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F.447, F.448

F.447, F.448 — Burner in fault state: Deviation in ionization current signal

Viessmann · Vitodens 100-W Boiler

What does F.447, F.448 mean?

The burner is in a fault state due to a deviation in the ionization current signal. This indicates a problem with how the boiler detects the flame.

Common Causes

  • Deviation in ionization current signal
  • Faulty BCU burner control unit

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Reset the boiler by briefly turning off and on its power supply.

  2. 2

    If the fault recurs, contact a qualified heating engineer for further diagnosis.

  3. 3

    An engineer may need to replace the BCU burner control unit if the issue persists.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

Connection errorConnection error — Displayed on programming unitF.142F.142 — Burner in fault state due to CAN bus communication errorF.160F.160 — Burner in fault state due to CAN bus communication error
Source: Viessmann Vitodens 100-W Boiler
Open Manual (Page 80)Search more codes in this manual