Heat pumps · Error codes · Worcester Bosch
5HWorcester Bosch · Greenstar Plus Hybrid (air to water heat pump + Worcester boiler)
5H on a Worcester Bosch Greenstar Plus Hybrid: Relay test was activated
Short answer
On a Worcester Bosch heat pump, 5H means: Relay test was activated. 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: Relay test was activated.
Part involved: hybrid control module / FW200.
When it shows: Relay test was activated.
Likely causes:
- Relay test activated (hybrid manager operating indicator).
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: yes.
Manual reset: Hold Back button on hybrid control module 5 s to restart after fault is rectified (installer).
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
- Check whether the boiler display also shows a fault (manual: if the boiler shows a fault the heat pump is not faulty) and report both to the engineer.
What the engineer will check
- Relay test activated (hybrid manager operating indicator).
Who to ask for: heat pump installer / controls engineer.
Certification: None specific; electrical isolation required before wiring checks.
Sources
- Installation and Maintenance Instructions Greenstar Plus Hybrid ↗ · 6 720 803 687 (2012/11) · page 57 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026