Midea MUE-48CRN1-RB4, Service Manual

Page: 236 / 264

Electrical Control Function
232 Electrical Control
1. Electrical Control Function
1.1 Abbreviation
T1: Indoor room temperature
T2: Evaporator coil temperature
T3: Condenser coil temperature
T4: Outdoor ambient temperature
T5: Compressor discharge temperature
Ts: Setting temperature
1.2 Main Protection
1.2.1 Compressor Restart Delay
1.2.2 Sensor protection at open circuit and
breaking disconnection.
1.2.3 Phase check function(for 3-phase models)
If the phase sequence is detected wrong or lack of
1 or 2 phase, the unit won’t start and there is error
code displayed on outdoor PCB.
1.2.4 Low pressure check function(for 48-60K
models)
The low pressure switch should be always closed. If
it is open, the system will stop until the fault is
cleared. Within 5 minutes after the compressor
starts and 4 minutes after defrosting ends, low
pressure switch won’t be checked.
Note: If this protection occurs 3 times within 20
minutes, it won’t recover automatically until the
main power is cut off.
1.2.5 Over-current protection(for 48-60K
models)
When compressor is running, if the current is over
twice of the rated for 3 seconds, the compressor will
stop and an error code will be displayed on the
outdoor PCB. If the current becomes normal, the
compressor will restart after 3 minutes.
1.3 Operation Modes and Functions
1.3.1 Fan mode
 Outdoor fan and compressor cease
operation.
 Temperature setting function is disabled, and
no preset temperature is displayed.

Indoor fan can be set to high, (
medium
), low,
or auto.
 Louver operates the same as in cooling
mode.
 Auto fan:
For floor standing units:
Auto fan will be controlled in line with cooling auto
fan with temperature set to be 24°C.
For other units:
High
Low
Medium
1.3.2 Cooling Mode
1.3.2.1 Compressor Running Guidelines
Once the compressor starts up, it will follow the
below rules:
When T1-Ts is higher than setting value, the
compressor and outdoor fan cease operation.
When T1-Ts is lower than setting value, the
compressor and outdoor fan activate..
T1-TS
On
Off
1.3.2.2 Outdoor Fan Running Guidelines
For single-fan units:
The outdoor fan will run following the compressor
For double-fan units:
The outdoor fans run depending on T3.