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. Hot-water supply taken directly from top of hot-water cylinder
3. Entrapped air causing airlocks in supply pipe
4. Air not thoroughly purged from system
5. Leak in system
6. Drip in system
7. Air trapped in pump
8. Non-return valve incorrectly fitted in inlet pipe
9. Blocked strainers common on initial pump installation or new buildings due to jointing compounds, tapes, flux and debris flushed through system
10. Leak causing loss of tank air pressure
11. Low flow rates from cistern filling causing frequent pump cycling
12. Undersized pipework
13. Pipes routed under floor causing air traps
14. Other outlets fitted in inlet pipes
15. Shared (non-dedicated) hot/cold supplies
16. Blanked-off pipes
17. Restrictions in flexible hoses
18. Unsecured pipework
19. Debris ingress into pump causing blockage or damage if strainer omitted

Where to start

1. Check pump mounting surface
2. Check hot-water supply connection point on cylinder
3. Inspect for airlocks in supply pipe