Main Protection - Midea MSMBA-07HRN1 Service Manual

Mission On-off DM16-01.01.21en

9.3 Main Protection

7.3.1 Time Delay at restart for compressor.
st
Less than 1 minute delay for the 1 time start-up and 3 minutes delay for others.
9.3.2 Sensor protection at open circuit and breaking disconnection.
9.3.3 Zero crossing detection error protection
If AC cannot detect zero crossing signal for 4 minutes or the zero crossing signal time interval is not
correct, the unit will stop and the LED will display the failure. The correct zero crossing signal time
interval should be between 6-13ms.
9.3.4 Fan Speed is out of control
When Indoor Fan Speed is too low(lower than 300RPM) lasting 2 minutes, the unit stops and LED
displays failure information and can't returns to normal operation automatically.
9.3.5 Current protection
A
B
C
Resume
The current exceeds setting value for certain time, the compressor and outdoor fan will shut off.
9.3.6 Indoor fan delayed open function
When the unit starts up, the indoor fan will open 4s later. If the unit runs in heating mode, the indoor fan
will be also controlled by anti-cold wind function.
9.3.7 Refrigerant leakage detection
This function is only active in cooling mode. It can better prevent the compressor being damaged by
refrigerant leakage or compressor overload.
Open condition:
When compressor is active, the value of the Coil temperature of evaporator T2 has no change or very
little change.
36 Service manual