What it is — and what the ratings mean for fit
The Siemens 3RV6021-4PA15 is a SIRIUS S0-frame motor protection circuit breaker rated 36 A operational current with a thermal-magnetic trip in Class 10. Class 10 means it trips within 10 seconds at 7.2× rated current — that's fast enough to protect a standard induction motor during a locked-rotor event without nuisance tripping on normal start-up. The 36 A rating at AC-3 (motor switching) covers motors up to roughly 15 kW at 400 V, depending on full-load amps. Rated voltage goes to 690 V, so it handles 480 V and 600 V class line-ups without derating. The thermal overload release handles the running protection; the magnetic short-circuit trip clears faults fast. It's current production and mounts on 35 mm DIN rail per DIN EN 60715 — snap-on or screw-fixed, any orientation.
Panel fit and wiring
S0 frame footprint: 45 mm wide, 97 mm tall, 96 mm deep. That's a standard three-pole MCCB width — fits most DIN-rail enclosures without surprises. Clearance: 70 mm above and below, 30 mm to the sides; zero forward or backward clearance needed. Main-circuit terminals accept 2x (0.5…1.5 mm²) solid/stranded or 2x (0.75…2.5 mm²) — AWG equivalents 2x (16…12) and 2x (14…8). Auxiliary terminals are 2x (0.5…1.5 mm²) or 2x (0.75…2.5 mm²) — AWG 2x (20…16) and 2x (18…14). Screw terminals on both main and auxiliary circuits; torque to 2…2.5 N·m on the main contacts. Wire it with ferruled stranded or solid — no special crimp tool needed. The transverse auxiliary switch design means the contact block sits alongside the breaker, not stacked on top, keeping the overall height low.