Heat-pump-is-now-working-at-its-highest-permitted-temperature on a Worcester Bosch Greensource air to water heat pump: Info window: Heat pump is now working at its highest permitted temperature
Short answer
On a Worcester Bosch heat pump, Heat-pump-is-now-working-at-its-highest-permitted-temperature means: Info window: Heat pump 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: Heat pump is now working at its highest permitted temperature.
Part involved: T9 return sensor (~59 C limit).
When it shows: Heat setting too high; DHW temperature set too high; UFH/radiator valves closed; heat pump flow greater than system flow.
Likely causes:
- Heat setting too high; DHW temperature set too high; UFH/radiator valves closed; heat pump flow greater than system flow.
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 settings; open valves; check G1 vs G2 pump speed.
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
What owners and engineers report
3 owner and engineer reports mention this.
- Insufficient heating (house not warm enough) on the Greensource air to water heat pump (monobloc with HWDU): 3 reports
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