Mitsubishi SCM80ZA Manual page 33

(d) Low Hz continuous operation protection control
The following controls are performed to return the oil to the compressor when the outdoor frequency is less than 34 Hz and
other than 0 Hz for 20 continuous minutes or more.
1) Forced operation at outdoor frequency of 34 Hz is performed for 1 minute.
2) The outdoor fan operates according to decision frequency and the expansion valve operates according to the outdoor
frequency.
3) If the unit receives a command of that is higher than 34 Hz when operating at the forced 34 Hz, it will respond to the
higher command and the operation of this control is ended.
(e) High Hz continuous operation protection control
The following controls are performed to protect the compressor when the outdoor frequency is 106 Hz or higher for 9
continuous minutes or more.
1) Forced operation at outdoor frequency of 104 Hz is performed for 1 minute.
2) The outdoor fan operates according to decision frequency and the expansion valve operates according to the outdoor
frequency.
3) If the unit receives a command of that is lower than 104 Hz when operating at the forced 104 Hz, it will respond to the
higher command and the operation of this control is ended.
(f) Heating low temperature protection control
The following controls are performed during heating operation when operating at an outdoor frequency other than 0 Hz and
the temperature detected by the outdoor air temperature thermistor is 2°C or less for 1 continuous minute.
1) The fan speed of the outdoor unit is forced one speed higher.
2) When the outdoor air temperature thermistor reaches 4°C or more, the operation of this control is ended.
(g) Inching protection control
1) When the detected outdoor air temperature (detected by Tho-A) before the compressor stop is 22°C or less for the
cooling operation and 0°C or less for the heating operation for 1 continuous minute, following control is executed in
order to prevent the dilution of the refrigerant oil due to the dissolved refrigerant caused by the frequent start/stop of the
compressor during the therm operation.
Decision frequency
Outdoor frequency
Hot Standby
2) Restoration is made when the outdoor air temperature thermistor detects a temperature of 24°C or more during cooling
or a temperature of 2°C or more during heating.
(h) Current safe control
1) When the converter input current detected by the current sensor (CT) exceeds the set value, the frequency is reduced by
2 Hz. Checks are performed every second following this and if the current still exceeds the setting, the frequency is
reduced by another 2 Hz.
2) When the frequency is 30 Hz or less, this control will operate four in one hour and then perform an abnormal stop. At the
same time, LED 5 on the printed circuit board for the outdoor unit will flash 3 times at 0.5 second intervals every 8
seconds. Note that on the first operation, the unit can be restarted after setting the compressor to stop mode.
(i) Current cut
An abnormal stop is made if the converter output current at the shunt resistor exceeds the set value. At the same time, LED 5
on the printed circuit board for the outdoor unit will flash 1 time at a 0.5 second interval every 8 seconds.
The unit is re-started after the stop mode, however, if the current cut has been operated 3 times at less than 30 Hz, the fourth
start cannot be performed. (The timer lamp on the indoor unit will flash 1 time.)
0 Hz
ON
OFF
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Stop mode
1 minute 55 seconds
1 minute
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