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. Compressor guard timer active
9. Special software control activated - water loop temperature is too low causing ONLY the backup heater to operate
10. Faulty compressor winding
11. Faulty expansion valve
12. Faulty suction thermistor
13. Blockages in refrigerant circuit
14. Faulty discharge pipe thermistor
15. Worn or damaged compressor dampers causing vibration/noise
16. Normal inverter control behavior when target temperature achieved
17. Flammable refrigerant remaining dissolved in compressor lubricant
18. Wrong assembly during repair
19. 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