Protection - Midea MSX-18HRDN1-QC2 Service Manual

9.3 Protection

9.3.1 Three Minutes Delay at restart for compressor.
9.3.2 Temperature protection of compressor top.
9.3.3 If the temperature of compressor top is too high(higher than 115℃ and the Over-load Protector is cut, the units
stop. When the Over-load Protector restore and close(lower than 100℃), the compressor will restart( in this case
the compressor is restricted by Three Minutes Delay protection.
9.3.4 Temperature protection of compressor exhaust.
If the exhaust temp. of compressor is higher than 115℃ and lasts for 5 seconds, the compressor stops and does
not resume until the exhaust temp. is lower than 90℃.
9.3.5 Inverter module Protection, Inverter module Protection itself has a protection function against current, voltage and
temperature. If these protections happened, the corresponding code will display on indoor unit LED.
9.3.6 Sensor protection at open circuit and breaking disconnection
9.3.7 Fan Speed is out of control. When Indoor Fan Speed is too low (lower than 300RPM for 60 seconds), the unit
stops and LED displays failure information and can't return to normal operation automatically.
9.3.8 Cross Zero signal error warning. If there are 20 alternations of Cross Zero signals are incorrect, the unit stops and
LED displays failure information. After resuming, the motor rotates again. The spacing of Cross Zero signal is
6-13ms.
9.3.9 Indoor fan delayed open function
9.3.10 For all modes, when the units are turned on, the indoor fan can operate 10 seconds after the action of louver.
9.3.11 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.
9.3.12 Compressor heating cable
If outdoor temperature is lower than 5℃, the compressor heating cable begins to work. If outdoor temperature is
This indicator appears only when the compressor is in operation
and indicates the current operating frequency.
Usually it displays the temperature settings. When the setting
temperature is being changed, this indicator will flash at 0.5Hz
for 10 times. It displays the room temperature (0℃~50℃) when
the air conditioner is in FAN only operation. When the unit stops
operation, it returns to original factory settings.
It also displays the malfunction code or protection code.
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