Standby Control; Startup Control; Crankcase Heater Control; Startup Sequence And Frequency Control In Combination Modules - Midea VRF Series Service Manual

V6R VRF 50/60Hz

3 Standby Control

3.1 Crankcase Heater Control

The crankcase heater is used to prevent refrigerant from mixing with compressor oil when the compressors are stopped. The
crankcase heater is controlled mainly according to discharge temperature.
When the discharge temperature is above 45°C, the crankcase heater is off; when the discharge temperature is below 40°C,
the crankcase heater turns on if one of the three conditions is matched:
1. The first time powered on
2. In defrost operation
3. Ambient temperature < 10 °C and the compressor stops for more than 4 hours

4 Startup Control

4.1 Startup Sequence and Frequency Control in Combination Modules

During the start-up process, the control of the compressor and the heat exchange mode is uniformly judged by the master
outdoor unit, and the electronic expansion valve and solenoid valve are self-judged by the salve unit according to its own
sensor status.
During the start-up process, the compressor frequency is based on the displacement frequency of the 70cc compressor.
After the main outdoor unit is weighted and evenly distributed to each slave unit according to the maximum frequency, each
slave unit performs the displacement frequency and convert it to actual frequency.
When combinational modules are started in parallel, the master outdoor unit is started first, and each slave outdoor unit is
started with a delay of 5s.
4.2 Compressor Startup Delay Control
In initial startup control, compressor startup is delayed for 12 minutes in order to let the master unit search for the indoor
units' addresses. In restart control (except in oil return operation and defrosting operation), compressor startup is delayed
such that a minimum of 7 minutes has elapsed since the compressor stopped, in order to prevent frequent compressor
on/off and to equalize the pressure within the refrigerant system.
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