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Testing the LEV

DEP | MITSUBISHI ELECTRIC EUROPE | UK

Created on May 11, 2021

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Transcript

Testing the LEV

Poor Performance

If your indoor unit is not performing well in heating or cooling, the LEV may not be operating correctly

If the LEV is jammed open the evaporator coil will flood with liquid during cooling mode

Title 2

If the LEV is stuck closed you will get no refrigerant flow through the indoor coil in heating or cooling

You can try performing a LEV reset to set the valve head back to the factory position

If the LEV reset works it would be good practise to change the LEV head anyway as it may stick again

LEV Reset Procedure

Indoor unit reset

  • Turn mains power supply off to the indoor fan coil
  • Disconnect M-net plug from PCB (CN2M)
  • Power the unit back on for at least 90 seconds
  • Power off again and reconnect CN2M
  • Power back on and the valve will be reset to factory position

Full system reset

  • Turn the mains power supply off to the full system
  • Disconnect the M-net connection (TB3) at the outdoor unit
  • Power back on the Indoor units and BC box
  • After 90 seconds power down again
  • Reconnect the M-net at TB3 on the outdoor unit
  • Power the system back on in the order of Indoors, Outdoor, then BC box

LEV Check - Heating

If the LEV valve is stuck closed there will be no heating flow through the indoor coil If the LEV valve is stuck open you will still get full heating performance

When you suspect the valve is stuck closed, put the indoor unit into heating mode and feel the gas pipe entering the coil to see if it gets warm for the first 60 seconds

The heat will quickly disperse as there is no heat flow through the coil and LEV You can try a LEV reset as a temporary fix but the LEV head will need replacing

Heating Flow

Heating Flow

LEV

LEV Check - Cooling

If the LEV valve is stuck closed there will be no cooling through the indoor coil If the LEV valve is stuck open the coil will flood with liquid refrigerant

When one indoor fan coils LEV is stuck open, this faulty unit will flood with liquid and still cool but it will deprive the other fan coils of their share of refrigerant

Use the SW4 dip switches on the outdoor unit to monitor the TH2 and TH3 indoor coil sensor readings to determine if the correct indoor superheat is being achieved

Carry out a LEV reset on the flooded evaporator and run in fan only mode for a while to boil off all of the liquid refrigerant from the coil, then replace the LEV head

Cooling Flow

Cooling Flow

LEV