What it is and what the ratings mean for the panel
The Siemens 5SL6425-7MB is a 4-pole SENTRON miniature circuit breaker (MCB) from the 5SL6 family, rated 25 A with a C tripping characteristic and a 6 kA breaking capacity per EN 60898 at 400 V AC. The C-curve means it trips at 5 to 10 times rated current — the standard choice for motor circuits, transformers, and lighting banks with moderate inrush, not for purely resistive loads where a B-curve would be tighter. The 6 kA rating is the maximum prospective fault current it can safely interrupt; in a residential or light commercial distribution board fed by a transformer of typical impedance, that covers most downstream faults without needing a current-limiting upstream device. The 4-pole configuration (4P) switches all three phases and the neutral, though the neutral conductor is not switched internally — it is a switched-neutral MCB, meaning the neutral pole opens and closes with the phases, which is required in some regional wiring rules for TN-S systems where the neutral is not bonded to ground at the board.
Physical fit and panel integration
The 5SL6425-7MB occupies 4 width units (72 mm) on a DIN rail, with a depth of 76 mm and a height of 90 mm. Installation depth is 70 mm, meaning the body extends that far behind the rail — important when the distribution board has a shallow backplate or cable ducts running behind the row. Terminal capacity accepts 0.75 mm² to 25 mm², which covers standard building wire from 1.5 mm² lighting circuits up to 6 mm² or 10 mm² feeder tails. The IP20 rating with connected conductors is typical for enclosed distribution boards; the breaker itself is not rated for wet or dusty environments. Mounting position is any, so it can be installed horizontally if the panel layout demands it, though derating may apply per the manufacturer's thermal data if airflow is restricted.