Midea V4+R Series, Service Manual

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V4+R VRF 50/60Hz
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2 Stop Operation
The stop operation occurs for one of the three following reasons:
1. Abnormal shutdown: in order to protect the compressors, if an abnormal state occurs the system makes a 'stop with
thermo off' operation and an error code is displayed on the digital display.
2. The system stops when the set temperature has been reached.
3. A unit stops when the load demanded by the indoor units decreases and can be handled by fewer outdoor units.
When a unit stops because the load demanded by the indoor units has decreased and can be handled by fewer outdoor
units, the unit's four-way valve remains on until the load demanded by the indoor units increases and the unit is required
to operate. When the whole system stops, all the units' four-way valves turn off.
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 according to outdoor ambient temperature and discharge temperature. When the
outdoor ambient temperature is above 40°C, the crankcase heater is off; when the outdoor ambient temperature is below
35°C, the crankcase heater is controlled according to discharge temperature. Refer to Figures 3-3.1 and 3-3.2.
Figure 3-3.1: Crankcase heater controlled according to outdoor ambient temperature
Figure 3-3.2: Crankcase heater controlled according to discharge temperature
Ambient temperature < 35
o
C Ambient temperature > 40
o
C
Crankcase heater off
Crankcase heater is controlled according to discharge temperature
Discharge temperature < 40
o
C Discharge temperature > 50
o
C
Crankcase heater off
Crankcase heater on