56 on a NIBE heat pump: Incorrect serial number: Serial number does not exist [other NIBE documents: The heat pump has a serial number that does not exist / The heat pump has an incorrect serial number]
Short answer
On a NIBE heat pump, 56 means: Incorrect serial number: Serial number does not exist [other NIBE documents: The heat pump has a serial number that does not exist / The heat pump has an incorrect serial number]. 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: Incorrect serial number: Serial number does not exist [other NIBE documents: The heat pump has a serial number that does not exist / The heat pump has an incorrect serial number].
Part involved: PCB / software configuration.
When it shows: Serial number does not exist; The heat pump has a serial number that does not exist; The heat pump has an incorrect serial number.
Likely causes:
- F2120: Incorrect software in outdoor unit or incompatible outdoor unit.
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 stopped and relays deactivated; Compressors stopped and relay deactivated.
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.
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: Incorrectly entered serial number; Incorrect software in outdoor unit or incompatible outdoor unit.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: 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 3 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026