581 on a NIBE heat pump: Warm outd air, cool. mode: Outdoor temperature at outdoor unit outside its working range
Short answer
On a NIBE heat pump, 581 means: Warm outd air, cool. mode: Outdoor temperature at outdoor unit outside its working range. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Warm outd air, cool. mode: Outdoor temperature at outdoor unit outside its working range.
Part involved: operating range / outdoor sensor.
When it shows: Outdoor temperature at outdoor unit outside its working range.
Likely causes:
- Outdoor temperature too high; defective sensor BT28.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - 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. Normally clears by itself when the outdoor temperature returns to the unit's operating range; check the outdoor unit is not buried in snow.
What the engineer will check
- Check outdoor ambient sensor BT28/Tho-A value and connection; confirm installation is within operating range. NIBE lists: Outdoor temperature too high; defective sensor BT28.
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 20 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026