Mitsubishi Electric PUHY-P120YHMU-A, Service Manual

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[
VII
Control ]
- 101 - HWE0804A GB
(2) During cooling operation
Starting refrigerant recovery mode
The refrigerant recovery mode starts when all the following conditions are met:
Œ
30 minutes have passed since the completion of previous refrigerant recovery.
Œ
When the unit keeps running for 3 minutes in a row or more with high discharge temperature
Œ TH4 > 105°C [221°F] or 63HS1 > 3.43 MPa [497 psi] (35 kg/cm
2
G) and SC0 > 10°C [18°F]
Refrigerant recovery
The opening of LEV1 is increased and periodic control begins again.
-9- Capacity Control of Outdoor Fan
(1) Control method
Œ
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 and constant condensing temperature
of (49°C [120°F]= 2.88 MPa [418 psi]) during heating operation.
ΠThe 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
ΠOutdoor unit fan stops while the compressor is stopped (except in the presence of input from snow sensor).
Œ The fan operates at full speed for 5 seconds after start-up.(Only when TH7<0°C [32°F])
Œ
The outdoor unit fan stops during defrost operation.
-10- Subcool Coil Control (Linear Expansion Valve <LEV1>)
ΠThe OC, OS1, and OS2 controls the subcool coil individually.
ΠThe 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.
ΠLEV 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)
ΠThe valve remains open at the preset position. (480 pulses)
-11- Refrigerant flow control (Linear expansion valve <LEV2a, LEV2b>)
ΠRefrigerant 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: 1400 pulses)
Œ
Valve opening is controlled based on the values of high pressure (63HS1), discharge temperature (TH4), low pressure(
63LS), and piping temperature (TH5).
Œ
The valve moves to the predetermined position while the unit is stopped.
Œ
The valve remains open at the preset position. (1400 pulses)
-12- Control at Initial Start-up
Œ
When started up for the first time before 12 hours have elapsed after power on, the unit goes into the initial startup mode.
Œ
At the completion of the initial operation mode on the OC, OS1, and OS2, they will go into the normal control mode.
1. Flowchart of initial operation
(1) P72, P96, P120 models
50 F 60Hz
or F < 50Hz
Initial startup mode starts.
Completed in the integrated operation time of 35 minutes.
Initial startup mode complete
Completed in the integrated operation time of 90 minutes.