What the ratings mean for fit
The Siemens SENTRON 5SY6040-6 is a 1P+N miniature circuit breaker with a B tripping characteristic, rated 40 A at 30 °C and 230 V AC, with a 6 kA breaking capacity per EN 60898. That B-curve means it trips between 3× and 5× rated current — designed for resistive and light inductive loads like lighting circuits, small heaters, and control transformers in residential and infrastructure panels. The 6 kA interrupting rating is the maximum fault current it can safely clear at 230 V; for most domestic and light commercial distribution boards this is sufficient, but verify your prospective short-circuit current at the installation point. The 1P+N pole design switches both line and neutral, with the neutral pole switching but not protected — common in single-phase final circuits where neutral isolation is required. At elevated ambient temperatures the breaker derates: 38 A at 40 °C, 37.2 A at 45 °C. That matters when the MCB sits in a crowded enclosure with other heat sources — the 40 A rating is only valid at 30 °C ambient. If your panel runs at 40 °C, the continuous load should not exceed 38 A.
Panel integration and mounting
The 5SY6040-6 snaps onto standard DIN rail (EN 60715) and occupies one modular width unit (18 mm). Mounting position is any — vertical, horizontal, or flat — which simplifies layout in tight enclosures. Installation depth is 70 mm; total depth including the breaker body is 76 mm. The IP20 rating (with connected conductors) means it is protected against finger contact but not water ingress — standard for indoor distribution boards. Touch protection is built in, so accidental contact with live terminals during maintenance is prevented.
Compliance and environmental
The breaker is halogen-free and silicon-free, which matters for clean-room or sensitive electronics environments where outgassing can cause contact corrosion or optical haze. It is sealable (can be locked in the OFF position for lockout/tagout). Vibration resistance per IEC 60068-2-6 is confirmed, so it holds up in transport or near rotating machinery. Pollution degree 2 and overvoltage category III suit fixed installations in residential and commercial buildings.