A5HL5-SF-1A-EN
13
Sequence of Operation
Control Operational Overview
The systems operation mode will be determined by the
24V control signal from the thermostat. This controls
the output actions of the indoor fan motor, electric
auxiliary heat, compressor, outdoor fan motor,
switchover valve and electronic expansion valve to
achieve cooling and heating functions.
There is a digital display on the outdoor unit control
board for indicating the operating status. The first digit
and second digit of DSP1 display normally blank, and if
there is protection or fault, it will be displayed. The
specific fault codes are described in the technical
service manual; The third digit of DSP1 displays the
operating status of the outdoor unit.
The third bit of DSP1 display The operating system of the outdoor unit
0
Off state. The startup signal is not received.
1 Power signal received. Ready to start.
2 Cooling mode operation
3 Heating mode operation
4 Oil return operation
5
Defrosting operation
6 Forced defrosting operation
7 Forced cooling operation
8 Forced heating operation
9 Testing mode operation
A
Fault or protection shutdown state
C
Refrigerant charging mode
H Dehumidification mode operation
q Seattle low noise mode operation
Cooling Mode (Heat Pump)
When the thermostat calls for cooling, the circuit from
R to G is completed. The blower motor is energized by
the fan control, which receives the 24VAC signal from
the control.
The circuit from R to Y is also complete, energizing the
inputs at the outdoor unit for cooling operation.
The compressor will start after the outdoor fan motor
runs for 2 seconds. The rotational speed of the outdoor
fan motor is automatically adjusted based on the
compressor frequency, outdoor ambient temperature,
and coil temperature. In general, the outdoor fan motor
runs at a higher speed when the outdoor ambient
temperature and the compressor rotation speed are
high, and the outdoor fan motor runs at a lower speed
when the outdoor ambient temperature and the
compressor rotation speed are low.
Heat Pump Heating Mode of
Operation
When the thermostat calls for heating, the circuit from
R to G is completed. The blower motor is energized by
the fan control, which receives the 24VAC signal from
the control. The circuit from R to Y and R to O are also
completed energizing the inputs at the outdoor unit for
heat pump operation.
The compressor will start after the outdoor fan motor
runs for 2 seconds, and the switchover valve will get
power immediately when the compressor runs. The
rotational speed of the outdoor fan motor is
automatically adjusted based on the compressor
frequency, outdoor ambient temperature, and coil
temperature.
In general, the outdoor fan motor runs at a lower speed
when the outdoor ambient temperature and the
compressor speed are high, and the outdoor fan motor
runs at a higher speed when the outdoor ambient
temperature and the compressor speed are low.
The electronic expansion valve is at the maximum
opening when on standby, and the valve opening will
be adjusted according to the system parameters to
ensure the rationality of the control system under
various environmental conditions, such as exhaust
temperature and exhaust pressure. In general, when
the exhaust temperature is lower than the set value, the
opening of the electronic expansion valve will
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