A01-5522 on a Worcester Bosch heat pump: Wrong combination of indoor and outdoor units
Short answer
On a Worcester Bosch heat pump, A01-5522 means: Wrong combination of indoor and outdoor units. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Wrong combination of indoor and outdoor units.
Part involved: I/O module / installer module coding.
When it shows: Wrong combination of indoor and outdoor units.
Likely causes:
- Non-matching heat pump and indoor unit; replaced I/O module in heat pump or installer module in indoor unit with rotary encoder not set correctly.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
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.
- 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
- Check combination tables; set rotary encoder to match old module/wiring diagram.
Who to ask for: heat pump installer / controls engineer.
Certification: None specific; electrical isolation required before wiring checks.
What you might notice
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