The Siemens 3RV2021-0JA25 is a SIRIUS motor-protective circuit breaker designed for motor protection with CLASS 10 trip characteristics, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect a standard induction motor during a locked-rotor start but slow enough to ride through normal acceleration. Rated breaking capacity hits 100 kA at 400 V AC (and at 240 V, 500 V, and 690 V), so this breaker can safely interrupt fault currents up to that level without upstream fusing in most industrial panels — a key spec for high-fault-capacity installations. At 45 mm wide, it occupies a single 45 mm slot on the rail — standard for this class of motor-protective device.
The depth is the critical fit dimension for enclosure depth — 97 mm clears most standard shallow enclosures (100 mm minimum internal depth), but verify your gland plate and busbar clearance. Terminals are spring-loaded for the main current circuit, accepting 2× (0.5 to 2.5 mm²) solid or stranded. No screw torque to verify on the spring-cage side; strip length and ferrule size are the only variables. Auxiliary contact space is available on the side. Clearance distances: 50 mm upwards and downwards, 30 mm at the side, 0 mm forwards and backwards. The zero forward/backward clearance means it can be mounted flush against a backplate or panel door — no extra breathing space needed in those axes.
Storage and transport range: -50 to +80 °C.
Ratings and selection notes
Ground fault detection is not included; if that's required, add an external ground-fault module or specify a different variant. Rated operational voltage range: 20 to 690 V AC. Power ratings: 0.2 kW at 230 V, 0.5 hp at 575/600 V. Auxiliary contact ratings: 1 A at 24 V, 0.5 A at 120/125/230 V, 0.15 A at 60 V — these are the dry-contact switching limits for the integrated auxiliary contacts. Maximum switching frequency at AC-3 duty: 15 operations per hour. That's the thermal limit for motor starting — fine for pump or fan cycling, but not for high-repetition applications like stamping presses or rapid indexing.