Protective Control Function - Mitsubishi Heavy Industries SRK20ZD-S1 Technical Manual

(11) Protective control function

(a) Frost prevention for indoor heat exchanger (During cooling or dehumidifying)
(i) Operating conditions
1) Indoor heat exchanger temperature (detected with Th2) is lower than 2.5ºC.
2) 3 minutes elapsed after the start of operation.
(ii) Detail of anti-frost operation
Compressor
Indoor fan
Outdoor fan
4-way valve
(iii) Reset conditions: Indoor heat exchanger temperature (Th2) is higher than 8ºC.
(b) Indoor fan motor protection
When the air conditioner is operating and the indoor fan motor is turned ON, if the indoor fan motor has operated at 300 rpm or
under for more than 30 seconds, the unit enters first in the stop mode and then stops the entire system.
Timer light illuminates simultaneously and the operation lamp flashing 6 times at each 8-second.
(c) Dew condensation prevention control for cooling operation
This prevents dew condensation, in the indoor unit, from occurring.
(i) Operating condition: when compressor is kept ON for 30 min. after the unit starts operation.
(ii) Operation content: forces the indoor fan to change from Speed 1 to Speed 2.
(iii) Resetting condition: When compressor is off, or when dew condensation prevention control has been operating continu-
ously for 30 minutes.
(d) Three-minute forced operation
When the compressor begins operating the thermal operation is not effective for 3 minutes, so operation continues as is in the
operation mode. (After 3 minutes has passed the thermal operation is effective.)
However, stopping the compressor via a stop signal or protection control has priority.
(e) High-pressure control
The indoor heat exchanger sensor detection temperature controls the outdoor fan and compressor.
¡ When the indoor heat exchanger
temperature is = > 58˚C
Outdoor fan
Indoor heat exchanger temp. (˚C)
(f) 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.
OFF
1st speed
OFF
Stop mode
ON
OFF
48 58
¡ When the indoor heat exchanger
temperature is = > 62˚C
Compressor
Indoor heat exchanger temp. (˚C)
160
- -
ON
OFF
48 62