Heat pumps · Error codes · Ariston
731Ariston · NIMBUS NET R32 control platform (shared error list)
731 on an Ariston NIMBUS NET R32 control platform: Buffer overtemperature - buffer filling inhibited
Short answer
On an Ariston heat pump, 731 means: Buffer overtemperature - buffer filling inhibited. 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 manual says: Buffer overtemperature - buffer filling inhibited.
Part involved: buffer tank.
Likely causes:
- Buffer sensor not connected or damaged.
- Hydraulic diagram setting.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
What you can check
- Note the error code shown on the Sensys HD interface and contact the installer / Ariston service.
What the engineer will check
- Check the hydraulic diagram.
- Check the buffer sensor connection and replace if necessary.
Who to ask for: heat pump controls / hydronics.
Certification: Competent heating engineer; electrical competence for wiring checks.
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 71 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026