Vaillant 100555 Flame Supervision Device

The Vaillant 100555 is a flame supervision device, the flame sensing electrode fitted in the burner area of Vaillant gas appliances. Its job is to detect whether a flame is actually present and to feed that signal back to the control board, which keeps the gas valve open only while combustion is proven. It is listed under the standard water heater category of Vaillant spares.

Flame sensing electrodes work alongside the separate ignition (spark) electrode. The ignition electrode creates the spark that starts combustion; the sensing electrode then confirms the flame and allows the appliance to run. The two are different components and are not interchangeable.

• The appliance locks out shortly after the ignition sequence, or fails to prove flame and closes the gas valve.
• Repeated lockouts that clear on reset but return on the next call for heat.
• The burner lights and then goes out, with the ignition sequence running again on the following attempt.
• A fault code relating to flame detection, flame loss or no flame signal.
• Visible soot, cracking or heat damage on the electrode tip, ceramic insulator or lead.

• Confirm the part number 100555 against the appliance data plate or the manufacturer's service documentation.
• Identify whether the fault lies with the ignition (spark) electrode or the flame sensing electrode, as they are separate parts.
• Inspect the electrode lead and its insulation, since a damaged or shorting lead can produce the same symptoms as a failed electrode.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.