLOUT PROTECTION DEVICE TO OPEN BEFORE MANUALLY RESETTING
THE ROLLOUT PROTECTION DEVICE.
Secondary Limit Control
A second limit control is placed on the blower scroll. This control
will open due to elevated temperature caused by the blower
failing. The reason for elevated temperatures at the control
should be determined and repaired prior to resetting. The
secondary limit control is located on the top of the blower scroll
assembly (see figure below).
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.
Blower
Compartment
Access Door
Blower
Assembly
Secondary
Limit Control
Condenser Coil
Duct
Openin
g
Top View
Secondary LImit Control