Grant Aerona R290 fault P21
Abnormal operation of DC pump
Heat pumpWhat it means
Abnormal DC pump operation due to pump fault, water shortage/blockage, faulty connections, or faulty hydraulic PCB.
Likely causes
- Faulty connection between water pump and hydraulic PCB
- The hydraulic PCB is faulty
Where to start
- Check connections between water pump and hydraulic PCB
- Check the hydraulic PCB
- Confirm mains power supply is isolated before starting
The full answer, free
- 1 more check in order
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 59), right under the answer
Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.
From the Grant manual for the Aerona R290. Check the model on the data plate before you order parts.
Other Grant Aerona R290 fault codes
- 1Pump over-voltage protection
- 2Pump under-voltage protection
- 3Pump over-current protection
- 4Pump light-load protection
- 5Pump phase loss protection
- 6Pump block protection
- 7Pump over-temperature protection
- E01Connection fault between wiring centre and heat pump
- E10Communication failure between hydraulic PCB and refrigerant PCB
- E13Discharge pressure sensor fault
- E15DC bus voltage is too low
- E16DC bus voltage is too high
- E17AC current protection (input current)
- E18IPM module is abnormal
- E19PFC abnormal
- E20Compressor failed to start
- E21Compressor phase loss
- E22Inverter module reset
- E23Compressor over-current
- E24PFC module temperature is too high
- E25Current detection circuit failure
- E26Out of step
- E27PFC module temperature sensor is abnormal
- E29IPM module temperature is too high