292 on a NIBE heat pump: Sen flt: BT74 cool/heat sen.: Sensor BT74 on AUX input not connected/defective
Short answer
On a NIBE heat pump, 292 means: Sen flt: BT74 cool/heat sen.: Sensor BT74 on AUX input not connected/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 manuals for this range word it in different ways:
- Sen flt: BT74 cool/heat sen.: Sensor BT74 on AUX input not connected/defective.
- Low temperature water: Low temperature during cooling mode.
Part involved: temperature/pressure sensor; heating medium flow, charge pump, particle filter.
When it shows: Sensor BT74 on AUX input not connected/defective Low temperature during cooling mode.
Likely causes:
- Open circuit or short circuit on sensor input; defective sensor.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: no/unknown - According to selected measure in menu.
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.
- 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. Read the heating system pressure gauge and check that radiator/underfloor thermostats are not all closed; check heating and hot water temperature settings have not been changed.
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: Open circuit or short circuit on sensor input; defective sensor.
- Check heating medium flow (pump speed/settings, particle filter, air in system), heating curve and hot water settings, correct sensor placement and flow/return connections.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent person; None specific beyond competent heat pump installer; electrical work to BS 7671.
What you might notice
Sources
- TECHNICAL INFORMATION - ALARM LIST SMO 40 (TIF EN 2042-1, M12658EN) ↗ · TIF EN 2042-1 M12658EN · page 7 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026