MS-SVN052E-EN 19
System Operation
System Operation
Control Logic Description
The variable speed system adopts the same 24VAC control as conventional heat pumps.
Compressor speed is controlled according to coil pressures monitored by the pressure transducer.
In order to ensure stable and appropriate capacity, compressor speed is modulated in accordance
with evaporator pressure during the cooling mode, and in accordance with condensing pressure
during the heating mode. Nominal pressure can be adjusted automatically at the SW4 switch to
reach optimized compressor operational capacity, as well as to satisfy higher dehumidifying and
capacity demands.
SW4
Sensor
T3 (Outdoor coil temperature) and T4 (indoor temperature
heat pump only).
T5 (Compressor discharge temperature and Tf (IPM radiator temperature)
Pressure Transducer.
Sensor Description
T3 temperature sensor is used for:
– Protection during system operation (high/low coil temperature)
– Outdoor fan control (cooling)
– Defrost (heat pump only)
– Forecasting environment temperature (cooling only)
T4 sensor is required (heat pump only) for:
– Enabling system operation according to outdoor temperature
– Indicating one of the conditions for enabling defrost cycle
– Outdoor fan control (heating mode heat pump only)
T5 sensor is required for:
– Operational protection (high/low temperature)
– Control of outdoor electronic expansion valve (heat pump only)
ON
OFF 1234
SW4-1 Not Used
SW4-2 Not Used
SW4-3
ON
Adaptive capacity output
disable
OFF
Adaptive capacity output
enable
SW4-4
ON Accelerated cooling/heating
OFF Normal cooling/heating
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