233 on a NIBE heat pump: Fan alarm in outd air heat pump: 5 unsuccessful start attempts [other NIBE documents: No feedback signal from the fan 5 times within 240 minutes / Deviations in the fan speed in F2050]
Short answer
On a NIBE heat pump, 233 means: Fan alarm in outd air heat pump: 5 unsuccessful start attempts [other NIBE documents: No feedback signal from the fan 5 times within 240 minutes / Deviations in the fan speed in F2050]. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Fan alarm in outd air heat pump: 5 unsuccessful start attempts [other NIBE documents: No feedback signal from the fan 5 times within 240 minutes / Deviations in the fan speed in F2050].
Part involved: fan motor.
When it shows: 5 unsuccessful start attempts; No feedback signal from the fan 5 times within 240 minutes; Deviations in the fan speed in F2050; Heat pump (selected outdoor unit) sends fault message to controller.
Likely causes:
- S2125: Fan blocked or not connected; significant wind effect | F2120: Fan blocked or not connected; significant wind effect | S2060: Fan blocked or not connected; defective or dirty baseboard AA2; defective fan motor; tripped fuse F2 | F2050: Fan cannot rotate freely; defective PWB1; defective fan motor; PWB1 dirty; fuse F2 tripped.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no/unknown - Compressor blocked.
Manual reset: Reset from the controller alarm menu ('reset alarm' / 'Reset alarm and try again'); alarm recurs if the cause remains.
What you can check
- Read the alarm text and the 'info/action' help on the controller display (VVM/SMO or S-series smartguide). NIBE's manuals let the homeowner select 'reset alarm' ('Reset alarm and try again' on S-series); if the lamp returns to normal the alarm has cleared. If it comes back, do not keep resetting: select 'aid mode' ('Auxiliary operation' on S-series) if offered, so any electric additional heat keeps heat/hot water going, and contact your installer. Check the outdoor unit is not blocked by leaves, snow, ice or stored items and air can flow freely.
What the engineer will check
- Check fan rotates freely, fan motor, fan connections, fuse and control board in the outdoor unit. NIBE lists: Fan blocked or not connected; significant wind effect; Fan blocked or not connected; defective or dirty baseboard AA2; defective fan motor; tripped fuse F2; Fan cannot rotate freely; defective PWB1; defective fan motor; PWB1 dirty; fuse F2 tripped.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent person.
What you might notice
Sources
- Installer manual Air/water heat pump NIBE S2125 UK 1x230V IHB EN 2525-1 (831874) ↗ · IHB EN 2525-1 · page 41 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026