faulty-external-additional-heat-e71-e1-e1-f21 on an IVT Greenline HE: External additional heat refers to additional heat which is controlled as mixed additional heat or via 0-10V signal. If the alarm signal from the additional heat has been connected to 10 - C on the PEL board, the alarm can be given when an error occurs. The type of error depends on the connected unit
Short answer
On an IVT heat pump, faulty-external-additional-heat-e71-e1-e1-f21 means: External additional heat refers to additional heat which is controlled as mixed additional heat or via 0-10V signal. If the alarm signal from the additional heat has been connected to 10 - C on the PEL board, the alarm can be given when an error occurs. The type of error depends on the connected unit. 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: External additional heat refers to additional heat which is controlled as mixed additional heat or via 0-10V signal. If the alarm signal from the additional heat has been connected to 10 - C on the PEL board, the alarm can be given when an error occurs. The type of error depends on the connected unit.
Part involved: E71.E1.E1.F21.
When it shows: External additional heat refers to additional heat which is controlled as mixed additional heat or via 0-10V signal. If the alarm signal from the additional heat has been connected to 10 - C on the PEL board, the alarm can be given when an error occurs. The type of error depends on the connected unit.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Manual reset: Acknowledge on control panel.
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. Acknowledge once on the control panel; if the alarm returns, contact the installer.
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-E17 (6 720 643 409 (2010/03)) ↗ · 6 720 643 409 (2010/03) · page 6 720 643 409 p.84 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026