Mitsubishi Heavy Industries SCM71ZM-S1 Technical Manual page 199

(7) Refrigeration cycle system protective control
(a) Starting condition: This control starts when the following conditions are satisfied.
(i) When it has elapsed 30 minutes after the compressor was changed from OFF to ON in the cooling operation mode
for more than 5 minutes.
(ii) When the compressor command speed has satisfied the following conditions.
(iii) When the indoor air temperature of running indoor unit (Th1) and the indoor heat exchanger temperature (Th2) have
satisfied the following condition even on one unit.
Compressor
Unit
command speed
40 rps
1
50 rps
2
60 rps
3
70 rps
4
80 rps
5
90 rps
6
(b) Contents of control
(i) Stop the compressor and delay the start, and then restarts.
(ii) Compressor stops by the abnormal stop when the compressor stop has occurred 3 times in one hour.
(8) Crankcase heater
(a) Operating conditions: This control starts when all the conditions below are satisfied.
(i) After the operation mode is changed to stop and the compressor command speed becomes 0 rps continuously for 30 minutes.
(ii) When the temperature detected by the outdoor air temperature (Tho-A) is -2°C or lower after the compressor stops.
(b) Detail of operation
The crankcase heater operates, warming up the compressor, then refrigerant begins circulating smoothly when the air-con-
ditioner starts its heating operation, and heating begins.
(c) Restoration conditions
When the temperature detected by the outdoor air temperature (Tho-A) reaches 0°C or higher, or the operation mode
changes from stop to cooling or heating.
(9) Inching prevention
When the compressor becomes to the thermo operation within 5 minutes since operation start or becomes dehumidifying opera-
tion, the operation is continued with the compressor command speed of minimum rps forcibly.
Indoor air temperature Indoor air temperature (Th1) and indoor
(Th1, ℃ )
heat exchanger temperature (Th2)
10 < = Th1 < = 40
198
-
Th1 - 4 < Th2
Th1 - 3 < Th2
Th1 - 2 < Th2
-
'17 • SCM-T-225
Duration
5 minute