Mitsubishi Electric City Multi PFAV-P500VMH-E, Service Handbook

Page: 85 / 242

[
VIII
Control ]
- 76 -
HWE07150 GB
(2) During cooling operation
Starting refrigerant recovery mode
The refrigerant recovery mode starts when all the following conditions are met:
Π30 minutes have passed since the completion of previous refrigerant recovery.
ΠWhen 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. (Periodic control begins after 30 seconds)
-9- Capacity Control of Outdoor Fan and Heat Exchanger
(1) Control method
ΠDepending on the capacity required, the rotation speed of the outdoor unit fan is controlled by the inverter, targeting an evap-
oration temperature during cooling operation and condensing temperature 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).
ΠThe fan operates at full speed for 5 seconds after start-up.
ΠThe outdoor unit fan stops during defrost operation.
-10- Subcool Coil Control (Linear Expansion Valve <LEV1>)
ΠThe OC and OS 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 multiple-outdoor-unit system, the LEV closes (0) during heating op-
eration, while the compressor is stopped, or during cooling Thermo-OFF. The LEV opens to a specified position when 15 min-
utes 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 and OS individually. The valve opens to a specified angle during cooling (Opening: 1400 pulses)
ΠValve opening is controlled based on the values of high pressure (63HS1), discharge temperature (TH4), low pressure(
63LS), and piping temperature (TH5).
ΠThe valve moves to the predetermined position while the unit is stopped.
ΠThe valve remains open at the preset position. (1400 pulses)
-12- Control at Initial Start-up
ΠWhen started up for the first time before 12 hours have elapsed after power on, the unit goes into the initial startup mode.
ΠAt the completion of the initial operation mode on the OC and OS, they will go into the normal control mode.