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The outdoor unit main board also controls the position of the
EEV (Electronic Expansion Valve)
to regulate the flow of refrigerant to the indoor unit evaporator
coil.
Temperature Sensors
Four temperature sensors located in the outdoor unit provide
temperature information to the outdoor unit main board for
control of the system during cool mode.
The outdoor ambient temperature sensor provides the
temperature of the air drawn into the condenser coil of the
outdoor unit.
The defrost temperature sensor provides the temperature
sensed at the output of the condenser coil.
The suction line temperature sensor provides the temperature
sensed at the incoming suction line pipe.
The compressor discharge sensor provides the temperature
sensed at the discharge pipe of the compressor.
Call to Terminate Cooling
The system will call to terminate cooling when the indoor
ambienttemperature sensor is equal to or lower than 2°F from
the room set temperature. The indoor control board will
communicate to the outdoor control board to de-energize the
compressor. The outdoor fan will run for 60 seconds before
stopping.
The indoor fan motor and louver will continue operating after
cooling has been terminated.
To stop cool mode, press the power button to turn the system
off, or change to another mode.
Freeze protection function
To prevent freezing of the indoor unit coil during cool mode,
when the compressor operates continuously for 10 seconds
and the temperature of the indoor coil has been below 32°F
for 10 seconds, the compressor will stop, and the error will
be shown. The indoor unit fan will continue to operate.
When the temperature of the indoor coil rises to 45°F for
more than 3 minutes the compressor will restart and the
system will continue functioning.
Heat Mode
Overview
The temperature control range in heating mode is 60°F - 86°F.
The temperature set by the remote control and the indoor
unit ambient temperature sensor will determine if a call for
heat is needed. If a call for heat is justified, a temperature
compensation adjustment is automatically added to the
operating parameter and the call is communicated from the
indoor unit to the outdoor unit.
The indoor unit louver will open using a stepper motor. The
indoor fan will not operate at this time.
The outdoor unit will shift the 4-way valve to the heat mode
position and determine the position of the EEV and speed
(frequency) of the compressor. There can be adelay of up to
3 minutes before the outdoor unit fan and compressor start.
(Tr = room temperature Ts = set temperature)
If TU ” Ts, the outdoor unit will operate and the indoor fan
operates in cold air prevention function
If Tr > Ts+, the outdoor unit turns off and the indoor fan
operates at heat residue sending mode.
If Tr < Ts+, the outdoor unit will restart and the indoor fan
operates in cold air proof mode.
The speed of the indoor fan can be controlled manually by
the user or automatically by the system. The speed can be
changed between HIGH, MEDIUM, and LOW. The
predetermined conditions for automatic control are as
follows:
High Speed: Tr < Ts
Medium Speed: TV ” TU ” Ts + 4°F
Low Speed: Tr > Ts + 4°F
When the indoor fan is running in automatic mode there
is no delay when the speed switches from high to low. There
is a 3 minute delay when manually switching speeds from
HIGH to LOW.
Cold Air Proof Operation
At initial start of heat mode, indoor blower will not be turned
on until indoor coil temperature senses a minimum
temperature. This period usually takes 30 seconds to 3
minutes depending on the outdoor ambient temperature.
4 minutes after the indoor fan starts, the LOW speed will
change to the set speed.
Residual heat sending: the indoor fan will sitll operate on low
speed for 12 seconds when the conditioner is turned off.
The outdoor unit temperature sensors: outdoor ambient,
defrost, suction line, and compressor discharge, used in
conjunction with the indoor temperature sensors, indoor
SEQUENCE of OPERATION
PAGE 27
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