Outdoor Unit Fan Control; Subcool Coil Control (Linear Expansion Valve <Lev1>); Refrigerant Flow Control (Linear Expansion Valves <Lev2A And Lev2B>); Control Of Controller Cooling Function (Electronic Expansion Valve <Lev9>) - Mitsubishi Electric PUHY-P250YNW-A Service Handbook

[5-2 Outdoor Unit Control ]
5-2-8

Outdoor Unit Fan Control

(1) Control method
Depending on the capacity required, the rotation speed of the outdoor unit fan is controlled by the inverter, targeting a constant
evaporation temperature of (0°C [32°F]= 0.71 MPa [103 psi]) during cooling 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])
5-2-9 Subcool Coil Control (Linear Expansion Valve <LEV1>)
The OC and OS controls 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) during cooling
Thermo-OFF. In a multiple-outdoor-unit system, the LEV closes (0) during cooling Thermo-OFF.
5-2-10 Refrigerant Flow Control (Linear Expansion Valves <LEV2a and LEV2b>)
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 units are operated in unusual operating conditions.
5-2-11 Control of Controller Cooling Function (Electronic Expansion Valve <LEV9>)
Control of controller cooling function is performed individually for OC and OS.
The opening of LEV9 is adjusted every three seconds to keep the controller heatsink temperature (THHS) below the threshold
value, which is determined by the setting of the outside temperature (TH7).
5-2-12

Control at Initial Startup

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) P250YNW model
12
- chapter 5
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.
or the discharge superheat (TH4 - Tc) is detected (within
5 minutes of startup) that remains above approximately
25 degrees for one minute or if the shell bottom SH
(TH15-Te) is 15 deg or above (for continuous 5 minutes)
10 minutes after start up.
Initial startup mode complete
BS_05_C