34 on a NIBE heat pump: Sensor fault EP30-BT54: Sensor not connected/defective (solar tank/coil) [other NIBE documents: Solar coil sensor not connected/defective]
Short answer
On a NIBE heat pump, 34 means: Sensor fault EP30-BT54: Sensor not connected/defective (solar tank/coil) [other NIBE documents: Solar coil sensor not connected/defective]. 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: Sensor fault EP30-BT54: Sensor not connected/defective (solar tank/coil) [other NIBE documents: Solar coil sensor not connected/defective].
Part involved: temperature/pressure sensor.
When it shows: Sensor not connected/defective (solar tank/coil); Solar coil sensor not connected/defective.
Likely causes:
- Open circuit or short circuit on sensor input; defective sensor.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no/unknown - Solar addition blocked; Switches off solar function.
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: Open circuit or short circuit on sensor input; defective sensor.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent person.
Sources
- TECHNICAL INFORMATION - ALARM LIST SMO 40 (TIF EN 2042-1, M12658EN) ↗ · TIF EN 2042-1 M12658EN · page 3 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026