AAON RL-240 - Manual (Page 51)

51
Operation
Unit operations should be controlled with
thermostat, or unit controller, never at the
main power supply, except for emergency or
complete shutdown of the unit.
Indirect Gas Heater Operation
When heat (G and W1, W2, etc.) is called
for the combustion motor starts and the
ignition control is energized. The control
sends 24 VAC to the gas valve and high
voltage to the igniter. If a burner flame has
been detected within 10 seconds, the spark is
extinguished and the flame continues. If a
flame has not been detected after 10
seconds, the gas valve closes, the spark
ceases and the induced draft blower
continues to purge the heat exchanger. After
45 seconds of purge, the ignition system will
attempt to light the burners again. Should no
flame be detected after 3 tries, the ignition
control will lock out the system. Power to
the ignition control must be cycled to reset
the heater control.
On a fault the gas train is shut down by a
main limit located in the heat exchanger area
or by an auxiliary limit mounted in the
supply fan compartment.
Electric Heating Operation
When a call for heating (G and W1, W2,
etc.) is made the supply fan motors and
electric resistance heaters will energize.
Heating
is accomplished by passing
electrical current through a specified amount
of resistance heaters which will produce the
required heat.
On a fault condition the main limit located
in the supply air or the auxiliary limit
located downstream of the supply fan will
remove power from all contactors.
Steam or Hot Water Preheating and
Heating Operation
Valve control for steam and hot water
heating coils are by others. Heating is
accomplished by passing steam or hot water
through the steam or hot water coil
assembly.
Packaged DX Cooling Operation
When a call for cooling (G and Y1, Y2, etc.)
is made the supply fan motors and
compressors will energize.
Chilled Water or Non-Compressorized
DX Cooling Operation
Controls for chilled water cooling coils and
non-compressorized DX coil are by others.
COMPRESSOR CYCLING
5 MINUTE MINIMUM OFF TIME
To prevent motor overheating
compressors must cycle off for a
minimum of 5 minutes.
5 MINUTE MINIMUM ON TIME
To maintain the proper oil level
compressors must cycle on for a
minimum of 5 minutes.
The cycle rate must not exceed 6
starts per hour.
WARNING