Unit Control
resumes operation when defrosting ends up.
2.7 Control to the 4-way Valve
The 4-way valve always keeps on under the cooling mode and will off after the compressor starts up
under the heating or water heating mode. When the unit comes into defrosting, the 4-way valve will be
on and resume the off status when defrosting ends up. For shutdown under the heating mode, the 4-way
valve will be closed after the compressor stops.
2.8 Control to the Water Pump
The water pump firstly will run at the initialized speed and then adjust the speed according to the
entering/leaving water temperature difference. When the temperature difference is large, the fan runs at
the high speed. When the temperature difference is small, the fan runs at the low speed.
2.9 Control the Electrostatic Expansion Valve
There are two electrostatic expansion valves for two-stage throttling control. The opening angle of the
first-stage electrostatic expansion valve is adjusted based on the ratio of readings of the high-pressure
sensor, low-pressure sensor and enthalpy-adding sensor. The opening angle of the second-stage is
adjusted based on the suction superheating degree.
2.10 Protection Control
(1) Compressor Low-pressure Protection
When it is detected continuously that pressure at the low side is too low, then low-pressure protection
will occur and this error will be displayed at the controller, all loads act as per the shutdown sequence.
This error is unrecoverable and can be cleared unless repowered on.
(2) High Discharge Temperature Protection
When it is detected continuously that the discharge temperature is higher than the recoverable
temperature, the electrostatic expansion valve will turn to the maximum opening angle with large step
until the discharge temperature is lower than the recoverable temperature. However, if this condition
remains, the compressor will restrict the frequency output or lower its frequency three times. At any time,
if it is detected that the discharge temperature is higher than the set point for protection for three
seconds, the compressor will stop and the unit comes into high discharge temperature protection.
(3) Compressor Hi-pressure Protection
In any case, when it is detected that the high-pressure switch acts, the unit will come into
high-pressure protection three seconds later. This protection is unrecoverable.
(4) Flow Switch Protection
In any case, when it is detected that the flow switch of the main unit disconnects, then all loads except
the water pump of the solar system and the auxiliary electric heater of the water tank will stop. This
protection is unrecoverable. The unit is allowed to be restart only after this error is cleared and the unit is
repowered on.
(5) Communication Error
When the indoor unit main board or drive board does not receive correctly any data from the unit main
board, all loads will stop.
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