028 on an iDM Energiesysteme TERRA SW: Soft starter 1 (see LED): Soft-starter fault (< 5 times in 24 h). The type of fault is indicated on the soft starter
Short answer
On an iDM Energiesysteme heat pump, 028 means: Soft starter 1 (see LED): Soft-starter fault (< 5 times in 24 h). The type of fault is indicated on the soft starter. 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: Soft starter 1 (see LED): Soft-starter fault (< 5 times in 24 h). The type of fault is indicated on the soft starter.
Part involved: Soft starter 1 (see LED).
When it shows: Soft-starter fault (< 5 times in 24 h). The type of fault is indicated on the soft starter.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Counts towards 24 h lockout thresholds.
What you can check
- Note the fault number and text shown after tapping the fault symbol on the Navigator display. Check the heat pump's breaker/isolator at the consumer unit is on and has not tripped. 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.
Certification: Qualified electrician / heat pump engineer (electrical fault-finding).
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