What it is and what it does
The Siemens 3RU2126-1EB0-ZX95 is a SIRIUS thermal overload relay in the Size S0 frame, designed to protect motors against overcurrent and phase-loss conditions by monitoring the motor current and tripping the associated contactor when an overload is detected. Trip Class 10 means the relay will trip within 10 seconds at 7.2 times the set current — fast enough to protect standard induction motors during locked-rotor or prolonged start-up events without nuisance tripping on normal starts. The thermal bimetal release mechanism compensates for ambient temperature changes from -40 to +60 °C, so the trip curve stays accurate whether the relay is in a heated control room or a cold warehouse.
Integration and mounting
Mounts directly onto the contactor via the fastening method — no separate DIN-rail clip needed, which saves a panel row. The 45 x 85 x 85 mm footprint matches the SIRIUS S0 contactor outline. Screw-type terminals on the main current circuit accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire. A Pozidriv PZ 2 screwdriver with 5 to 6 mm shaft diameter is specified for termination. Mounting position is unrestricted — any orientation works, which simplifies layout in tight enclosures.
Auxiliary contact ratings and signal feedback
An integrated auxiliary switch provides remote trip indication — the Note "for message Tripped" on the order code signals that this variant includes a dedicated contact to report the overload state to a PLC or annunciator. The auxiliary contact is rated for switching: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. At lower DC voltages it handles 0.3 A at 60 V and 0.22 A at 110/125/220 V — sufficient for most 24 VDC control circuits.