Refrigerant Recovery Control; Outdoor Unit Fan Control - Mitsubishi Electric PUHY-HP72 Service Handbook

[5-2 Outdoor Unit Control ]
5-2-9

Refrigerant Recovery Control

Recovery of refrigerant is performed during heating operation to prevent the refrigerant from accumulating inside the unit while
it is stopped (unit in fan mode), or inside the indoor unit that is in cooling mode or in heating mode with thermo off.
It is also performed during cooling operation to prevent an excessive amount of refrigerant from accumulating in the outdoor
heat exchanger.
(1) During heating operation
Starting refrigerant recovery mode
The refrigerant recovery mode in heating starts when all of the following three conditions are met:
15 minutes have passed since the completion of previous refrigerant recovery.
TH4 > 115°C [239°F]
Frequencies below 50 Hz
Refrigerant recovery
1) Refrigerant is recovered with the LEV on the applicable indoor unit (unit under stopping mode, fan mode, cooling, heating with
thermo off) being opened for 30 seconds.
2) Periodic capacity control of the outdoor units and periodic LEV control of the indoor units will be suspended during refrigerant
recovery operation; they will be performed after the recovery has been completed.
(2) During cooling operation
Starting refrigerant recovery mode
The refrigerant recovery mode starts when all the following conditions are met:
30 minutes have passed since the completion of previous refrigerant recovery.
When the unit keeps running for 3 minutes in a row or more with high discharge temperature
TH4 > 105°C [221°F] or 63HS1 > 3.43 MPa [497 psi] (35 kg/cm
Refrigerant recovery
The opening of LEV1 is increased and periodic control begins again.
5-2-10

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 and constant condensing temperature
of (49°C [120°F]= 2.88 MPa [418 psi]) 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.
16
- chapter 5
Opening of LEV during refrigerant recovery
Opening of indoor unit LEV: 400 pulses
Initial opening of LEV
30 seconds
Start
Finish
2
G) and SC0 > 10°C [50°F]
HWE18240_GB