Mitsubishi Electric PURY-P72 Service Handbook page 145

[ VII Control ]
(3) Stopping the defrost operation
The defrost cycle ends when 12 minutes have passed since the beginning of the cycle, or when the pipe temperature (TH3
and TH6) has been continuously detected for 2 minutes that exceeds the values in the table below
Defrost operation will not stop its operation for 4 minutes once started.
In the multiple-outdoor-unit system, defrosting is stopped on all units at the same time.
Model
P72 model
P96 model
P120 model
(4) Problems during defrost operation
If a problem is detected during defrost operation, the operation will be stopped, and the defrost prohibition time based on the
integrated compressor operation time will be set to 20 minutes.
(5) Change in the number of operating indoor units during defrost operation
Even when there is a change in the number of operating indoor units during defrost operation, the operation will continue, and
an adjustment will be made after the completion of the defrost operation.
Defrost operation will be continued, even if the indoor units stop or under the Thermo-OFF conditions until it has run its course.
-8- 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
SV C at the port turns on for 30 seconds. (
2) The opening of LEV1 and LEV3 is increased.
-9- Capacity Control of Outdoor Fan and Heat Exchanger
(1) Control method
Depending on the capacity required, the rotation speed of the outdoor unit fan is controlled by the inverter to keep a constant
condensing temperature of (outside temperature +10°C [50°F]) during cooling operation and a constant evaporation temper-
ature of (0°C [32°F] =0.71 <Pa [103psi]) 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.
HWE0803A
TH3
SW3 - 3 OFF
10°C [50°F]
7°C [45°F]
7°C [45°F]
indicates port No.)
- 136 -
SW3 - 3 ON
15°C [59°F]
12°C [54°F]
12°C [54°F]
GB