Midea MCD-18HRFN1-QRC4 Service Manual page 103

Electrical Control Function
1. Electrical Control Function
1.1 Definition
T1: Indoor room temperature
T2: Coil temperature of indoor heat exchanger middle.
T2B: Coil temperature of indoor heat exchanger outlet.
T3: Coil temperature of condenser
T4: Outdoor ambient temperature
T5: Compressor discharge temperature
1.2 Main Protection
1.2.1 Time delay at restart for compressor.
1.2.2 Temperature protection of compressor top
The unit will stop working when the compressor top temp. protector cut off, and will restart after the
compressor top temp. protector restart.
1.2.3 Temperature protection of compressor discharge
For 12K units:
When the compressor discharge temp. is getting higher, the running frequency will be limited as below rules:
---Compressor discharge temp. T5>115℃ for 5s, compressor stops and restarts up till T5<90℃
---110<T5<115℃, decrease the frequency to the lower level every 2 minutes.
---105<T5<110℃, keep running at the current frequency.
----T5<105℃, no limit for frequency.
For other units:
When the compressor discharge temp. is getting higher, the running frequency will be limited as below rules:
----If 102℃<T5<115℃, decrease the frequency to the lower level every 2 minutes till to F1.
---If T5>115℃ for 10 seconds, the compressor will stop and restart till T5<90℃.
1.2.4 Sensor protection at open circuit and breaking disconnection.
1.2.5 Indoor fan delayed open function
When the unit starts up, the louver will be active immediately and the indoor fan will open 10s later.
If the unit runs in heating mode, the indoor fan will be also controlled by anti-cold wind function.
1.2.6 Fan Speed is out of control(for units used DC motor)
When Indoor Fan Speed keeps too low (For less than less than
Super slim cassette, 200RPM, for other models,
) for 50s, the unit will stop and the LED will display the failure
300RPM
Electrical Control System 109