How to Replace the Ignition Electrode on a Worcester Bosch Greenstar 4000 30 (UK)
Step-by-step UK guide to replacing the spark / ionisation electrode on a Worcester Bosch Greenstar 4000 30. Part numbers, torques, commissioning.
The part
Renew the ignition and flame-sense electrodes on Worcester Bosch Greenstar 4000 30 when you get F27 / EA / L2 flame-detection faults after a clean burn.
Isolate safely
Both electrodes on Worcester Bosch Greenstar 4000 30 use ceramic insulators — never re-use if chipped.
Fit and commission
Set the spark gap to 3.5–4.0 mm and the ionisation gap so the tip sits 4–5 mm above the burner surface.
Recommission checklist
Refill the Worcester Bosch Greenstar 4000 30 to 1.2 bar cold. Bleed high-point radiators and the internal AAV.
Run a full flue-gas analysis after 15 minutes. Log the reading against the OEM commissioning envelope in the Benchmark book.
Frequently asked questions
- Combined or separate?
- Worcester Bosch Greenstar 4000 30 runs a two-electrode kit — one spark, one sense. Fit both together to avoid a second call-back.
- How do I test ionisation current?
- In service mode read the µA value on Worcester Bosch Greenstar 4000 30. Below 4 µA at steady state means clean or replace.
- Do I need to notify the manufacturer?
- Only if the Worcester Bosch Greenstar 4000 30 is in warranty — Worcester Bosch require log of any part swap for labour claims.
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