Unit Control
water heating range of the main unit, the water tank heater will start. At any time, only one between the
auxiliary electric heater and the water tank heater is allowed to run.
Over-temperature Protection for Water Heating
When the compressor is running, if it is detected that the leaving water temperature of the auxiliary
electric heater of the main unit is higher than the over-temperature protection temperature, the
compressor will lower its operating frequency until it reaches the minimal operating frequency. At this
point, if it is still detected that leaving water temperature is still lower than the over-temperature
protection, all loads except the water pump of the main unit and the 4-way valve will stop.
Over-temperature protection will exit when the leaving water temperature is lower than the
over-temperature protection temperature. Then, the main unit will resume normal operation.
2.3.2 Water Heating by the Solar System
When the solar water heating system is equipped but temperature difference ( it is the difference of
solar panel temperature and the actual water tank temperature) for startup is not satisfied, the water
pump of the solar system will not start. When the temperature difference is satisfied, the water pump will
start. However, when it is detected that the water tank temperature reaches the set point, or the
entering/leaving water temperature difference of the solar panel is too small, then this water pump will
stop running.
2.4 Shutdown
There are three kinds of shutdown conditions: normal shutdown, shutdown with some error, shutdown
for protection
Shutdown sequence: for normal shutdown, the compressor lowers its frequency firstly to the minmum
value, while for shutdown with some error or for protection, the compressor will stop directly.Then, the
electrostatic expansion valve turns to the maximum opening angle; the fan stops after the compressor
has stopped; the water pump of the main unit stops after the compressor has stopped; the electrostatic
expansion valve turns the maximum opening angle to the fixed opening angle.
During shutdown under the heating and water heating modes, the 4-way valve will be powered off
after the compressor has stopped.
For shutdown owing to some error (except the communication error) or protection, the 4-way valve will
keep the power-on status.
For shutdown owing to communication between the unit and the wired controller, the 4-way valve will
be powered off some timer later.
For shutdown with some error or for protection, the electrostatic expansion valve will keep the
maximum opening angle.
2.5 Control to the Compressor
When the unit is controlled by the leaving water temperature, the output frequency of the compressor
is adjusted by the difference between the actual water temperature and the leaving water temperature
set point. When the unit is controlled by the room temperature, the output frequency of the compressor is
adjusted by the difference between the actual room temperature and the room temperature set point.
2.6 Control to the Fan
Under the cooling mode, the operating frequency of the fan is adjusted according to pressure at the
high pressure side. Under the heating or water heating mode, the operating frequency of the fan is
adjusted according to the pressure at the low pressure side. During defrosting, the fan stops and
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