The Siemens 3RU2126-1HC0 is a SIRIUS thermal overload relay, size S0, designed to protect motors against overcurrent and phase failure. It is rated for a maximum operating voltage of 690 V and carries a CLASS 10 trip characteristic, meaning it will trip within 10 seconds at 7.2× the current setting — standard for general-purpose motor starting where the start-up transient is brief. The relay mounts directly onto a contactor (fastening method: contactor mounting) and can be installed in any position. The main current circuit uses spring-loaded terminals, accepting 2× (0.5 to 2.5 mm²) solid or stranded wire, which speeds panel wiring and reduces the risk of loose connections under vibration. Auxiliary switching is integrated — the relay includes a built-in auxiliary switch that changes state on trip, providing a signal for the control system. The note "for message 'Tripped'" indicates this switch is intended to drive a status indication or interlock rather than direct load switching.
Environmental & 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, ensuring the trip curve stays accurate across the working range. The relay is RoHS-compliant per the substance prohibition date of 10/01/2009.