error-dew-point-sensor-e1x-tm on an IVT Greenline HE: Activated when voltage 0-10V for temperature falls below 0.5V or exceeds 8V. Also activated when voltage 0-10V for humidity falls below 0.5V or exceeds 9.8V. Cooling on current mixing valve is aborted. The alarm may appear after a power failure but the alarm cause normally disappears automatically and the only thing that has to be done is to acknowledge the alarm
Short answer
On an IVT heat pump, error-dew-point-sensor-e1x-tm means: Activated when voltage 0-10V for temperature falls below 0.5V or exceeds 8V. Also activated when voltage 0-10V for humidity falls below 0.5V or exceeds 9.8V. Cooling on current mixing valve is aborted. The alarm may appear after a power failure but the alarm cause normally disappears automatically and the only thing that has to be done is to acknowledge the alarm. 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: Activated when voltage 0-10V for temperature falls below 0.5V or exceeds 8V. Also activated when voltage 0-10V for humidity falls below 0.5V or exceeds 9.8V. Cooling on current mixing valve is aborted. The alarm may appear after a power failure but the alarm cause normally disappears automatically and the only thing that has to be done is to acknowledge the alarm.
Part involved: E1x.TM.
When it shows: Activated when voltage 0-10V for temperature falls below 0.5V or exceeds 8V. Also activated when voltage 0-10V for humidity falls below 0.5V or exceeds 9.8V. Cooling on current mixing valve is aborted. The alarm may appear after a power failure but the alarm cause normally disappears automatically and the only thing that has to be done is to acknowledge the alarm.
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 sensor's value for temperature is 1V-7V and the sensor's value for humidity is 1-9.7V.
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. 29.
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-E17 (6 720 643 409 (2010/03)) ↗ · 6 720 643 409 (2010/03) · page 6 720 643 409 p.84; 6 720 643 415 p.28 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026