S.101 on a Glow-worm GeniaAir: Heating mode: Compressor switched off The heat demand is met, the demand is ended by the system control and the heat deficit is offset. The compressor is switched off
Short answer
On a Glow-worm heat pump, S.101 means: Heating mode: Compressor switched off The heat demand is met, the demand is ended by the system control and the heat deficit is offset. The compressor is switched off. The heat pump keeps running.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Heating mode: Compressor switched off The heat demand is met, the demand is ended by the system control and the heat deficit is offset. The compressor is switched off.
Part involved: Heat pump control (status/Live Monitor).
When it shows: Heating mode: Compressor switched off The heat demand is met, the demand is ended by the system control and the heat deficit is offset. The compressor is switched off.
Likely causes:
- Operating status reported by the heat pump control (not a fault in itself).
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump keeps running.
Resetting itself: yes - status changes automatically with operating state.
Manual reset: not applicable.
What you can check
- Operating status only - no action needed. If heating or hot water is not being delivered for a long period, note the status code and tell your installer.
What the engineer will check
- None required unless heating/hot water is not delivered; then review status history, settings and application limits.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
Sources
- GeniaAir Appliance Interface installation and maintenance instructions ↗ · 8000043014_01 · page HPIM 7 8000043014_01 p.27 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026