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CONTROL
4.6 Normal operation
4.6.1 Component control in heating and domestic hot water mode
Component
Refer to wiring
diagram
Control functions and states
DC inverter compressor COMP
Controlled according to load requirement from
hydronic system
Fan FAN
Controlled according to outdoor heat exchanger
temperature
Electronic expansion valve EXV
Position (steps) from 0 (fully closed) to 480 (fully open),
controlled according to outdoor ambient temperature,
discharge temperature, suction overheating,
compressor speed and refrigerant circuit pressure.
4-way valve STF*/STF1** On
* Single-phase version
** Three-phase version
4.6.2 Component control in cooling mode
Component
Refer to wiring
diagram
Control functions and states
DC inverter compressor COMP
Controlled according to load requirement from
hydronic system
Fan FAN
Controlled according to outdoor heat exchanger
temperature
Electronic expansion valve EXV
Position (steps) from 0 (fully closed) to 480 (fully open),
controlled according to outdoor ambient temperature,
discharge temperature, suction overheating,
compressor speed and refrigerant circuit pressure.
4-way valve STF*/STF1** O
* Single-phase version
** Three-phase version
4.6.3 Compressor control
The compressor rotation speed is controlled according to the load requirement.
Before compressor startup, the outdoor unit determines the speed according to outdoor ambient temperature, the set-
point and actual water outlet temperature, as shown in paragraph 4.3.2.
Once the startup program is complete, the compressor runs at the set rotation speed.
During operation, the compressor speed is controlled according to the variation ratio of the water temperature, the
water pressure and the refrigerant temperature.
4.6.4 Compressor control step
The operation speed of six-pole compressors in rotations per second (rps) is one third of the frequency (in Hz) of the
electrical input to the compressor motor.
The frequency of the electrical input to the compressor motors can be altered at a speed of 1Hz per second.
4.6.5 4-way valve control
The four-way valve is used to change the direction of refrigerant flow through the water side heat exchanger in order
to switch between cooling and heating/DHW modes. Refer to paragraphs 3.2 and 3.3.
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