T8-high-flow-temperature-or-T71-high-flow-temperature on a Worcester Bosch Greensource Split HP Hydrolight / Hydrocomfort: Alarm: T8 high flow temperature or T71 high flow temperature
Short answer
On a Worcester Bosch heat pump, T8-high-flow-temperature-or-T71-high-flow-temperature means: Alarm: T8 high flow temperature or T71 high flow temperature. 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: Alarm: T8 high flow temperature or T71 high flow temperature.
Part involved: T8/T71 flow sensors.
When it shows: Insufficient flow (heat carrier pump stopped, valves closed, pump speed); blocked filter.
Likely causes:
- Insufficient flow (heat carrier pump stopped, valves closed, pump speed); blocked filter.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Acknowledge by pressing the rotary selector (Acknowledge) on the Hydrolight/Hydrocomfort user interface.
What you can check
- Read and note the full alarm text shown on the controller and pass it to your installer.
- Acknowledge the alarm once on the control panel; if it returns, call the installer.
What the engineer will check
- Check pump, valves, speeds; clean filter (22.1).
Who to ask for: heat pump installer / heating engineer.
Certification: None specific for hydraulic checks; MCS-certified installer recommended for system changes.
What you might notice
Sources
- Installation, Commissioning and Servicing Instructions Greensource Hydrolight and Hydrocomfort (ODU 7.5-12) ↗ · 6 720 806 629 (2013/02) · page 65 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026