294 on a NIBE heat pump: Not compatible heat pump: Outdoor unit connected is not compatible (e.g. VVM 320 with other than F2030-7/-9, F2040-8/-12) or DIP switches wrongly set [other NIBE documents: The outdoor air heat pump is not compatible / Heat pump and indoor module are incompatible]
Short answer
On a NIBE heat pump, 294 means: Not compatible heat pump: Outdoor unit connected is not compatible (e.g. VVM 320 with other than F2030-7/-9, F2040-8/-12) or DIP switches wrongly set [other NIBE documents: The outdoor air heat pump is not compatible / Heat pump and indoor module are incompatible]. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manuals for this range word it in different ways:
- Not compatible heat pump: Outdoor unit connected is not compatible (e.g. VVM 320 with other than F2030-7/-9, F2040-8/-12) or DIP switches wrongly set [other NIBE documents: The outdoor air heat pump is not compatible / Heat pump and indoor module are incompatible].
- Recurring low pressure: 5 repeated low pressure alarms within 4 hours.
Part involved: PCB / software configuration; pressure switches/sensors, expansion valve.
When it shows: Outdoor unit connected is not compatible (e.g. VVM 320 with other than F2030-7/-9, F2040-8/-12) or DIP switches wrongly set; The outdoor air heat pump is not compatible; Heat pump and indoor module are incompatible; Heat pump and indoor module do not function together due to technical parameters; Heat pump and indoor module do not work properly together due to technical parameters 5 repeated low pressure alarms within 4 hours.
Likely causes:
- S2060: Heat pump and indoor module not compatible | F2050: Outdoor module and indoor module are not compatible | F2040: Outdoor module and indoor module are not compatible.
- S2125: Lack of refrigerant; blocked expansion valve; disruption in refrigerant circuit | F2120: Lack of refrigerant; blocked expansion valve; disruption in refrigerant circuit.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no/unknown - Compressor/hot water blocked; 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. Note the alarm and contact your installer; no homeowner action beyond resetting.
- 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. Air source systems: check the outdoor unit is clear of leaves/snow/ice. Read the heating system pressure gauge and note the reading for your installer.
What the engineer will check
- Check serial number/software versions, PCB type and DIP switch settings; update software or replace PCB as required. NIBE lists: Upgrade of outdoor unit failed; no software in outdoor unit; Heat pump and indoor module not compatible; Outdoor module and indoor module are not compatible.
- Check heating medium flow, particle filter and circulation pump; check pressure switches/sensors, expansion valve, service valves and refrigerant charge (F-gas qualified). NIBE lists: Lack of refrigerant; blocked expansion valve; disruption in refrigerant circuit.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP); Heat pump engineer with F-gas qualification (NIBE-trained / NIBE PRO installer).
Certification: None specific beyond competent heat pump installer; electrical work to BS 7671; F-gas certification for refrigerant circuit work (plus flammable-refrigerant competence for R290/R32 models).
What you might notice
Sources
- TECHNICAL INFORMATION - ALARM LIST SMO 40 (TIF EN 2042-1, M12658EN) ↗ · TIF EN 2042-1 M12658EN · page 8 · Reviewed 23 September 2026
- 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