De Dietrich 85757743 3-way Ventiloption FM48

This article is an electronic control board (PCB) for a wall-hung boiler, listed under the De Dietrich brand. Parts of this type serve as the burner control, managing the entire ignition and safety sequence: pre-purge, ignition, fuel admission, flame proving, and lockout on failure. The board reads signals from pressure switches, flame detectors (ionisation or UV/IR), and temperature sensors, and drives the ignition transformer, gas valve, fan, and additional components such as a circulating pump or three-way valve. The model designation and the term “3-way valve option” indicate that this board includes the circuitry to control a diverter or zone valve, common in combi or system boilers that switch between heating and hot water. Selection of such a control board is strictly by the boiler model and series. Even within the same brand, boards with different safety times, supply voltages, or base patterns are not interchangeable. A mismatched control can result in unsafe operation, such as delayed lockout or improper purge durations. When replacing, always verify the exact part number—here given as 85757743 and 336.568.015—against the boiler’s documentation. The board is typically mounted in the electrical compartment and connects via a dedicated plug pattern; ensure compatibility of the harness and any external controls. No further technical specifications are available for this specific item beyond its catalogue identity.