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Heat pumps · Error codes · NIBE
354NIBE · NIBE, all models

354 on a NIBE heat pump: Slave EB101 / failed sensor calibration BT3-BT12: Delta BT3-BT12 larger than 2 K after calibration [other NIBE documents: Delta BT3-BT12 greater than 2 K after calibration]

Short answer

On a NIBE heat pump, 354 means: Slave EB101 / failed sensor calibration BT3-BT12: Delta BT3-BT12 larger than 2 K after calibration [other NIBE documents: Delta BT3-BT12 greater than 2 K after calibration]. 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:

  • Slave EB101 / failed sensor calibration BT3-BT12: Delta BT3-BT12 larger than 2 K after calibration [other NIBE documents: Delta BT3-BT12 greater than 2 K after calibration].
  • Compressor speed too low: Compressor speed below lowest permitted speed.

Part involved: temperature/pressure sensor; inverter and compressor drive.

When it shows: Delta BT3-BT12 larger than 2 K after calibration; Delta BT3-BT12 greater than 2 K after calibration Compressor speed below lowest permitted speed.

Likely causes:

  • Flow-related.
  • S2125: Inverter safety function reduces speed outside compressor working range | F2120: Inverter safety function reduces speed outside compressor working range.

Is it safe?

Does the heat pump stop?Not stated
SeverityFault — 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 - Circulation pump changes from auto to manual speed; Changes from auto to manual pump speed.

Manual reset: Reset from the controller alarm menu ('reset alarm' / 'Reset alarm and try again'); alarm recurs if the cause remains - NIBE: Circulation pump changes from auto to manual speed; Changes from auto to manual pump speed.

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 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.

What the engineer will check

  • Check sensor and its connections/wiring against the wiring diagram; measure sensor resistance against the NIBE temperature/resistance table; check the relevant PCB input. NIBE lists: Flow-related.
  • 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: Inverter safety function reduces speed outside compressor working range.

Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP); NIBE-trained heat pump engineer and/or qualified electrician.

Certification: Electrical work to BS 7671 by a competent person; Electrical work to BS 7671 by a competent electrician (notifiable work under Part P in England & Wales).

What you might notice

Sources

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026