Mitsubishi Heavy Industries SRK20HC-S Technical Manual page 21

(5) High-pressure control
The indoor heat exchanger thermistor detection temperature controls the outdoor fan and compressor.
¡ When the indoor heat exchanger
temperature Is
Outdoor fan
Indoor heat exchanger temp. (˚C)
(6) Current Cut
If current that is higher than the set current flows for 0.5 second continuously, the current to the compressor is cut off. After a 3-
minute delay, if the current is 1.5 ~ 2 A or less, the compressor restarts, but if the overcurrent is detected 5 times within 60 minutes
after it is detected the first time, it results in an abnormal stop. Also, if the overcurrent continues for 60 minutes, it results in an
abnormal stop.
(7) Compressor Overheat Protection
If the discharge pipe temperature (sensed by Tho-D) exceeds the set temperature value, the compressor stops. If the temperature is 95ºC
or lower after a 3-minute delay, it starts again, but if this function is reactivated again within 60 minutes, it results in an abnormal stop.
(8) Serial signal transmission error protection
(a) Purpose: Prevents malfunction resulting from error on the indoor ↔ outdoor signals.
(b) Detail of operation: When the indoor unit controller ↔ outdoor unit controller signals cannot be received, the compressor
is stopped immediately. Simultaneously, the red LED on the printed circuit board of outdoor unit controller flashing 6 times
for 0.5 second at intervals of 8 seconds. Once the operation stops, it does not start any more.
(Timer lamp on the indoor unit flashing at the same time.)
(9) Thermistor disconnection (room temperature, indoor heat exchanger, outdoor temperature, discharge pipe)
(a) Room temperature thermistor
If the temperature detected by the room temperature thermistor is –20ºC or lower continuously for 15 seconds or longer while
operation is stopped, an error indication is displayed.
(b) Indoor heat exchanger thermistor
If the temperature detected by the indoor heat exchanger thermistor is –20ºC or lower continuously for 15 seconds or longer
while operation is stopped, an error indication is displayed.
Also, if the temperature detected by the indoor heat exchanger thermistor is –20ºC or lower continuously for 3 minutes after
heating operation has started, the indoor unit's fan speed is forcibly raised to speed 5. After this, the air conditioner is stopped
if the detected temperature remains at –20ºC continuously for 40 minutes.
(c) Outdoor heat exchanger thermistor
If the temperature detected by the outdoor heat exchanger thermistor is –50ºC or lower continuously for 15 seconds or longer
while operation is stopped, an error indication is displayed.
Also, the air conditioner is stopped if the temperature detected by the outdoor heat exchanger thermistor remains at –50ºC or
lower continuously for 40 minutes after heating operation has started.
(d) Outdoor temperature thermistor
If the temperature detected by the outdoor temperature thermistor is –40ºC or lower continuously for 15 seconds or longer
while operation is stopped, an error indication is displayed.
(e) Discharge pipe thermistor
After the compressor ha operated for 9 minutes continuously, if there is a disconnected signal for the discharge pipe ther-
mistor detected temperature for 10 seconds (less than 7ºC), the compressor stops. After a 3-minute delay, it restarts, but if an
abnormality is detected 4 times continuously, the air conditioner is stopped fully and an error indication is displayed.
58˚C
ON
OFF
48 58
Operation possible
95
Discharge pipe temperature (˚C)
¡ When the indoor heat exchanger
temperature Is
Compressor
Indoor heat exchanger temp. (˚C)
Abnormal stop
125
19
- -
62˚C
ON
OFF
48 62