Daikin Altherma fault H8-00

What it means

DC voltage or current sensor abnormality based on the compressor running frequency and the input current.

Likely causes

1. Faulty main PCB
2. Faulty inverter PCB
3. Faulty compressor or miswiring of the compressor power supply cable
4. Faulty reactor
5. Faulty refrigerant pressure sensor
6. Poor water flow through high pressure side plate heat exchanger
7. Incorrect refrigerant charge
8. Bad contact between refrigerant loop and inverter heat sink
9. Lack of refrigerant
10. Faulty expansion valve
11. Faulty suction thermistor
12. Blockages in refrigerant circuit
13. Faulty discharge pipe thermistor
14. Worn or damaged compressor dampers causing vibration/noise
15. Compressor guard timer active
16. Normal inverter control behavior when target temperature achieved
17. Water pump software control behaviour based on setting [F-0D]
18. Special software control activated - water loop temperature is too low causing ONLY the backup heater to operate
19. Faulty compressor winding
20. High pressure switch confirmed faulty during checking procedure
21. Flammable refrigerant remaining dissolved in compressor lubricant
22. Wrong assembly during repair
23. Excessive heat applied during brazing near compressor pipes

Where to start

1. Perform a check of the main PCB
2. Perform a check of the inverter PCB
3. Perform a check of the compressor