Mitsubishi Electric PFAV-P250VM-E Service Manual page 106

[ VIII Control ]
-9- Capacity Control of Outdoor Fan
(1) Control method
Depending on the capacity required, the rotation speed of the outdoor unit fan is controlled by the inverter to keep a constant
condensing temperature during cooling operation and a constant evaporation temperature during heating operation.
The OS in the multiple-outdoor-unit system operates at the actual outdoor unit fan control value that is calculated by the OS
based on the preliminary outdoor unit fan control value that the OC determines.
(2) Control
Outdoor unit fan stops while the compressor is stopped (except in the presence of input from snow sensor).
The fan operates at full speed for 5 seconds after start-up.(Only when TH7<0°C [32°F])
The outdoor unit fan stops during defrost operation.
-10- Subcool Coil Control (Linear Expansion Valve <LEV1>)
The OC and OS control the subcool coil individually.
The LEV is controlled every 30 seconds to maintain constant the subcool at the outdoor unit heat exchanger outlet that is
calculated from the values of high pressure (63HS1) and liquid piping temperature (TH3), or the superheat that is calculated
from the values of low pressure (63LS) and the bypass outlet temperature (TH2) of the subcool coil.
LEV opening is controlled based on the values of the inlet (TH6) and the outlet (TH3) temperatures of the subcool coil, high
pressure (63HS1), and discharge temperature (TH4). In a single-outdoor-unit system, the LEV is closed (0) in the heating
mode, while the compressor is stopped, and during cooling Thermo-OFF. In a multiple-outdoor-unit system, the LEV closes
(0) during heating operation, while the compressor is stopped, or during cooling Thermo-OFF. The LEV opens to a specified
position when 15 minutes have passed after Thermo-OFF. (65 pulses)
During defrost, normally, the valve is initially set at 0 pulse, although it may operate at higher pulses depending on the 63 LS
and TH4 status.
-11- Refrigerant flow control (Linear expansion valve <LEV2>)
Refrigerant flow is controlled by each unit in the combined models during heating. Refrigerant flow control is performed by the
OC and OS individually. The valve opens to a specified angle during cooling (Opening: 2100 pulses)
Valve opening is controlled based on the values of high pressure (63HS1), discharge temperature (TH4), low pressure(
63LS), and piping temperature (TH5).
The valve moves to the predetermined position while the unit is stopped.
The valve opening may increase to 3000 pulses during the defrost cycle or when the units are operated in unusual operating
conditions.
-12- Control at Initial Start-up
When started up for the first time before 12 hours have elapsed after power on, the unit goes into the initial startup mode.
At the completion of the initial operation mode on the OC and OS, they will go into the normal control mode.
1. Flowchart of initial operation
(1) Outdoor unit P250 model
HWE10190
Initial startup mode starts.
50 F 60Hz
Completed in the integrated operation time of 35 minutes.
or F < 50Hz
Completed in the integrated operation time of 90 minutes.
Initial startup mode complete
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