What this MCB is and what it does
The Siemens SENTRON 5SL4308-7 is a 3-pole miniature circuit breaker (MCB) with a C-trip curve, rated 8 A at 400 V AC and a 10 kA breaking capacity per EN 60898. The C-curve means it trips between 5 and 10 times rated current — suited for mixed resistive and moderate inductive loads like lighting circuits, small motor starters, and general-purpose distribution in residential and light commercial panels.
Key ratings and what they mean for fit
Rated 8 A at 30 °C ambient; at 40 °C the continuous current derates to 7.39 A, at 45 °C to 7.04 A, and at 55 °C to 6.37 A. If the panel runs warm, size the branch circuit for the derated value — the 8 A label is only valid at the 30 °C reference. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2 — that's the fault current this MCB can safely interrupt without welding contacts or rupturing the case. For installations where the prospective short-circuit current exceeds 10 kA, step up to a higher-rated device or add a current-limiting upstream fuse. Rated insulation voltage is 440 V AC for multi-phase operation; the supply frequency is 50/60 Hz. Overvoltage category III and pollution degree 2 cover fixed-installation distribution boards — typical for main or sub-distribution panels. Mechanical service life is 10 000 switching cycles — adequate for normal overcurrent protection duty but not intended for frequent manual switching as a load-break device.
Mounting and integration
Occupies 3 modular width units (54 mm) on a DIN rail. Depth is 76 mm, installation depth 70 mm. Mounting position is unrestricted — horizontal, vertical, or any angle works. IP20 with connected conductors — protected against finger contact but not against water ingress, so it's for indoor enclosures only. Sealable design allows the installer to lock the toggle position with a padlock — useful for lockout/tagout on dedicated circuits. Halogen-free and silicon-free construction reduces toxic smoke and corrosive byproducts in case of arc fault inside the panel.