Daikin Altherma fault L5-00

What it means

An output overcurrent is detected by checking the current that flows in the inverter DC section, causing the unit to stop operating.

Likely causes

1. Closed stop valve in the refrigerant circuit
2. Clogged refrigerant circuit
3. Refrigerant overcharge or shortage
4. Non-condensables and/or humidity in the refrigerant circuit
5. Faulty inverter PCB
6. Faulty compressor or miswiring of the compressor power supply cable
7. Faulty or disturbance of the power supply (power supply MUST be within range of nominal operating voltage ±4%)
8. Power drop
9. Short circuit
10. Thermal interface grease NOT applied properly on the heat sink
11. Faulty refrigerant pressure sensor
12. Poor water flow through high pressure side plate heat exchanger
13. Incorrect refrigerant charge
14. Bad contact between refrigerant loop and inverter heat sink
15. Lack of refrigerant
16. Faulty expansion valve
17. Faulty suction thermistor
18. Blockages in refrigerant circuit
19. Faulty discharge pipe thermistor
20. Worn or damaged compressor dampers causing vibration/noise
21. Compressor guard timer active
22. Normal inverter control behavior when target temperature achieved
23. Water pump software control behaviour based on setting [F-0D]
24. Special software control activated - water loop temperature is too low causing ONLY the backup heater to operate
25. Faulty compressor winding
26. High pressure switch confirmed faulty during checking procedure
27. Flammable refrigerant remaining dissolved in compressor lubricant
28. Wrong assembly during repair
29. Excessive heat applied during brazing near compressor pipes

Where to start

1. Check that all stop valves of the refrigerant circuit are open
2. Check if the refrigerant circuit is clogged
3. Check if the refrigerant circuit is correctly charged