{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SY8440-8BB08","brand":"Siemens","brandSlug":"siemens","productSlug":"5SY8440-8BB08","canonicalUrl":"https://aoctrl.com/siemens/5SY8440-8BB08","factsUrl":"https://aoctrl.com/api/mcp/products/5SY8440-8BB08","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SY8440-8BB08, 4-pole miniature circuit breaker, D tripping characteristic, 25 kA breaking capacity at 400 V AC per IEC 60947-2, 72 mm wide, 76 mm deep, 90 mm tall.","salesMarkdown":"The Siemens 5SY8440-8BB08 is a 4-pole miniature circuit breaker from the SENTRON family, designed with a D tripping characteristic and a magnetic-only trip mechanism. It's rated for 400 V AC at 50/60 Hz with a breaking capacity of 25 kA per IEC 60947-2, and 5 kA per UL 1077 and CSA C22.2 No. 235. The D curve means it's built for loads with high inrush currents — think motor circuits, transformers, or welding equipment — where the short magnetic trip delay prevents nuisance tripping on startup. ## Mounting and integration Snaps onto DIN rail via the quick assembly system and occupies 4 modular width units (72 mm total width). Mounting position is any orientation, which helps when you're packing a tight panel. Installation depth is 70 mm; the overall depth including terminals is 76 mm. Combined terminals at top and bottom accept supply from either direction — no need to flip the breaker for top-feed vs bottom-feed. ## Environmental and compliance Rated for pollution degree 3 and overvoltage category III, which covers industrial environments where transient overvoltages are common. Ambient temperature range spans -40 °C to 75 °C, with derating for humidity: max 95% RH up to 55 °C, then dropping to 35% at 75 °C. The housing is halogen-free and silicon-free — a plus for clean-room or food-grade installations where outgassing matters. Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz. Mechanical service life is 10,000 operating cycles typical. ## Key ratings and what they mean The 25 kA breaking capacity at 400 V AC per IEC 60947-2 means this breaker can safely interrupt fault currents up to that level without welding contacts or causing arc flash damage downstream. The UL 1077 supplementary protector rating of 5 kA covers North American installations where it's used as a branch-circuit protector. Power loss per pole is 3 W at rated current in hot operating state — factor that into panel thermal calculations if you're packing multiple breakers side by side. The magnetic-only trip (no thermal bimetal) makes it suitable for short-circuit protection only; overload protection must be provided upstream or by a separate device.","metaTitle":"Siemens 5SY8440-8BB08 SENTRON MCB, 4P, D Curve, 25 kA IEC","metaDescription":"Siemens SENTRON 5SY8440-8BB08 miniature circuit breaker, 4-pole, D tripping characteristic, 25 kA breaking capacity per IEC 60947-2. Current production. Available to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Miniature Circuit Breakers (MCB)"],"specifications":{"Depth":"76 mm","Width":"72 mm","Height":"90 mm","Maximum":"75 °C","Minimum":"-40 °C","Sealable":"Yes","Halogen-Free":"Yes","Silicon-Free":"Yes","Design Of Pole":"4P","Number Of Poles":"4","lifecycle_stage":"current","Fastening Method":"Quick assembly system","Mounting Position":"any","at AC rated value":"400 V","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Degree Of Pollution":"3","Product Designation":"Miniature circuit breaker","protection class IP":"IP20, with connected conductors","Overvoltage Category":"III","Combined Terminal Top":"Yes","Design Of The Product":"Only magnetic tripping operation","Combined Terminal Bottom":"Yes","Suitability For Operation":"Mechanical engineering / industry","Neutral Conductor Switching":"No","Number Of Modular Width Units":"4","Position Of Power Supply Cord":"Any","Tripping Characteristic Class":"D","according to IEC 60947-2 rated value":"25 kA","Influence Of The Surrounding Temperature":"max. 95% to 55°C, max. 55% to 70°C, max. 35% to 75°C","Type Of Voltage Of The Operating Voltage":"AC","Value Range Of The Supply Voltage Frequency":"50/60 Hz","operating voltage at DC rated value maximum":"72 V","with multi-phase operation at AC rated value":"440 V","with single-phase operation at AC rated value":"440 V","at AC according to UL 1077 and CSA C22.2 No.235":"5 kA","vibration resistance according to IEC 60068-2-6":"±1mm at 5 to 25Hz; 50m/s² at 25 to 150Hz","Mechanical Service Life (Operating Cycles) Typical":"10 000","Product Extension Installable Supplementary Devices":"Yes","power loss [W] for rated value of the current at AC in hot operating state per pole":"3 W"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/11b16e15dbdb7a1a663ee3b6b8081b69.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=63723&mlfb=5SY8440-8BB08","alternativesUrl":"https://aoctrl.com/api/mcp/products/5SY8440-8BB08/alternatives.json"},"ai":{"faq":[],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SY8440-8BB08","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/5SY8440-8BB08 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-09-02T08:15:54.622Z","lastPublished":"2026-09-02T08:15:54.622Z","indexable":true}}