Maximum-working-temperature-heat-pump on a Worcester Bosch Greensource Split HP Hydrolight / Hydrocomfort: Warning: Maximum working temperature heat pump
Short answer
On a Worcester Bosch heat pump, Maximum-working-temperature-heat-pump means: Warning: Maximum working temperature heat pump. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Warning: Maximum working temperature heat pump.
Part involved: T9 return (>56 C).
When it shows: Heat setting too high; UFH/radiator valves closed; heat pump flow higher than system flow.
Likely causes:
- Heat setting too high; UFH/radiator valves closed; heat pump flow higher than system flow.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: yes.
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.
- Check thermostat / time program / operating mode settings on the controller.
What the engineer will check
- Reduce heat setting; open valves; check pump speeds (20.3).
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 66 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026