Heat pumps · Error codes · Ariston
918Ariston · NIMBUS NET R32 control platform (shared error list)
918 on an Ariston NIMBUS NET R32 control platform: Pump down error
Short answer
On an Ariston heat pump, 918 means: Pump down 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: Pump down error.
Part involved: pump-down function.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: Table column 'HP power OFF / Service reset' - requires power-off/service reset (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 outdoor unit is not blocked by leaves, debris or snow.
- 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).
- Refrigerant-circuit work requires F-gas certified engineer.
Who to ask for: heat pump / refrigeration engineer.
Certification: F-gas category I (refrigerant circuit).
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