5111 on a Worcester Bosch Bosch Compress 5800i AW: Alarm: signal from temperature sensor TC3 on the condenser outside permitted range
Short answer
On a Worcester Bosch heat pump, 5111 means: Alarm: signal from temperature sensor TC3 on the condenser outside permitted range. 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: Alarm: signal from temperature sensor TC3 on the condenser outside permitted range.
Part involved: TC3 condenser temperature sensor.
When it shows: Alarm: signal from temperature sensor TC3 on the condenser outside permitted range.
Likely causes:
- Printed test procedure refers to BUS cable wiring/defect.
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: 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
- Rectify wiring, power-cycle controller, repair/replace BUS cable.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
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