Heat pumps · Error codes · Ariston
923Ariston · NIMBUS NET R32 control platform (shared error list)
923 on an Ariston NIMBUS NET R32 control platform: Heating circuit pressure error
Short answer
On an Ariston heat pump, 923 means: Heating circuit pressure error. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Heating circuit pressure error.
Part involved: water pressure switch.
Likely causes:
- Water leakage in the hydraulic circuit.
- Faulty pressure switch.
- Defective cabling of the pressure switch.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
- Check the system pressure gauge: the user manual says 0.5-1.5 bar when cold; if low, ask the installer (repeated top-ups indicate a leak or expansion-vessel problem).
- Note the error code shown on the Sensys HD interface and contact the installer / Ariston service.
What the engineer will check
- Check for water leaks in the hydraulic circuit.
- Check pressure switch 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