Heat pumps · Error codes · Ariston
908Ariston · NIMBUS NET R32 control platform (shared error list)
908 on an Ariston NIMBUS NET R32 control platform: Expansion valve mismatch error
Short answer
On an Ariston heat pump, 908 means: Expansion valve mismatch error. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Expansion valve mismatch error.
Part involved: EXV configuration.
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.
Manual reset: Table column 'User reset' - can be reset from the interface (column interpretation from text extraction).
What you can check
- Note the error code shown on the Sensys HD interface and contact the installer / Ariston service.
- Check the consumer-unit breaker/isolator for the outdoor unit is on (do not reset repeatedly).
What the engineer will check
- Diagnose outdoor unit per Ariston service procedure (the installation manual gives description and reset type only).
Who to ask for: heat pump engineer.
Certification: Electrical competence.
What you might notice
Sources
- NIMBUS PLUS M NET R32 - Technical instructions for installation and maintenance (UK) - codes 3301719 3301720, doc 420000656201 EN ↗ · 420011311701 - 03/2024 · page 72 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026