Protective Control Function - Mitsubishi Heavy Industries SRK20ZJ-S Data Book

12. Protective control function

(1) Frost prevention control (During cooling or dehumidifying)
(a) Operating conditions
) Indoor heat exchanger temperature (Th) is lower than ºC.
)  minutes after reaching the compressor command speed except 0 rps.
(b) Detail of anti-frost operation
Indoor heat exchanger
Item
Lower limit of compressor command speed
Indoor fan
Outdoor fan
4-way valve
Notes (1) When the indoor heat exchanger temperature is in the range of 2.5~5ºC, the speed is reduced by 4 rps at each 20 seconds.
() When the temperature is lower than .ºC, the compressor is stopped.
(3) When the indoor heat exchanger temperature is in the range of 5~8ºC, the compressor command speed is been maintained.
(c) Reset conditions: When either of the following condition is satisfied.
) The indoor heat exchanger temperature (Th) is ºC or higher.
) The compressor command speed is 0 rps.
(2) Cooling overload protective control
(a) Operating conditions: When the outdoor air temperature (TH) has become continuously for 0 seconds at ºC or
(b) Detail of operation
) The outdoor fan is stepped up by  speed step. (Upper limit th speed.)
) The lower limit of compressor command speed is set to 0 or 0 rps and even if the calculated result becomes lower than that
after fuzzy calculation, the speed is kept to 0 or 0 rps. However, when the thermo becomes OFF, the speed is reduced to 0
rps.
(c) Reset conditions: When either of the following condition is satisfied.
) The outdoor air temperature is lower than 0ºC or ºC.
) The compressor command speed is 0 rps.
(3) Cooling high pressure control
(a) Purpose: Prevents anomalous high pressure operation during cooling.
(b) Detector: Outdoor heat exchanger sensor (TH)
(c) Detail of operation:
(Example) Fuzzy
Notes (1) When the outdoor heat exchanger temperature is in the range of 58~63ºC, the speed is reduced by 6 rps at each 30 seconds.
() When the temperature is ºC or higher, the compressor is stopped.
(3) When the outdoor heat exchanger temperature is in the range of 53~58ºC, if the compressor command speed is been maintained and the operation has
continued for more than 0 seconds at the same speed, it returns to the normal cooling operation.
temperature 5°C or lower
 rps
Depends on operation mode
Depends on command speed
OFF
more, or ºC or more with the compressor running, the lower limit speed of compressor is
brought up.
Item
Outdoor air temperature
Lower limit speed
After lapse of 30 sec. or over
After lapse of 30 sec. or over
After lapse of 30 sec. or over
53
Outdoor heat exchanger temperature (°C)
2.5°C or lower
0 rps
Protects the fan tap just before
frost prevention control
Depends on stop mode
Model
SRK20~35ZJ-S
°C or more
0 rps
6rps (1)
(3)
6rps (1)
(3)
lower limit
(3)
speed 30 rps
58 63

- -
'09•SRK-DB-087D
compressor
command
speed
Lower
limit
speed
0 rps
2.5 5
Indoor heat exchanger
temperature (ºC)
°C or more
0 rps
0rps
8