What the ratings mean for fit
The Siemens SENTRON 5SL3240-7MB is a 2-pole miniature circuit breaker rated 40 A at 400 V AC with a C tripping characteristic and a 4.5 kA breaking capacity per EN 60898. The C-curve means it trips between 5 and 10 times rated current — standard for inductive and motor-start loads where inrush is moderate, like pumps, fans, or small compressors in residential and infrastructure panels. The 4.5 kA interrupting rating at 400 V AC tells you it can safely clear a fault up to that level without upstream damage; if your available fault current exceeds that, you need a current-limiting upstream device or a higher-rated breaker. The 2-pole design switches both phase and neutral (or two phases) in a single 36 mm wide unit, occupying 2 modular width units on the DIN rail.
Panel integration notes
Mounts on a standard 35 mm DIN rail in any position — no derating for orientation. The 76 mm depth and 70 mm installation depth fit standard distribution boards; the 36 mm width (2 modular units) means it occupies two adjacent 18 mm slots. IP20 with connected conductors is typical for enclosed panel use — no special sealing needed. The housing is halogen-free and silicon-free, which matters for environments sensitive to outgassing (clean rooms, certain industrial zones). Sealable design allows padlocking the handle in the OFF position for lockout/tagout compliance.
Environmental and compliance
Rated for ambient temperatures from -40 °C to 75 °C, with the 40 A rating valid at 30 °C and 40 °C (derate above that per the thermal curve). Overvoltage category III and pollution degree 2 suit fixed-installation mains distribution. The 10 000 mechanical switching cycles cover typical service life for a panel MCB. The part carries the EN 60898 rating (4.5 kA) and is designed for residential and infrastructure applications per the manufacturer's suitability listing.