711 on an alpha innotec heat pump: External temp. sensor. Please call installer: Break or short circuit in the outdoor (external) temperature sensor. No fault shutdown; value fixed to -5 °C
Short answer
On an alpha innotec heat pump, 711 means: External temp. sensor. Please call installer: Break or short circuit in the outdoor (external) temperature sensor. No fault shutdown; value fixed to -5 °C. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: External temp. sensor. Please call installer: Break or short circuit in the outdoor (external) temperature sensor. No fault shutdown; value fixed to -5 °C.
When it shows: Break or short circuit in the outdoor (external) temperature sensor. No fault shutdown; value fixed to -5 °C.
Likely causes:
- Outdoor sensor defective.
- Plug/cable fault.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: no.
Manual reset: none - no fault shutdown.
What you can check
- Note the error number and text shown on the Luxtronik display.
- Acknowledge the message by pressing the rotary pushbutton for about 7 seconds (as the Luxtronik manual permits); if the same error reappears, contact your installer or ait customer service with the error number.
- Check the heat pump breakers/isolator at the consumer unit are on (do not open any casing).
What the engineer will check
- Check external temperature sensor, plug and connection line.
Who to ask for: heat pump service engineer (electrical/controls).
What you might notice
Sources
- Operating manual Luxtronik heating and heat pump control Part 2 (UK) 83055400lUK - 2.1 ↗ · 83055400lUK 2.1 · page 52 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026