What This Part Is and Where It Fits
The Siemens 3RB1036-2UB0 is a solid-state overload relay in the SIRIUS family, rated 15...50 A with class 20 trip characteristic. It mounts directly onto a contactor of size S2, using screw terminals for the power and control wiring. The manual-automatic reset selector gives the commissioning engineer a choice: manual reset for attended installations where a fault must be acknowledged, or automatic reset for remote or unmanned sites where the motor restarts after the overload cools.
What the Ratings Mean for Fit
The 15...50 A range covers a wide band of motor FLA values, but the class 20 trip curve is the key selection parameter. Class 20 means the relay will trip within 20 seconds at 600% of the set current — standard for general-purpose induction motors driving pumps, fans, and conveyors where moderate start-up times are expected. If the motor drives a high-inertia load with a long acceleration ramp, class 30 might be needed; for short-stall protection on a crusher, class 10 is tighter. The size S2 mounting footprint matches Siemens 3RT2 contactors in the same frame size, so the assembly clips together without additional hardware.