806 on an alpha innotec heat pump: ModBus SEC: SEC board has no ModBus communication for at least 10 s or query failed 10 times in a row. Reset autom
Short answer
On an alpha innotec heat pump, 806 means: ModBus SEC: SEC board has no ModBus communication for at least 10 s or query failed 10 times in a row. Reset autom. 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: ModBus SEC: SEC board has no ModBus communication for at least 10 s or query failed 10 times in a row. Reset autom.
When it shows: SEC board has no ModBus communication for at least 10 s or query failed 10 times in a row. Reset autom.
Likely causes:
- SEC board Modbus wiring.
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: yes.
Manual reset: automatic.
What you can check
- Note the error number and text shown on the Luxtronik display.
- The controller resets this automatically after the stated time - wait for the automatic restart before calling.
- 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 ModBus - SEC board wiring.
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 55 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026