Sit Gas valve 845 SIGMA 0.845.057

The Sit 845 SIGMA gas valve, SKU 0.845.057, is a gas valve manufactured by Sit. It is designed for use in Beretta boilers, specifically the Mynute, Exclusive, Ciao, and City models. This valve shuts off and meters the gas supply to the burner, opening on command from the burner control and only when the gas pressure switch permits. In premix boilers, it operates with a pneumatic gas/air link tied to the fan.

When selecting a replacement gas valve of this type, key parameters include the brand and series, connection size (typically Rp 1/2" to 2" or flanged), coil voltage (usually 230 V or 24 V AC/DC), and required function (single or double solenoid, slow opening, servo-regulated, or multiblock with filter and regulator). Verify the electrical supply and mechanical interface before ordering. The coil is often replaceable separately from the valve body, which may allow a lower-cost repair if the coil alone is faulty.

Common failure modes for gas valves of this type include coil burnout, leaking valve seat, drifting outlet pressure, and a seized servo regulator. When these occur, the equipment may fail to ignite, shut down unexpectedly, or exhibit unstable burner operation. Check the coil continuity, valve seat sealing, and outlet pressure regulation to diagnose the issue.