SIRIUS 3RV2031-4UB15 — motor protection circuit breaker
The Siemens SIRIUS 3RV2031-4UB15 is a motor protection circuit breaker designed for protecting three-phase induction motors against overload and short-circuit conditions. It mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 60715, fitting into any standard control panel enclosure. Rated Trip Class 20, meaning it allows a motor to draw up to 20 times its full-load current for 20 seconds before tripping — appropriate for loads with moderate starting inertia like conveyors, pumps, and compressors. The breaker includes phase failure detection, which will trip if one phase is lost, preventing single-phasing damage to the motor. Breaking capacity is 30 kA at 400 V AC, with a higher 100 kA at 240 V. The 30 kA figure at 400 V is the rating that governs coordination with upstream protection in a 400 V three-phase panel — it must be matched to the available fault current at the installation point. The voltage range spans 20 to 690 V, covering standard low-voltage motor circuits.
Dimensions and mounting
Width is 55 mm, depth 149 mm, height 140 mm. The 55 mm width occupies three 18 mm modular spaces on a DIN rail — a standard footprint for this class of motor-protective device. Clearance requirements: 50 mm above and below for air circulation and arc venting, 10 mm at the sides. Mounting position is any orientation, which simplifies panel layout when space is constrained. Main contact terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire — sized for motor feeder cables up to 2.5 mm².