Heat pumps · Error codes · IVT
GT11IVT · Greenline HT Plus
GT11 on an IVT Greenline HT Plus: HTF out under limit T11 (GT11): brine temperature out of the heat pump below the limit
Short answer
On an IVT heat pump, GT11 means: HTF out under limit T11 (GT11): brine temperature out of the heat pump below the limit. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: HTF out under limit T11 (GT11): brine temperature out of the heat pump below the limit.
Part involved: brine-out sensor GT11.
Likely causes:
- As GT10: temporary low brine temperature; low cold-side flow; minimum brine temperature set too low; groundwater filter/pump problems.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Yes.
What you can check
- Wait and see - if the alarm returns, contact your dealer. Look at the brine expansion tank: the fluid level should be visible (user guide check). Do not refill or open the ground-loop circuit yourself - call the installer.
What the engineer will check
- As GT10.
Who to ask for: heat pump engineer.
What you might notice
Sources
- Greenline HT Plus C and E Guide to installation, commissioning and maintenance (Art. no 290410-29, v1.1) ↗ · 290410-29 v1.1 · page p.39 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026