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>); Injection Control (Linear Expansion Valve <Lev4>) - Mitsubishi Electric PUHY-HP72 Service Handbook

[5-2 Outdoor Unit Control ]
5-2-11 Subcool Coil Control (Linear Expansion Valve <LEV1>)
The OC, OS1, and OS2 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) 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 the defrost cycle, normally, the valve initially operates at 0 pulses, although it may operate at higher pulses depending
on the 63LS and TH4 status.
5-2-12 Refrigerant Flow Control (Linear Expansion Valves <LEV2a and LEV2b>)
Refrigerant flow is controlled by each unit in the combined models during heating. Refrigerant flow control is performed by the
OC, OS1, and OS2 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.
5-2-13 Control of Controller Cooling Function (Electronic Expansion Valve <LEV9>)
Control of controller cooling function is performed individually for OC, OS1, and OS2.
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).
5-2-14 Injection Control (Linear Expansion Valve <LEV4>)
LEV4 opening is adjusted every 30 seconds to keep the discharge temperature (TH4) within the predetermined range.
Injection control starts when the outside temperature (TH7) drops below 3°C (37.4°F).
5-2-15

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, OS1, and OS2, they will go into the normal control mode.
(1) HP72 - HP120T(Y)NU models
HWE18240_GB
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
17
chapter 5 -