What it is and what it does
The Siemens 3RT1916-2EJ31 is a SIRIUS auxiliary switch with an adjustable ON-delay function, designed to clip onto a contactor or relay base. It provides a timed auxiliary contact that closes after a set delay when the main device picks up. The delay is adjustable from 5 to 100 seconds, set via a potentiometer or DIP switch on the module. The ON-delay means the contact closes after the delay period once the coil is energized; there is no OFF-delay function.
Key ratings and what they mean for fit
The auxiliary contact is rated 1 A at 24 V DC, 0.2 A at 125 V DC, and 0.1 A at 250 V DC. These are the switching capacities for DC loads — the current drops as voltage rises because of arc extinction limits. For a 24 V DC control circuit, the contact can handle 1 A, which covers most PLC digital inputs and relay coils. The switch is rated for basic insulation and pollution degree 3, meaning it's suitable for industrial environments where conductive dust or condensation may occur. The IP20 terminal protection means it's safe from finger contact but not from water ingress — install inside a panel. It mounts via clip-on to a DIN rail or directly onto a SIRIUS contactor. The dimensions are 45 mm wide, 38 mm high, and 75 mm deep, so it occupies one standard modular width. The wire terminals accept solid or stranded conductors from 18 to 14 AWG.
Where it's used
This auxiliary switch is used in motor control centers and panel builds where a delayed auxiliary contact is needed — for example, to sequence a star-delta starter, delay a fan start after a pump, or interlock a secondary process. The clip-on form factor means it integrates directly onto a SIRIUS contactor without extra wiring.