the-heat-pump-is-now-working-in-anti-freeze-mode on an IVT Greenline HE: Activated when the flow temperature of a circuit falls below 8° C a n d t h e 1 0 - m i n t i m e r h a s c o u n t e d d o w n
Short answer
On an IVT heat pump, the-heat-pump-is-now-working-in-anti-freeze-mode means: Activated when the flow temperature of a circuit falls below 8° C a n d t h e 1 0 - m i n t i m e r h a s c o u n t e d d o w n. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Activated when the flow temperature of a circuit falls below 8° C a n d t h e 1 0 - m i n t i m e r h a s c o u n t e d d o w n .
When it shows: Activated when the flow temperature of a circuit falls below 8° C a n d t h e 1 0 - m i n t i m e r h a s c o u n t e d d o w n .
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: Yes - The circuit's flow temperature exceeds 25 °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. 33. Check the heating-system pressure gauge is in the range given in the user guide - do not top up yourself unless you have been shown how; check radiator/underfloor valves and room thermostats are open.
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.88; 6 720 643 415 p.32 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026