Heat pumps · Error codes · iDM Energiesysteme
091iDM Energiesysteme · TERRA SW (2013)
091 on an iDM Energiesysteme TERRA SW: Central unit 2 not online: Communication problem - slave board A7 not found
Short answer
On an iDM Energiesysteme heat pump, 091 means: Central unit 2 not online: Communication problem - slave board A7 not found. 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: Central unit 2 not online: Communication problem - slave board A7 not found.
Part involved: Central unit 2 not online.
When it shows: Communication problem - slave board A7 not found.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
What you can check
- Note the fault number and text shown after tapping the fault symbol on the Navigator display. 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.71 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026