Combined or separate?

Viessmann Vitodens 100-W 35 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 Viessmann Vitodens 100-W 35. Below 4 µA at steady state means clean or replace.

Only if the Viessmann Vitodens 100-W 35 is in warranty — Viessmann require log of any part swap for labour claims.

Renew the ignition and flame-sense electrodes on Viessmann Vitodens 100-W 35 when you get F27 / EA / L2 flame-detection faults after a clean burn.

Both electrodes on Viessmann Vitodens 100-W 35 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 Viessmann Vitodens 100-W 35 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?: Viessmann Vitodens 100-W 35 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 Viessmann Vitodens 100-W 35. Below 4 µA at steady state means clean or replace.
Do I need to notify the manufacturer?: Only if the Viessmann Vitodens 100-W 35 is in warranty — Viessmann require log of any part swap for labour claims.

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