AIR SOURCE HEAT PUMP WATER HEATER SERVICE MANUAL
10
temperature sensor. If the outdoor ambient temperature is not lower than -7
detected and start up conditions of the compressor are met, the system starts by following the hot water
sequence.
2) Control on fan motor
When start up conditions of the compressor are met, the system starts by following the hot water
sequence. The electronic expansion valve resets and is initialized, and the external fan motor starts.
After 10s, the compressor starts. The fan motor will determine whether to still run at high level or to run at
low level based on the ambient temperature after it runs at high level. If the system enters overload
control, the fan motor will switch to discontinuous start up and shutdown status at low level.
3) Control on defrosting
When the compressor is initially powered on and started, it determines the defrosting condition after
running for the preset duration. If the defrosting condition is met, the system defrosts before running in
hot water mode (including freeze-proofing operation of compressor). After defrosting is over, the
compressor starts for heat up. When the cumulative operation time exceeds or equals to the preset time
for defrosting, defrosting will be performed if the relation between the outdoor exchanger pipe
temperature sensor Th and the outdoor ambient temperature sensor Te meets the defrosting condition.
4) Control on water return pump
The water return pumps runs in automatic or manual control mode as set by users. In automatic
control mode, the water return pump is control based on temperature of the return pipe thermo-bulb. In
manual control mode, the return pump is stopped after water return is complete.
Notes: GRS-2.4/D270ANbA-K unit have not the function.
5) Control on freeze-proofing function
In the Off state, if water temperature in the water tank detected by the system based on the ambient
temperature is too low, the unit starts the freeze-proofing function immediately.
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