Maximum-working-temperature-additional-heat on a Worcester Bosch Greensource Split HP Hydrolight / Hydrocomfort: Info: Maximum working temperature additional heat
Short answer
On a Worcester Bosch heat pump, Maximum-working-temperature-additional-heat means: Info: Maximum working temperature additional heat. 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: Maximum working temperature additional heat.
Part involved: CH return limit.
When it shows: Heating curve too high; bivalence point incorrectly set.
Likely causes:
- Heating curve too high; bivalence point incorrectly set.
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: Info symbol clears once read.
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
- Adjust heating curve/bivalence.
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 67 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026