additional-heat-is-now-working-at-its-highest-temperature on an IVT Greenline HE: The electric additional heat begins to be stepped down. The warning is activated in additional heat mode if the sensor T8 approaches the highest temperature permitted for T8. The warning is blocked during hot water peaks or extra hot water
Short answer
On an IVT heat pump, additional-heat-is-now-working-at-its-highest-temperature means: The electric additional heat begins to be stepped down. The warning is activated in additional heat mode if the sensor T8 approaches the highest temperature permitted for T8. The warning is blocked during hot water peaks or extra hot water. 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: The electric additional heat begins to be stepped down. The warning is activated in additional heat mode if the sensor T8 approaches the highest temperature permitted for T8. The warning is blocked during hot water peaks or extra hot water.
When it shows: The electric additional heat begins to be stepped down. The warning is activated in additional heat mode if the sensor T8 approaches the highest temperature permitted for T8. The warning is blocked during hot water peaks or extra hot water.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Yes - The warning is deactivated when the sensor temperature falls sufficiently.
What you can check
- Note the full alarm text including the component designation (e.g. E21.T6) - IVT asks for it when you contact the dealer.
What the engineer will check
- Investigate per the installer guide alarm description and operating data.
Who to ask for: heat pump engineer.
What you might notice
Sources
- Installer Guide Greenline HE C6-C11 E6-E11 1x230V (6 720 802 419 (2012/06) en) ↗ · 6 720 802 419 (2012/06) · page 6 720 802 419 p.70; 6 720 643 409 p.87; 6 720 643 415 p.34 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026