Heat pumps · Error codes · alpha innotec
759alpha innotec · alpha innotec, all models
759 on an alpha innotec heat pump: TDI message: Thermal disinfection could not be carried out correctly 5 times in succession
Short answer
On an alpha innotec heat pump, 759 means: TDI message: Thermal disinfection could not be carried out correctly 5 times in succession. 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: TDI message: Thermal disinfection could not be carried out correctly 5 times in succession.
When it shows: Thermal disinfection could not be carried out correctly 5 times in succession.
Likely causes:
- Additional heat generator setting.
- Safety temperature limiter.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: unknown.
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 setting of additional heating generator and safety temperature limiter.
Who to ask for: heat pump / heating engineer.
What you might notice
Sources
- Operating manual Luxtronik heating and heat pump control Part 2 (UK) 83055400lUK - 2.1 ↗ · 83055400lUK 2.1 · page 53 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026