Air-to-water Heat Pump Split Versati
27
SPLIT TYPE
2.9 Control the Electronic Expansion Valve
There are two electronic expansion valves for two-stage throttling control. The opening angle of the first-stage
electronic 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
electronic 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) Refrigerant Loss Protection
When the unit receives the “On” demand (through On/Off key operation or automatic freeze protection), it
will immediately detect the temperature of the high-pressure sensor and the environment temperature. If the
temperature of the high-pressure sensor is lower than the set point, this error will be displayed with the error
indicating LED flashing. In this case, the unit is not allowed to start up unless this error does not exit. Once the
compressor starts up, the system will no longer detect refrigerant loss protection.
(4) Water Pump Protection
When it is detected continuously for three seconds that the unit comes into water pump overload protection,
then all loads except the water pump of the solar system and the auxiliary electric heater of the water tank will
stop. Three minutes later, all loads resume normal operation. When it is detected three times within 60 minutes that
the unit comes into water pump overload protection, this error will be displayed and is unrecoverable. The unit is
allowed to restart only after the unit is shut down manually and this error is cleared.
(5) 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.
(6) 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.
(7) 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 and vice versa.
