failure-on-sensor-e11-t1-flow on an IVT Greenline HE: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The flow temperature T1 becomes identical to T8. If there are several heat pumps installed, T1 = T8 for the heat pump that does not produce hot water and has the highest value on T8. Additional heat mixing valve shut
Short answer
On an IVT heat pump, failure-on-sensor-e11-t1-flow means: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The flow temperature T1 becomes identical to T8. If there are several heat pumps installed, T1 = T8 for the heat pump that does not produce hot water and has the highest value on T8. Additional heat mixing valve shut. 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 alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The flow temperature T1 becomes identical to T8. If there are several heat pumps installed, T1 = T8 for the heat pump that does not produce hot water and has the highest value on T8. Additional heat mixing valve shut.
Part involved: E11.T1.
When it shows: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The flow temperature T1 becomes identical to T8. If there are several heat pumps installed, T1 = T8 for the heat pump that does not produce hot water and has the highest value on T8. Additional heat mixing valve shut.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Yes - The value of the sensor indicates >0 °C.
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. Contact the dealer if the alarm remains active for more than three hours or recurs often.
What the engineer will check
- Measure sensor and cable resistance against the IVT sensor table; check connections on the I/O board; replace sensor or cable.
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.68; 6 720 643 409 p.85; 6 720 643 415 p.29 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026