Motor protection circuit breaker for panel integration
The Siemens SIRIUS 3RV2021-1JA25 is a motor protection circuit breaker designed for the main current circuit, with a Trip Class 10 rating that means it will trip within 10 seconds at 7.2× the thermal setting — standard for protecting standard induction motors during start-up without nuisance tripping. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, with a 45 mm width that takes up a single 45 mm slot in the panel — important for density planning in a crowded enclosure. The main circuit uses spring-loaded terminals accepting 2× (0.5 to 2.5 mm²) solid or stranded wire, so no screw torqueing required on the line and load connections.
Breaking capacity and fault current coordination
Rated breaking capacity hits 100 kA at 240 V and 400 V, dropping to 42 kA at 500 V and 4 kA at 690 V — the 100 kA figure at 400 V means it can safely interrupt high fault currents typical in industrial distribution without needing an upstream current-limiting fuse for most installations. Phase failure detection is built in, so the breaker will trip on loss of one phase — preventing single-phasing damage to the motor. No ground fault detection on this variant — if that's required, look at the 3RV2021-4CA25 or 4NA25 which carry that function.
Dimensions and mounting clearances
The device measures 45 mm wide, 119 mm high, and 97 mm deep — the 97 mm depth is the dimension from the DIN rail mounting surface to the front of the housing, so verify enclosure depth clearance before panel layout. Required clearances around the breaker: 50 mm upwards and downwards, 30 mm at the sides, and 0 mm forwards and backwards — meaning it can be mounted flush against the back panel and enclosure door, but needs breathing space above and below for arc venting and heat dissipation. Mounting position is any orientation, so horizontal or vertical DIN rail mounting works without derating.