Key Control Logics; Cooling Control; Heating Control - Gree A Series Service Manual

4.3

Key Control Logics

4.3.1

Cooling Control

4.3.1.1 Freeze-up Protection
For each single unit, when the anti-freezing temperature or the leaving water temperature is
lower than the limit value, freeze protection will work; when the anti-freezing temperature and
the leaving water temperature go higher than the normal value, freeze protection will quit.
when the anti-freezing temperature and the leaving water temperature are between the limit
value and the normal value, the unit will keep the current operation status.
4.3.1.2 Shutdown
Manual and timely 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.
4.3.2

Heating Control

4.3.2.1 Over-temperature Protection for Heating
For each single unit, when either anti-over-temperature value or the leaving water
temperature goes higher than the targeted value, over—temperature protection will work and
the operation frequency of the compressors will be lowered until the anti-over-temperature
value or the leaving water temperature is lower than the targeted level. Stop compressors one
by one, if the operation frequency has been recorded the lowest and either the anti-over-
temperature value or the leaving temperature remains above the targeted level for 1 minute.
With the anti-over-temperature value or the leaving water temperature below the normal
level, overheating protection will quit. If it occurs with a reduced frequency, the compressor
should be controlled by the water temperatures for working as normal.
4.3.2.2 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.
A Series Modular-type Air-cooled (Heat Pump) Chiller
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