Hxx on a Worcester Bosch heat pump: Maintenance message, e.g. service interval of heat source elapsed
Short answer
On a Worcester Bosch heat pump, Hxx means: Maintenance message, e.g. service interval of heat source elapsed. 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: Maintenance message, e.g. service interval of heat source elapsed.
Part involved: service reminder.
When it shows: Maintenance message, e.g. service interval of heat source elapsed.
Likely causes:
- Service interval of heat source elapsed.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: Clears when cause is removed.
Manual reset: User guides (7001i/7400i AWE, 3400i AWS, section 3.5): user may confirm the fault by pressing the selector; if it persists call the contractor with fault code, sub-code and user-interface ID no.
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
- Arrange the annual service with your installer.
- Confirm/acknowledge the fault once at the controller (press selector) as the user guide allows; if it returns, call the installer.
What the engineer will check
- Carry out service per heat source documentation.
Who to ask for: heat pump installer / heating engineer.
Certification: None specific for hydraulic checks; MCS-certified installer recommended for system changes.
Sources
- Installation instructions User interface HPC 410 ↗ · 6721832682 (2021/02) · page 19 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026