What it is and what it does
The Siemens 5SY4504-7CC is a SENTRON miniature circuit breaker (MCB) with a 2-pole 1P+N configuration — one protected pole plus a switched neutral — rated 4 A at 35 °C with a C tripping characteristic. That C-curve means it holds through mild inrush (5–10× rated) but trips fast on hard shorts, so it's the go-to for general-purpose branch circuits feeding resistive and moderate inductive loads like contactor coils, small transformers, or lighting banks in a control panel. Breaking capacity is 10 kA per EN 60898 and 5 kA per UL 1077 / CSA C22.2 No.235. The 10 kA figure tells you it can safely interrupt a fault up to that level without welding contacts or cascading upstream — critical for selectivity studies in a distribution board. The UL 1077 rating means it's recognized as a supplementary protector in North American panels, not a branch-circuit OCPD, so check your local code if you're using it in a UL 508A industrial control panel.
Mounting and integration
Snaps onto DIN rail via the quick-assembly system, occupies 2 modular width units (36 mm), and can be mounted in any position. Installation depth is 70 mm; overall depth is 76 mm. The combined top and bottom terminals accept conductors up to the usual MCB range, and the unit is sealable — useful for panel builders who need to lock out adjustment after commissioning. Pollution degree 3 and overvoltage category III mean it's rated for the industrial environment inside a non-conditioned enclosure.
Thermal derating and environmental range
Rated 4 A at 35 °C, but the thermal trip element derates with ambient temperature: 3.76 A at 40 °C, 3.64 A at 45 °C, 3.5 A at 50 °C, and 3.37 A at 55 °C. If your panel runs hot — say 50 °C inside — size the load to 3.5 A continuous, not the nameplate 4 A. Operating temperature range is -40 °C to 75 °C, so it's fine for outdoor cabinets in cold climates or near ovens. Humidity tolerance is specified: max 95% RH up to 55 °C, derating to 35% RH at 75 °C.