failure-on-sensor-e12-t1-e13-t1-flow on an IVT Greenline HE: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The mixing valve for the circuit is closed completely
Short answer
On an IVT heat pump, failure-on-sensor-e12-t1-e13-t1-flow means: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The mixing valve for the circuit is closed completely. 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 mixing valve for the circuit is closed completely.
Part involved: E12.T1.
When it shows: The alarm is activated when the sensor's value indicates a temperature lower than 0 °C. The mixing valve for the circuit is closed completely.
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