273 on a NIBE heat pump: HW-start and HW-stop reset to factory settings: Hot water settings adjusted because of short operating times [other NIBE documents: Set hot water levels cannot be reached]
Short answer
On a NIBE heat pump, 273 means: HW-start and HW-stop reset to factory settings: Hot water settings adjusted because of short operating times [other NIBE documents: Set hot water levels cannot be reached]. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manuals for this range word it in different ways:
- HW-start and HW-stop reset to factory settings: Hot water settings adjusted because of short operating times [other NIBE documents: Set hot water levels cannot be reached].
- Com. error slave 3: Temporarily no communication with slave heat pump (EB103).
Part involved: heating medium flow, charge pump, particle filter; PCB / accessory board communication.
When it shows: Hot water settings adjusted because of short operating times; Set hot water levels cannot be reached Temporarily no communication with slave heat pump (EB103).
Likely causes:
- Incorrectly set values.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Information only |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - HW start/stop for economy and normal reset to factory settings; HW-start/HW-stop for economy and normal set to factory default.
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. Read the heating system pressure gauge and check that radiator/underfloor thermostats are not all closed; check heating and hot water temperature settings have not been changed.
- 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 heating medium flow (pump speed/settings, particle filter, air in system), heating curve and hot water settings, correct sensor placement and flow/return connections. NIBE lists: Incorrectly set values.
- 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.
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
- TECHNICAL INFORMATION - ALARM LIST SMO 40 (TIF EN 2042-1, M12658EN) ↗ · TIF EN 2042-1 M12658EN · page 17 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026