A22-1001 on a Worcester Bosch heat pump: BUS signal from the higher-level user interface for remote control is missing (A22: heating circuit 2 ... A28: heating circuit 8)
Short answer
On a Worcester Bosch heat pump, A22-1001 means: BUS signal from the higher-level user interface for remote control is missing (A22: heating circuit 2 ... A28: heating circuit 8). 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: BUS signal from the higher-level user interface for remote control is missing (A22: heating circuit 2 ... A28: heating circuit 8).
Part involved: EMS BUS to system controller.
When it shows: BUS signal from the higher-level user interface for remote control is missing (A22: heating circuit 2 ... A28: heating circuit 8).
Likely causes:
- Higher-level UI missing or BUS not connected.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Clears when cause removed.
Manual reset: CR 10 H manual: if a fault cannot be rectified note fault code and sub-code and contact contractor with 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.
What the engineer will check
- Install higher-level UI (e.g. CW 400); establish BUS connection.
Who to ask for: heat pump installer / controls engineer.
Certification: None specific; electrical isolation required before wiring checks.
What you might notice
Sources
- CR 10 H room controller manual (multilingual) ↗ · 6720876740 (2017/08) · page 29 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026