Grundfos STP 2 fault 7A

What it means

Noisy pump due to vibration transmitted through the pump mounting surface.

Likely causes

1. Vibration through pump mounting surface
2. Low flow rates from cistern filling causing frequent pump cycling
3. Hot-water supply taken directly from top of hot-water cylinder
4. Entrapped air causing airlocks in supply pipe
5. Air not thoroughly purged from system
6. Leak in system
7. Drip in system
8. Air trapped in pump
9. Non-return valve incorrectly fitted in inlet pipe
10. Undersized tank causing insufficient supply
11. Incorrect outlet height causing hot-water-only delivery
12. Outlet positioned below mains inlet causing air ingress
13. Non-return valve fitted incorrectly in inlet pipe causing restricted flow or pump damage
14. Undersized pipework
15. Pipes routed under floor causing air traps
16. Other outlets fitted in inlet pipes
17. Shared (non-dedicated) hot/cold supplies
18. Blanked-off pipes
19. Restrictions in flexible hoses
20. Unsecured pipework
21. Direct mains connection causing pressure issues or pump damage
22. Jointing compounds/tape causing blockage or leaks
23. Shared supply pipe causing air ingress or reduced flow
24. Missing surrey flange causing air in hot water supply
25. Blocked strainers common on initial pump installation or new buildings due to jointing compounds, tapes, flux and debris flushed through system
26. Leak causing loss of tank air pressure
27. Leaks due to insufficient hose insertion depth
28. Debris ingress into pump causing blockage or damage if strainer omitted
29. Leaks due to under-tightened or incorrectly connected hoses
30. Mechanical strain on pump from misaligned pipework
31. Solder joint heat damaging plastic pump components
32. Air pockets from incorrectly routed pipework
33. Restricted or kinked flexible hoses
34. Additional outlet fittings on inlet pipework causing incorrect flow switch operation
35. Mechanical stress on pump from rigid pipe connection
36. Leaks from use of jointing compound instead of correct hose connections

Where to start

1. Check pump mounting surface
2. Switch off power supply for ten seconds
3. Switch power supply back on