254 on a NIBE heat pump: Communication error: Communication fault with accessory board
Short answer
On a NIBE heat pump, 254 means: Communication error: Communication fault with accessory board. The manual does not say whether the heat pump stops. 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:
- Communication error: Communication fault with accessory board.
- Communication fault to inverter: Alarm 203 from heat pump for 20 seconds [other NIBE documents: Alarm 203 from the air/water heat pump for 20 seconds / Communication between inverter circuit board and baseboard interrupted].
Part involved: PCB / accessory board communication.
When it shows: Communication fault with accessory board Alarm 203 from heat pump for 20 seconds; Alarm 203 from the air/water heat pump for 20 seconds; Communication between inverter circuit board and baseboard interrupted; Communication between inverter board and control board broken; Communication between inverter circuit board and control board interrupted.
Likely causes:
- F2050: F2050 not powered; fault in the communication cable | F2040: F2040 not powered; fault in the communication cable.
- S2125: Poor connection between PCB and inverter; inverter unpowered or broken | F2120: Poor connection between PCB and inverter; inverter unpowered or broken | S2060: Poor connection between PCB and inverter; inverter unpowered or broken; defective baseboard AA2 | F2050: Open circuit in connection between boards; defective inverter board; defective PWB1.
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 - not stated.
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. Check the breakers for the heat pump, indoor module and any accessories are on at the consumer unit.
What the engineer will check
- Check communication cables and connectors between PCBs/accessory boards, DIP-switch addressing, power supply to the accessory board, and that accessories activated in the menu are actually fitted. NIBE lists: F2050 not powered; fault in the communication cable; F2040 not powered; fault in the communication cable.
- Check communication cables and connectors between PCBs/accessory boards, DIP-switch addressing, power supply to the accessory board, and that accessories activated in the menu are actually fitted. NIBE lists: Poor connection between PCB and inverter; inverter unpowered or broken; Poor connection between PCB and inverter; inverter unpowered or broken; defective baseboard AA2; Open circuit in connection between boards; defective inverter board; defective PWB1.
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent person.
What you might notice
Sources
- Installer manual Air/water heat pump NIBE F2050 UK 1x230V IHB EN 2426-2 (731658) ↗ · IHB EN 2426-2 · page 45 · 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