Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 146

SCM-HG (4 room)
(m) Outdoor unit abnormal stop and compressor motor protection
If the air conditioner is operating at an inverter frequency 28 Hz or more and an input current of 1 A or less is detected for 30
continuous seconds or more, a abnormal stop is performed. At the same time, LED 2 on the printed circuit board for the
outdoor unit will flash 2 times at a 0.5 second interval every 8 seconds.
The 3-minute delay is operated once again. However, if the unit is restarted within 1 hour, it cannot be started a third time.
(The timer lamp on the indoor unit will flash 2 times.)
(n) Discharge pipe thermistor interrupt protection
An abnormal stop is made when the inverter frequency is a value other than 0 Hz and the signal of discharge pipe sensor
temperature is interrupted for 10 seconds or more (at less than 7°C) after 10 minutes have passed since the start of compres-
sor operation. The unit cannot be restarted. At the same time, LED 2 on the printed circuit board for the outdoor unit will light
for 4 seconds and go out for 4 seconds. Note that this function is disabled when the Hot Standby is ON. (The timer lamp on
the indoor unit will flash 2 times.)
(o) Power transistor overheat protection
If the thermal switch inside the power transistor is activated, the compressor is stopped immediately. While the unit can be
restarted once temperature of the power transistor has gone down and/or after the 3-minute delay has finished, it cannot be
started a third time if there is an abnormal stop of a restart within 1 hour. At the same time, LED 2 on the printed circuit board
for the outdoor unit will flash 4 times at a 0.5 second interval every 8 seconds. (The timer lamp on the indoor unit will flash
4 times.)
Set value: 110 ± 10°C open / 90°C close
(p) Serial transmission abnormality protection
An abnormal stop is made if the outdoor unit does not receive serial signal commands, other than "Stop: 0 Hz," from all the
indoor controllers continuously for 1 minute and 55 seconds when the compressor is operating at an outdoor frequency of
other than 0 Hz. At the same time, LED 2 on the printed circuit board for the outdoor unit will flash 6 times at a 0.5 second
interval every 8 seconds. (The timer lamp on the indoor unit will flash 6 times.)
The unit can be restarted if serial signal is restored and/or the 3-minute delay has finished.
(q) High pressure abnormality
The unit is stopped if the high-pressure switch for preventing abnormally high pressures is activated. At the same time, LED
2 on the printed circuit board for the outdoor unit will keep flashing. While the unit can be restarted after the stop mode is
used, it cannot be started a third time if there is an abnormal stop of a restart within 1 hour. (The timer lamp on the indoor unit
will flash 2 times.)
Setting value: 2.94 cut out/ 2.35 cut in (30 cut out/ 24 cut in) [MPa (kgf/cm
(r) Compressor overheat protection control
1) If the discharge pipe sensor mounted to the discharge pipe detects a temperature exceeding 125°C, the compressor is
immediately stopped. The unit can be restarted after the discharge pipe temperature has gone down and/or after the stop
mode is used.
However, it cannot be restarted if there is an abnormal stop of a restart within 1 hour.
At the same time, LED 2 on the printed circuit board for the outdoor unit will flash 5 times at a 0.5 second interval every
8 seconds. (The timer lamp on the indoor unit will flash 5 times.)
2) When the detected temperature is 105°C or more and less than 125°C, the frequency control is as shown below.
Decision frequency
Inverter
Notes (1) If the discharge pipe temperature is 105°C or more and less than 125°C, the frequency is lowered 4 Hz.
(2) After 20 seconds, if the discharge pipe temperature is lower than the previous temperature, the frequency is lowered 2 Hz; if it is higher, the
frequency is lowered 4 Hz.
(3) If the discharge pipe temperature is 95°C or more and less than 105°C and the inverter frequency is maintained and/or the unit operates at the
same frequency for 6 minutes or more, compressor overheat protection control is performed and the unit returns to normal operation.
(4) If there is a lower decision frequency during compressor overheat protection control, the lower frequency is used.
144
6 minutes or more has passed
6 minutes or more has passed
(3)
6 minutes or more has passed
4 Hz up
95
Discharge pipe temperature (°C)
2
)]
4 Hz
(3)
4 Hz or 2 Hz
(3)
Lower limit 28 Hz
4 Hz or 2 Hz
(3)
0 Hz
105 125
(2)
(2)