Sit Control box 503 EFD 0.503.103

This is a Sit 503 EFD control box, an OEM equivalent to part 0020025227. It is designed for use in a Protherm RKC23 burner controller. The unit manages the burner's ignition and safety sequence: it initiates pre-purge, energizes the ignition transformer, opens the fuel valve, and verifies flame presence within the defined safety time. It also monitors the air pressure switch and other safety devices, and will initiate a lockout when a fault is detected.

When choosing a replacement for a control box of this kind, match the exact series and type designation, supply voltage, required safety times (pre-purge and flame-establishment), and the flame‑detection method (ionisation, UV, or IR). The physical connection pattern (base or plug) must be compatible with the existing wiring. Use only a unit with the same series and safety time settings; different series from the same brand are generally not interchangeable. Verify markings on the existing control and consult the burner or boiler technical documentation before ordering.