151 on a NIBE heat pump: Sen flt: CL11-BT51 pool temp sensor: Sensor input unreasonable value for longer than 5 s
Short answer
On a NIBE heat pump, 151 means: Sen flt: CL11-BT51 pool temp sensor: Sensor input unreasonable value for longer than 5 s. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 2 sources
What it means
The manuals for this range word it in different ways:
- Sen flt: CL11-BT51 pool temp sensor: Sensor input unreasonable value for longer than 5 s.
- Sens flt from heat pump (BP8/BP4): Repeated sensor failures, low-pressure sensor BP8 (PSL) / high-pressure sensor BP4 (PSH) [other NIBE documents: Sensor fault, low pressure transmitter in F2050 / Alarm generated by the heat pump: low pressure sensor fault].
Part involved: temperature/pressure sensor.
When it shows: Sensor input unreasonable value for longer than 5 s Repeated sensor failures, low-pressure sensor BP8 (PSL) / high-pressure sensor BP4 (PSH); Sensor fault, low pressure transmitter in F2050; Alarm generated by the heat pump: low pressure sensor fault.
Likely causes:
- Sensor not connected; open-circuit or defective sensor.
- S2060: Open/short circuit on sensor input; defective baseboard AA2; fault in refrigerant circuit | F2050: Open/short circuit on sensor input; defective control board PWB1; fault in refrigerant circuit.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - Pool pump stops.
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.
What the engineer will check
- Check sensor and its connections/wiring against the wiring diagram; measure sensor resistance against the NIBE temperature/resistance table; check the relevant PCB input. NIBE lists: Sensor not connected; open-circuit or defective sensor.
- Check sensor and its connections/wiring against the wiring diagram; measure sensor resistance against the NIBE temperature/resistance table; check the relevant PCB input. NIBE lists: Open/short circuit on sensor input; defective baseboard AA2; fault in refrigerant circuit; Open/short circuit on sensor input; defective control board PWB1; fault in refrigerant circuit.
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
- TECHNICAL INFORMATION - ALARM LIST SMO 40 (TIF EN 2042-1, M12658EN) ↗ · TIF EN 2042-1 M12658EN · page 14 · Reviewed 23 September 2026
- Installer manual Air/water heat pump NIBE S2060 UK 1x230V IHB EN 2623-3 (831281) ↗ · IHB EN 2623-3 · page 31 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026