Grant Aerona R290 fault 4

What it means

Pump light-load protection has activated; pump will automatically re-start after 5 seconds.

Likely causes

1. Insufficient load on pump motor
2. Poor pump performance
3. Fuse is burnt out
4. Connection to PCB is loose or disconnects
5. Pump failure
6. Too low voltage
7. Pump rotors are stuck
8. Gas in the pump
9. Inlet pressure too low
10. Flow regulators or restrictors fitted in circuit
11. Valves not fully open causing flow restriction
12. External electrical isolator switched to OFF position
13. Heat pump switched OFF at the controller
14. No demand from heating system controls
15. Outdoor temperature too high to call heat pump on (weather regulated zones)
16. Active error code present on controller
17. Outside air temperature at or below 6°C
18. System water temperature at or below 6°C
19. Outdoor temperature too high for weather compensated zones to call heat pump
20. Active error code on controller display
21. Insufficient flow rate through primary circuit
22. PWM circulating pump not modulating correctly
23. Blockage or air in primary circuit
24. Pump fault or blockage causing low flow
25. External electrical isolator switched OFF for extended period during cold weather

Where to start

1. Check system flow and pressure
2. Check for air in system
3. Check inlet water pressure