495 on a NIBE heat pump: Sensor BT14 or BP9 loose or defective: Sensor BT14 or BP9 has come loose or is otherwise defective
Short answer
On a NIBE heat pump, 495 means: Sensor BT14 or BP9 loose or defective: Sensor BT14 or BP9 has come loose or is otherwise defective. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Sensor BT14 or BP9 loose or defective: Sensor BT14 or BP9 has come loose or is otherwise defective.
Part involved: temperature/pressure sensor.
When it shows: Sensor BT14 or BP9 has come loose or is otherwise defective.
Likely causes:
- S2125: Discharge sensor BT14 or high pressure sensor BP9 has come loose and gives incorrect values.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: no/unknown - not stated.
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: Discharge sensor BT14 or high pressure sensor BP9 has come loose and gives incorrect values.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent person.
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