EK on a Worcester Bosch Greenstore ground source heat pump: Electric heater (EK)
Short answer
On a Worcester Bosch heat pump, EK means: Electric heater (EK). 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: Electric heater (EK).
Part involved: electric heater MCB (circuit-breaker 3) / overheat protection (4).
When it shows: Electric heater (EK).
Likely causes:
- Electric heater MCB tripped; overheat protection tripped (most often poor primary flow, air or blocked filter).
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: Press Ackn. on the control panel; heat pump restarts within 15 minutes if there is demand. Some causes need a reset button/MCB on the heat pump (engineer).
What you can check
- Read and note the full alarm text and code in brackets 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.
- Press the Ackn. button once as the manual describes (manual: no risk in resetting an alarm); contact technical support if the alarm repeats.
What the engineer will check
- Reset MCB/overheat protection on heat pump; check filter and primary flow.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Unexpected backup / auxiliary heater use on the Greenstore ground source heat pump (original, System & Combi): 1 report
Sources
- Worcester Greenstore 6/7/9/11 kW System Installation, Commissioning & Servicing ↗ · 8-716-112-860 Issue c · page 36 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026