Siemens 5SY7114-8 — SENTRON D-curve MCB, 0.3 A
The Siemens 5SY7114-8 is a SENTRON miniature circuit breaker, 1-pole, with a D tripping characteristic rated at 0.3 A. This is a current-production part, not a phase-out or NRND line item — the lifecycle stage is listed as current, so it's still a standard catalog offering from Siemens. Tripping characteristic class D. At 0.3 A, this is a control-circuit or instrumentation feeder. Breaking capacity is the headline: 15 kA per EN 60898 for household-type installations, and 50 kA per IEC 60947-2 for industrial panel duty. At DC per IEC 60947-2 it still holds 15 kA. That 50 kA figure at 400 V AC means it can safely interrupt a fault up to 50 kA without welding contacts or cascading upstream — a serious SCCR rating for a 1-MWU breaker.
Fit, mounting, and panel integration
Snap-on DIN rail mount, 18 mm width (1 modular width unit), 76 mm depth, 90 mm height. Installation depth is 70 mm. Mounting position is any — horizontal, vertical, upside down, doesn't matter for the thermal-magnetic trip. The quick assembly system (fastening method) means it clips onto the rail and engages the busbar without tools. Combined terminal top and bottom — both line and load sides accept the same conductor range. IP20 with connected conductors, so it's for enclosed panels only, not open washdown areas. Overvoltage category III and degree of pollution 3 confirm it's rated for fixed installations inside a distribution board or control cabinet. Touch protection is built in (product feature), and the breaker is sealable — useful for installations where the utility or inspector needs to lock the toggle position.
Thermal derating and ambient limits
The 0.3 A rating holds at 35 °C. At 45 °C it derates to 0.27 A, at 50 °C to 0.26 A, at 55 °C to 0.25 A, and at 60 °C to 0.24 A. If your panel ambient runs hot, factor that in — the breaker won't trip on overload at the full 0.3 A above 35 °C. Operating range is -40 °C to 75 °C, with humidity limits: 95% up to 55 °C, 55% up to 70 °C, 35% up to 75 °C.
Sourcing and lifecycle
Current production. Standard catalog SKU in the SENTRON 5SY series. Sourced and quoted to order against an RFQ through independent distribution.