3091 on a Worcester Bosch Bosch Compress 5800i AW: Room temperature sensor defective
Short answer
On a Worcester Bosch heat pump, 3091 means: Room temperature sensor defective. 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: Room temperature sensor defective.
Part involved: room temperature sensor.
When it shows: Room temperature sensor defective.
Likely causes:
- Defective room sensor/remote control.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Clears when cause removed.
Manual reset: Reset/acknowledge via UI 800 fault menu after cause removed.
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
What the engineer will check
- Switch frost protection to outside-temperature-controlled if needed; replace remote control.
Who to ask for: heat pump installer / controls engineer.
Certification: None specific; electrical isolation required before wiring checks.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Controller / thermostat problem on the Bosch Compress 5800i AW (R290 monobloc): 1 report
Sources
- Installationsanleitung Bedienfeld UI 800 (Luft-Wasser-Wärmepumpe) 6721833375 ↗ · 6721833375 (2023/09) DE, AT, CH, LU · page 21 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026