The Siemens SIRIUS 3RT1916-2DG21 is a timing relay with an OFF-delay function — meaning the load remains energized for a set interval after the control signal drops. The adjustable time range spans 0.5 to 10 seconds, with a recovery time of 150 ms before the relay can accept the next trigger. Coil supply accepts 24 … 66 V at both AC (50/60 Hz) and DC, so it works across mixed-voltage control circuits without needing a separate DC supply module. The minimum ON period is 35 ms — short enough for pulse-triggered sequences but long enough to avoid chatter on a bouncing contact. The relay clips onto a DIN rail and fits any mounting position, which simplifies panel layout. Its 45 mm width matches the standard SIRIUS contactor footprint, so it aligns neatly alongside a 3RT2 contactor on the same rail.
Ratings and what they mean for fit
Pollution degree 3 means the relay is rated for conductive pollution environments — typical in industrial control panels where dust, condensation, or occasional conductive deposits are present. Basic insulation is sufficient for control-circuit isolation but not for mains-to-touch separation; the relay is intended for use within an enclosure, not as a standalone device. Wire termination accepts 2x (20 … 14) AWG solid or stranded — typical for control wiring up to 2.5 mm². The 38 mm depth and 38 mm height keep the relay shallow enough for shallow enclosures or tight gland-plate clearance.