The Siemens SIRIUS 3RU2126-1GB0 is a size S0 thermal overload relay, Trip Class 10, rated 690 V. It mounts directly onto a contactor — no separate base needed — and uses screw-type terminals for the main circuit. The integrated auxiliary switch signals a tripped condition (the part's own note reads "for message Tripped").
Ratings and what they mean for your panel
Class 10 means the relay must trip within 10 seconds at a 7.2× current overload — standard for protecting standard squirrel-cage motors during start-up. The 690 V rated value covers 400 V and 480 V systems with headroom; at 400 V the motor power rating is 2.2 kW, at 500 V it is 3 kW, and at 690 V it reaches 4 kW. Auxiliary contact ratings span the control voltage range: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V — so the same relay works across 24 VDC control circuits and 230 VAC contactor coils without a separate interface relay.
Mounting and wiring
Fastening method is contactor mounting — the relay clips onto the matching SIRIUS contactor without extra hardware. Mounting position is any orientation. The screw terminals accept 2 × (0.5 … 1.5 mm²) or 2 × (0.75 … 2.5 mm²) solid or stranded wire; use a Pozidriv PZ 2 tip with a 5–6 mm diameter shaft. Dimensions: 85 mm high, 45 mm wide, 85 mm deep — the S0 frame fits standard 45 mm-wide DIN-rail contactor footprints.
Environmental and compliance
Operating temperature range is –40 to +70 °C; storage and transport range is –55 to +80 °C. Temperature compensation is active from –40 to +60 °C, so the trip curve stays accurate across the typical panel ambient. The substance prohibitance date of 10/01/2009 aligns with early RoHS compliance milestones. MTTF with high demand rate is 2 280 years — a reliability figure for safety-instrumented-function assessments.