Refrigerant Recovery Control; Outdoor Unit Fan Control - Mitsubishi Electric HP120TNU-A Service Handbook

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

Refrigerant Recovery Control

Refrigerant recovery is performed for each BC port during heating operation to prevent the refrigerant from accumulating in-
side the units that are stopped (in the fan mode), in the cooling mode, or in the heating Thermo-OFF mode.
It is also performed during cooling operation to prevent an excessive amount of refrigerant from accumulating in the outdoor
heat exchanger.
Starting criteria for the refrigerant recovery cycle (during Cooling-only, Cooling-main, Heating-only, or Heating-main
mode)
The refrigerant recovery mode starts when all of the following conditions are met:
1) When 5 minutes have passed in the Heating-only or Heating-main mode or 30 seconds have passed in the Cooling-only or
Cooling-main mode since the completion of the previous refrigerant recovery cycle AND the when following conditions are
met.
TH4 > 105°C [221°F]
2) When the port is not in the 4-minute restart delay mode
Starting criteria for the refrigerant recovery cycle (during Cooling-only, Cooling-main, Heating-only, or Heating-main
mode)
1) When the port is in the cooling Thermo-OFF, fan, or stop mode
SVC at the port turns on for 30 seconds.
2) The opening of LEV1 and LEV3 is increased.
5-2-10

Outdoor Unit Fan Control

(1) Control method
Depending on the capacity required, the rotation speed of the outdoor fan is controlled by the inverter to keep a constant con-
densing temperature (outside temperature + 10°C [50°F]) during cooling operation and a constant evaporation temperature
(0°C [32°F] = 0.71 MPa [103 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.
Both fans operate on the HP72, HP96, and HP120 models of outdoor units.
(3) Outdoor heat exchanger capacity control pattern
Outdoor fan rotation control is supported.
As the operation pattern number increases, the refrigerant bypassing the outdoor heat exchanger increases. As the operation
pattern number increases, the capacity difference becomes smaller between cooling operation and heating operation.
In each mode, the four-way valve and the expansion valve operate as shown in the table below. The expansion valve may
open or close during the refrigerant equalization control or the evaporation temperature control. See [5-2-11 Expansion valve
control (LEV2a, LEV2b, and LEV2d)]
Model
HP72, HP96,
HP120 models
*During the liquid-balance operation in a system with combined units, the opening of LEV2d may fluctuate, but never goes
beyond the value listed, to maintain a constant ratio of openings between LEV2d and LEV2a.
HWE18220_GB
Operation Operation
mode patterns
21S4a
Cooling-only 1
Cooling-main
2
3
4
Heating-only 1
Heating-main 1
2
Defrost 1
Four-way valve
21S4b 21S4c LEV2a
OFF OFF - 3000
OFF ON - 3000
OFF ON - 3000
OFF ON - 1000
ON ON - 3000
ON ON - 3000
ON ON - 3000
OFF OFF - 3000
LEV
LEV2b LEV2c LEV2d
3000 - 20
41 - 800
41 - 6000
41 - 6000
3000 - 20
3000 - 20
3000 - 1000*
3000 - 20
19
chapter 5 -