Combined or separate?

Worcester Bosch Greenstar 24i 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 24i. Below 4 µA at steady state means clean or replace.

Only if the Worcester Bosch Greenstar 24i is in warranty — Worcester Bosch require log of any part swap for labour claims.

Renew the ignition and flame-sense electrodes on Worcester Bosch Greenstar 24i when you get F27 / EA / L2 flame-detection faults after a clean burn.

Both electrodes on Worcester Bosch Greenstar 24i use ceramic insulators — never re-use if chipped.

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.

Refill the Worcester Bosch Greenstar 24i 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.

Combined or separate?: Worcester Bosch Greenstar 24i 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 24i. Below 4 µA at steady state means clean or replace.
Do I need to notify the manufacturer?: Only if the Worcester Bosch Greenstar 24i is in warranty — Worcester Bosch require log of any part swap for labour claims.

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