Add-heat-is-now-working-at-its-highest-permitted-temperature on a Worcester Bosch Greensource air to water heat pump: Info window: Add. heat is now working at its highest permitted temperature
Short answer
On a Worcester Bosch heat pump, Add-heat-is-now-working-at-its-highest-permitted-temperature means: Info window: Add. heat is now working at its highest permitted temperature. 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: Info window: Add. heat is now working at its highest permitted temperature.
Part involved: T9 return sensor (~58 C limit).
When it shows: Heat setting so high that return temperature is too high.
Likely causes:
- Heat setting so high that return temperature is too high.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Information only |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes.
Manual reset: Clears automatically; warnings may be acknowledged.
What you can check
- Read and note the full alarm text shown on the controller and pass it to your installer.
- Check thermostat / time program / operating mode settings on the controller.
What the engineer will check
- Reduce temperature setting.
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 Manual Air to Water Heat Pump with DHW distribution unit Greensource 6/7/9.5 kW ↗ · 6 720 641 467 (2010/01) · page 44 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026