M thermal Mono
202004 25
6 Special Control
6.1 Oil Return Operation
In order to prevent the compressor from running out of oil, the oil return operation is conducted to recover oil that has
flowed out of the compressor and into the refrigerant piping. When the oil return operation is being conducted, the
outdoor unit refrigerant system main PCB displays code d0.
Timing of oil return operation:
When the compressor cumulative operating time with running rotation speed less than 42rps reaches 6 hours.
The oil return operation ceases when any one of the following three conditions occurs:
Oil return operation duration reaches 5 minutes.
Compressor stops.
Mode change command is received.
Tables 3-6.1 show component control during oil return operation in cooling mode.
Table 3-6.1: Outdoor unit component control during oil return operation in cooling mode
Control functions and states
Runs at oil return operation rotation speed
Controlled according to outdoor heat exchanger pipe
temperature
Electronic expansion valve
Tables 3-6.2 show component control during oil return operation in heating and DHW modes.
Table 3-6.2: Outdoor unit component control during oil return operation in heating and DHW modes
Control functions and states
Runs at oil return operation rotation speed
Controlled according to outdoor heat exchanger pipe
temperature
Electronic expansion valve
6.2 Defrosting Operation
In order to recover heating capacity, the defrosting operation is conducted when the outdoor unit air side heat exchanger
is performing as a condenser. The defrosting operation is controlled according to outdoor ambient temperature, air side
heat exchanger refrigerant outlet temperature and the compressor running time.
Table 3-6.3: Component control during defrosting operation
Control functions and states
Runs at defrosting operation rotation speed
Electronic expansion valve
6.3 Fast DHW Operation
Fast DHW operation is used to quickly meet a requirement for domestic hot water when DHW priority has been set on the
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