Key Control Logics; Cooling Control; Heating Control - Gree LSQWRF35VM/NhA-M Service Manual

2.3 Key control logics

2.3.1 Cooling control

Freeze protection
◆
For each single unit, when the leaving water temperature is lower than the anti-freezing setpoint,
freeze protection will work; when the leaving water temperature go higher than the normal value, freeze
protection will be removed.
When the anti-freezing temperature and the leaving water temperature are between the anti-freezing
setpoint and the normal value, the unit will keep the current operation status.
Shutdown
◆
Manual and timer shutdown: compressors, fans and then water pumps will stop.
Shutdown at the set temperature: compressors and fans will stop but water pumps will still be working.
Shutdown due to malfunction: compressors and fans will stop but water pumps will still be working.

2.3.2 Heating control

Over-temperature protection for heating
◆
For each single unit, when the leaving water temperature goes higher than the anti-over-temperature
setpoint, over-temperature protection will work and the operation frequency of the compressor (or
dual compressors) will be lowered until the leaving water temperature is lower than the setpoint. Stop
compressors one by one if the operation frequency has been recorded the lowest and the leaving
temperature remains above the setpoint for 1 minute.
With the leaving water temperature back to normal, over-temperature protection will be removed. If
it occurs with a reduced frequency, the compressor should be controlled by the water temperatures for
working as normal.
Control to the auxiliary electric heater
◆
When the control function of the auxiliary electric heater has been activated through the control panel,
the unit is able control the auxiliary electric heater.
The auxiliary electric heater is able to work automatically as long as there is no fault of the flow switch
and all entering and leaving water temperature sensors work normally.
When the control function of the auxiliary electric heater has been activated through the control panel,
the auxiliary electric heater will not work any more.
When all entering and leaving water temperature sensors are faulty, the auxiliary electric heater will
stop working.
When any flow switch fails, the auxiliary electric heater will stop working.
When over-temperature protection for heating works but the auxiliary electric heater is still required for
operation, it will work continuously when its heating task is finished.
Shutdown
◆
Manual or timing shutdown: compressor stops firstly, and the auxiliary electric heater secondly, and
then the fan and the water pump stop.
Shutdown upon the temperature set point: the compressor and the fan stop firstly, while the water
pump keeps running.
Shutdown upon errors: the compressor stops firstly and the fan stops, while the water pump keeps
running.
Unit Control
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