The Siemens SENTRON 3VA1150-5EF36-0BH0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current of 50 A at 40 °C ambient with no derating needed up through 50 °C — at 55 °C it still holds 49 A, and at 70 °C it's at 45 A, so it handles warm panel interiors without a frame size bump. The interrupting ratings tell the real story: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V.
Plan for 70 mm of clearance behind the panel door for the body depth plus wiring space.
