The Siemens 3RU2126-1DJ0 is a SIRIUS thermal overload relay in the S0 frame size, designed for contactor mounting to protect three-phase motors. Its Class 10 trip characteristic means it opens within 10 seconds at 7.2× the set current at operating temperature — the standard for standard-start induction motors, not for high-inertia loads that need a slower Class 20 or 30. Rated insulation voltage is 690 V, with power ratings of 1.1 kW at 400 V, 1.5 kW at 500 V, and 2.2 kW at 690 V. The integrated auxiliary switch provides signal feedback across the control voltage range: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. Temperature compensation is active from -40 to +60 °C, and the relay operates across -40 to +70 °C ambient. The S0 footprint and contactor-mounting fastening mean it clips directly onto the matching Siemens contactor — no separate panel space needed, and the ring cable lug connection on the main circuit handles the motor leads.
Mounting and Integration
Mounts directly onto the matching Siemens contactor via the contactor-mounting fastening — no DIN rail or separate bracket required. The S0 size mates with the S0 contactor frame. Screw terminals on the main circuit accept ring cable lugs; auxiliary connections use M4 screws with a Pozidriv PZ 2 tip, 5–6 mm shaft diameter. Mounting position is any orientation, which simplifies panel layout. The integrated auxiliary switch eliminates the need for a separate add-on block for the tripped signal.
Environmental and Compliance
Storage and transport temperature range is -55 to +80 °C; operating range is -40 to +70 °C. The substance prohibitance date of 10/01/2009 aligns with RoHS compliance. MTTF with high demand rate is 2,280 years.