299 on a NIBE heat pump: Wrong version PCA Base: Firmware on base card (AA2) too low for inverter communication [other NIBE documents: Base board AA2 software too low for inverter communication]
Short answer
On a NIBE heat pump, 299 means: Wrong version PCA Base: Firmware on base card (AA2) too low for inverter communication [other NIBE documents: Base board AA2 software too low for inverter communication]. 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 manuals for this range word it in different ways:
- Wrong version PCA Base: Firmware on base card (AA2) too low for inverter communication [other NIBE documents: Base board AA2 software too low for inverter communication].
- Uncertain sensor accuracy: Delta BT3-BT12 greater than 2 K after calibration.
Part involved: PCB / software configuration; temperature/pressure sensor.
When it shows: Firmware on base card (AA2) too low for inverter communication; Base board AA2 software too low for inverter communication Delta BT3-BT12 greater than 2 K after calibration.
Likely causes:
- Base board AA2 needs replacing.
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 blocked; reset when correct version detected; 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.
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: Base board AA2 needs replacing.
- Check sensor and its connections/wiring against the wiring diagram; measure sensor resistance against the NIBE temperature/resistance table; check the relevant PCB input.
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; Electrical work to BS 7671 by a competent person.
What you might notice
Sources
- ALARM LIST - NIBE products with Emmy display, Version 1747-1 (updated 2017-11-23) ↗ · 1747-1 · page 9 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026