262 on a NIBE heat pump: Power transistor overheated (generated by heat pump): Overheated power transistor [other NIBE documents: IPM shows FO fault output signal 5 times in 60 minutes / Protection against damage if current too high]
Short answer
On a NIBE heat pump, 262 means: Power transistor overheated (generated by heat pump): Overheated power transistor [other NIBE documents: IPM shows FO fault output signal 5 times in 60 minutes / Protection against damage if current too high]. 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:
- Power transistor overheated (generated by heat pump): Overheated power transistor [other NIBE documents: IPM shows FO fault output signal 5 times in 60 minutes / Protection against damage if current too high].
- HW-start and HW-stop reset to factory settings: Hot water settings adjusted because of short operating time.
Part involved: inverter and compressor drive; heating medium flow, charge pump, particle filter.
When it shows: Overheated power transistor; IPM shows FO fault output signal 5 times in 60 minutes; Protection against damage if current too high; IPM displays FO fault output five times during 60 minutes Hot water settings adjusted because of short operating time.
Likely causes:
- S2060: Interference on incoming supply; service valve closed; insufficient refrigerant; compressor fault; defective inverter board QA40 (PWB2) | F2050: 15 V power supply to inverter PCB unstable | F2040: 15 V supply to inverter PCB unstable.
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.
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 heat pump and indoor unit breakers/RCD at the consumer unit are on; if one trips again, leave it off and call an engineer.
- 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.
What the engineer will check
- Check main and group fuses and cable connections, supply voltage under load, inverter terminal blocks, inverter mounting/cooling paste, compressor wiring and compressor. NIBE lists: 15 V supply to the inverter is unstable; Interference on incoming supply; service valve closed; insufficient refrigerant; compressor fault; defective inverter board QA40 (PWB2); 15 V power supply to inverter PCB unstable; 15 V supply to inverter PCB unstable.
- 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.
Who to ask for: NIBE-trained heat pump engineer and/or qualified electrician; NIBE-trained heat pump installer (NIBE PRO / VIP).
Certification: Electrical work to BS 7671 by a competent electrician (notifiable work under Part P in England & Wales); 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 6 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026