E21.E2 on a Worcester Bosch Greenstore LECP ground source heat pump: Faulty electric heater E21.E2
Short answer
On a Worcester Bosch heat pump, E21.E2 means: Faulty electric heater E21.E2. 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: Faulty electric heater E21.E2.
Part involved: electric additional heater.
When it shows: Overheat protection tripped, high flow temperature, too high heater temperature, or heater MCB tripped.
Likely causes:
- Overheat protection tripped, high flow temperature, too high heater temperature, or heater MCB tripped.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
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.
- Check the heating system pressure gauge reading (Bosch guidance is typically 1-2 bar when cold); report low pressure 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: Overheat protection tripped, high flow temperature, too high heater temperature, or heater MCB tripped.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
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 60 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026