Midea MS9A-09HRDN1-QC2, Service Manual

22

      Pressing “LED display” button on remote controller will turn off all displays on indoor unit, while pressing once 

again, all displays will resume.   

9.3  Protection 

  9.3.1  Protection of compressor top temperature. 

When the Over-load Protector is cut due to too high temperature of compressor top, the unit will stop. When 

the Over-load Protector is closed again due to decreasing of compressor top temperature, the unit will restart( in 

this case the compressor is restricted by Three Minutes Delay protection). 

9.3.2  Protection of discharge temperature (Td). 

      1) Compressor will stop immediately if Td>115  for 5s. 

            2) If 90

≤

Td

≤

115 , compressor will run with restricted frequency. 

            3) If Td<90

℃

, compressor will restart or run without restricted frequency 

9.3.3    Three Minutes Delay at restart for compressor. 

            It will take 3 minutes every time when compressor starts.   

It will take only 1 minute when the unit is powered on at first time. 

9.3.4  Temperature sensor protection at open circuit or short circuit. 

9.3.5    Protection of indoor fan speed. 

  When indoor fan speed is too low (lower than 300rpm for 50 seconds), the unit will stop and LED display error 

code and can’t return

to normal operation automatically. 

9.3.6    Cross Zero signal error warning. 

  If there are no Cross Zero signal or the alternation of Cross Zero signal is not correct, the unit will stop and 

LED display error code . 

    9.3.7  Inverter module Protection. 

Inverter module has a protection function against current, voltage and temperature. If these protections 

happened, the unit will stop and LED display error code . 

  9.3.8  Indoor fan delayed open function. 

                When the unit is turned on at all modes, the indoor fan will operate 10 seconds later than the action of louver. 

9.3.9    Compressor preheating function. 

1)  Preheating permitting condition: 

    If T4(outdoor ambient temperature

)＜

3

℃

  and the machine connects to power supply newly or if T4

＜

3

℃

        and compressor has stopped for over 3 hours, the compressor heating cable will work. 

2) Preheating 

mode: 

        A weak current flows through the coil of compressor from the wiring terminal of compressor, then the   

        compressor is heated without operation. 

3)  Preheating release condition: 

                      If T4

＞

5

℃

  or user turns on the machine and compressor runs, preheating function will stop. 

9.4  Fan-Only Mode 

9.4.1    Temperature setting function is disabled, and no setting temperature display. 

9.4.2    In this mode, the action of louver is the same as in cooling mode.