What it is and what it does
The Siemens 5SL6320-7BB is a SENTRON miniature circuit breaker (MCB) — 3-pole, C-curve, rated 20 A at 400 V AC, with a 6 kA breaking capacity per EN 60898 and IEC 60947-2. That C-curve means it trips between 5 and 10 times rated current, so it's the standard choice for general-purpose loads like lighting, socket circuits, and small motor feeders in residential and infrastructure panels. The 6 kA rating at 400 V tells you it can safely interrupt a fault current up to that level without welding contacts or cascading upstream — adequate for most domestic and light commercial distribution boards.
Thermal derating and real-world current
The 20 A rating holds at 30 °C ambient. At 40 °C it derates to 18.94 A, at 45 °C to 18.4 A, and at 55 °C to 17.24 A. If your panel runs hot — say a crowded enclosure near a boiler or in a sunny switchroom — you need to account for that drop. The breaker is rated for pollution degree 2 (normal, non-conductive dust) and overvoltage category III (fixed installation downstream of the main panel).
Physical fit and panel integration
Occupies 3 modular width units (54 mm wide) on a DIN rail. Depth is 76 mm, installation depth 70 mm. Snap-on mounting, any position. Touch protection is built in. Sealable — useful if you need to lock out settings after commissioning. Halogen-free and silicon-free, so it's safe for use in clean environments or where outgassing matters.