Heat pumps · Error codes · Worcester Bosch
E1X.TT-commWorcester Bosch · Greenstore LECP ground source heat pump (System & Combi)
E1X.TT-comm on a Worcester Bosch Greenstore LECP ground source heat pump: Check connection to room sensor E1X.TT (room controller)
Short answer
On a Worcester Bosch heat pump, E1X.TT-comm means: Check connection to room sensor E1X.TT (room controller). 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: Check connection to room sensor E1X.TT (room controller).
Part involved: room controller.
When it shows: Communication with room controller terminated.
Likely causes:
- Communication with room controller terminated.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: no.
Manual reset: Acknowledgement required.
What you can check
- Read and note the full alarm text and category letter shown on the controller and pass it to your installer.
- Acknowledge the alarm on the control unit once (the manual allows acknowledgement); if it recurs call the installer.
What the engineer will check
- Diagnose per chapter 21: Communication with room controller terminated.
Who to ask for: heat pump installer / controls engineer.
Certification: None specific; electrical isolation required before wiring checks.
What you might notice
Sources
- Installation, Commissioning and Servicing Instructions Worcester Greenstore LECP GSHP (System/Combi 6-11 kW) ↗ · 6 720 806 768 (2013/02) · page 63 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026