The Siemens 5SL1263-7MB is a SENTRON 5SL series miniature circuit breaker, 2-pole, C-curve, rated 63 A at 30 °C. Breaking capacity is 3 kA per IEC 60947-2 — that's the fault current it can safely interrupt without welding contacts or cascading upstream. The C-curve (5-10x In) means it handles moderate inrush from motor starters or transformer loads without nuisance tripping, while still clearing short circuits fast enough for most residential and light-commercial panels.
Panel fit and mounting
Width is 36 mm (2 modular units), depth 76 mm, installation depth 70 mm. Snaps onto standard DIN rail — any mounting position works, no derating for orientation. IP20 with conductors connected, so it's panel-internal only; no washdown exposure. Halogen-free and silicon-free construction matters if this goes into a clean room or a zone where off-gassing from a fault could damage nearby electronics.
What the ratings mean for your panel
The 3 kA breaking capacity (IEC 60947-2) is the ceiling for fault clearing — if your available fault current at the panel exceeds that, you need an upstream current-limiting device or a higher-rated breaker. Overvoltage category III and pollution degree 2 are standard for fixed-installation distribution boards. Mechanical service life is 4,000 switching cycles — fine for branch-circuit protection where it trips rarely, but not for frequent switching duty. The sealable design lets a panel builder or inspector lock the toggle position after commissioning.