The Siemens 3RU2136-4JB0 is a SIRIUS thermal overload relay in size S2, designed for motor protection with CLASS 10 trip characteristics and a rated voltage of 690 V. It nails the cure recipe for standard motor starts — fast enough to protect the winding during locked-rotor conditions but no nuisance trips on normal acceleration.
Ratings and real-world fit
The integrated auxiliary contact is labeled "for message Tripped"; it closes when the bimetal strip deflects, giving a dry-contact signal back to a PLC or alarm beacon. Wire the contact per the 2x (0.5–1.5 mm²) or 2x (0.75–2.5 mm²) screw-terminal capacity — same terminals used for the main power circuit. Temperature compensation operates from -40 to +60 °C, so the trip curve stays accurate even when the relay is near a hot contactor or under a sunlit panel roof. Storage range extends from -55 to +80 °C, but that's a handling spec, not an operating condition.
Mounting and mechanical data
Fastens directly onto a SIRIUS S2 contactor — no separate DIN-rail adapter needed. The 55 mm width, 90 mm height, and 105 mm depth match the contactor footprint exactly, so a line-down swap takes minutes. Screw terminals accept Pozidriv PZ 2 bits with a 5–6 mm shaft diameter; torque to the ratings printed on the relay housing.