Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 202

SCM-HG (2 room)
(f) Low Hz continuous operation protection control
The following controls are performed to return oil to the compressor when the outdoor unit speed of 28 rps or more to 40 rps
or less is continuously operated for 20 minutes.
1) The decision speed is forced to operate at 40 rps for 2 minutes.
2) The outdoor fan and electronic expansion valve are operated according to the outdoor unit speed.
3) If there is an instruction exceeding 40 rps during this forced 40 rps operation, this control ends and the operation
follows that instruction.
(g) Heating low temperature protection control
The following controls are performed when the outdoor unit is in heating operation at a speed other than 0 rps and the
outdoor temperature is 2 °C or less for 1 continuous minute.
1) The outdoor unit fan speed is forced to 5th speed.
This control is ended when the outdoor temperature reaches 4 °C or more.
2)
(h) Current safe control
1) When converter in port current is detected at the current sensor (CT) and it exceeds the set amperage, the speed is reduced
2 rps. This is rechecked after one second and if it still exceeds the set amperage, the speed is reduced another 2 rps.
2) If the actual speed operated at 28 rps or less, the inverter is stopped. It is restarted after a 3 minute delay. However, if it
is restarted repeatedly within an interval of 1 hour, it will not start on the fifth time.
(i) Current cut
This detects converter output current at the shunt resistor and if it exceeds the set value, the inverter is stopped. It is restarted
after a 3 minute delay. However, if the current cut operates again when the actual speed is less than 20 rps, it will not start on
the fourth time.
(j) Compressor overheat protection
The detection temperature of the compressor dome thermistor (Tho-D) is used to prevent oil deterioration and damage to the
motor wire due to overheating of the compressor.
1) If Tho-D becomes
restarted when Tho-D becomes < 95 °C. However, if it is restarted repeatedly within an interval of 1 hour, it will not
start on the third time.
When 105 °C
2)
Decision speed
Inverter
Notes (1) If the temperature of the compressor dome is 105 °C or more and less than 125 °C, the outdoor unit speed is reduced by 8 rps.
(2) After 20 seconds, if the temperature of the compressor dome has decreased, it is lowered 2 rps. If the temperature has risen or is
(3) If the temperature of the compressor dome is 95 °C or more and less than 105 °C, the speed of the outdoor unit is maintained. If
(k) Serial transmission abnormality protection
If the compressor is operating with an outdoor speed other than 0 rps and a serial signal cannot be received from all indoor
controls with outdoor controls having serial signals other than "stop - 0 rps" continuously for 1 minute and 55 seconds, the
inverter is stopped.
After the inverter has been stopped, it will be restarted after the compressor start delay if a serial signal can be received again
from the indoor control.
200
125 °C, the inverter is stopped. After the stop mode has been activated, the inverter will be
Tho-D < 125 °C, the following outdoor unit speed controls are performed.
6 minutes of more has passed
6 minutes of more has passed
6 minutes of more has passed
95
Compressor doom temperature (°C)
the same, it is lowered another 8 rps.
operation is maintained at the same speed for 6 minutes or more or if the temperature is 95 °C or less, control is returned to
normal operation.
(3)
8 rps
(3) 8 rps or 2 rps
(3)
Lower limit 28 rps 8 rps or 2 rps
0 rps
105 125
(2)
(2)