035 on an iDM Energiesysteme TERRA SW: Minimum heat storage temperature undershot: Heat storage (buffer) temperature required for defrosting was undershot
Short answer
On an iDM Energiesysteme heat pump, 035 means: Minimum heat storage temperature undershot: Heat storage (buffer) temperature required for defrosting was undershot. 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: Minimum heat storage temperature undershot: Heat storage (buffer) temperature required for defrosting was undershot.
Part involved: Minimum heat storage temperature undershot.
When it shows: Heat storage (buffer) temperature required for defrosting was undershot.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
What you can check
- Note the fault number and text shown after tapping the fault symbol on the Navigator display. Check the outdoor unit is not blocked by snow, ice, leaves or debris and that airflow around it is clear. If the fault recurs several times, contact iDM customer service/your installer.
What the engineer will check
- Diagnose per iDM service documentation for the unit (not obtained): check the monitored circuit/component named in the fault.
Who to ask for: heat pump engineer.
What you might notice
Sources
- IDM Wärmepumpen mit Navigatorregelung 2.0 - Bedienungsanleitung (812152 Rev.3) ↗ · 812152 Rev.3 · page p.70 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026