Heat pumps · Error codes · IVT
GT8IVT · Greenline HT Plus
GT8 on an IVT Greenline HT Plus: Heat transfer fluid out max T8 (GT8): the safety sensor stops the compressor because the water going out to the radiators is too hot
Short answer
On an IVT heat pump, GT8 means: Heat transfer fluid out max T8 (GT8): the safety sensor stops the compressor because the water going out to the radiators is too hot. 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: Heat transfer fluid out max T8 (GT8): the safety sensor stops the compressor because the water going out to the radiators is too hot.
Part involved: flow sensor GT8.
Likely causes:
- Not enough flow over the heat pump; particle filter on hot side clogged.
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
- Check the heating-system pressure gauge is in the range given in the user guide (Thermia/Danfoss: 1-1.5 bar when cold) - do not top up yourself unless you have been shown how; check radiator/underfloor valves and room thermostats are open. Press the Ackn. button on the control panel once (the manual says there is no risk in resetting an alarm; the heat pump restarts within 15 minutes if heat is needed). If the alarm returns, contact your installer.
What the engineer will check
- Check pump and valves; clean particle filter. Restarts automatically when the alarm is reset and temperature normal.
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.38 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026