{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SY8440-7","brand":"Siemens","brandSlug":"siemens","productSlug":"5SY8440-7","canonicalUrl":"https://aoctrl.com/siemens/5SY8440-7","factsUrl":"https://aoctrl.com/api/mcp/products/5SY8440-7","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SY8440-7, 4-pole miniature circuit breaker, 40 A rated current, C tripping characteristic, 25 kA breaking capacity at 440 V AC per IEC 60947-2, 4 modular width units.","salesMarkdown":"## What it is and what it does The Siemens 5SY8440-7 is a SENTRON 4-pole miniature circuit breaker rated 40 A with a C tripping characteristic. It breaks up to 25 kA at 440 V AC per IEC 60947-2, and 15 kA at DC per the same standard. Under UL 1077 and CSA C22.2 No. 235, it's listed at 5 kA. That 25 kA interrupting rating means it can clear a bolted fault on a 400 V industrial distribution board without upstream fuses needing to open — useful for selectivity in a sub-panel feeding motor control centers or machine tools. ## Where it goes and how it fits Snaps onto a DIN rail via the quick assembly system — 4 modular width units (72 mm wide). Mounts in any position, which simplifies layout in a crowded enclosure. Installation depth is 70 mm, overall depth 76 mm. Pollution degree 3 and overvoltage category III mean it's rated for the conductive-dust and transient environment inside an industrial panel, not just a clean residential load center. ## Thermal derating — the real-world current Rated 40 A at 45 °C ambient, but drops to 39 A at 50 °C and 37.96 A at 55 °C. If this breaker sits in a non-ventilated enclosure near other heat sources, the 55 °C figure is the one that governs continuous load. The C-curve (5-10x In magnetic trip) is standard for motor branch circuits and general industrial loads where inrush isn't extreme.","metaTitle":"Siemens 5SY8440-7 SENTRON MCB, 4P, 40 A, C-Curve, 25 kA","metaDescription":"Siemens 5SY8440-7 SENTRON miniature circuit breaker, 4-pole, 40 A, C characteristic, 25 kA breaking capacity per IEC 60947-2. Active production. Sourced 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","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Degree Of Pollution":"3","Product Designation":"Miniature circuit breaker","acc. to IEC 81346-2":"F","at AC / rated value":"40 A","protection class IP":"IP20, with connected conductors","Overvoltage Category":"III","Combined Terminal Top":"Yes","acc. to DIN EN 61346-2":"F","at 45 °C / rated value":"40 A","at 50 °C / rated value":"39 A","at 55 °C / rated value":"37.96 A","Combined Terminal Bottom":"Yes","Suitability For Operation":"Mechanical engineering / industry","Number Of Modular Width Units":"4","Tripping Characteristic Class":"C","Position / Of Power Supply Cord":"Any","acc. to IEC 60947-2 / rated value":"25 kA","Product Feature / Touch Protection":"Yes","Influence Of The Surrounding Temperature":"max. 95% to 55°C, max. 55% to 70°C, max. 35% to 75°C","at DC / acc. to IEC 60947-2 / rated value":"15 kA","Type Of Voltage / Of The Operating Voltage":"AC","at AC / acc. to UL 1077 and CSA C22.2 No.235":"5 kA","vibration resistance / acc. to IEC 60068-2-6":"±1mm at 5 to 25Hz; 50m/s² at 25 to 150Hz","Product Component / Neutral Conductor Switching":"No","with multi-phase operation / at AC / rated value":"440 V","operating voltage / at DC / rated value / maximum":"72 V","with single-phase operation / at AC / rated value":"440 V","Mechanical Service Life (Switching Cycles) / Typical":"10 000"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/1a8e5ab59ba3e5b19ca3b0055ef98323.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=68128&mlfb=5SY8440-7","alternativesUrl":"https://aoctrl.com/api/mcp/products/5SY8440-7/alternatives.json"},"ai":{"faq":[{"question":"What is the breaking capacity of 5SY8440-7?","answer":"25 kA at 440 V AC per IEC 60947-2, 15 kA at DC per the same standard, and 5 kA under UL 1077 / CSA C22.2 No. 235."},{"question":"Will 5SY8440-7 drop into a panel built for 5SY6332-7CC without rewiring?","answer":"Both are 4-pole SENTRON MCBs on the same DIN-rail footprint, so the mechanical fit is identical. The 5SY8440-7 is a 40 A C-curve; the 5SY6332-7CC is a 32 A C-curve. If the circuit is sized for 40 A, the 5SY8440-7 is a direct drop-in. If the panel was wired for 32 A, verify the conductor and upstream protection are rated for 40 A before swapping."},{"question":"Where can I buy 5SY8440-7?","answer":"Sourced and quoted to order against an RFQ through independent distribution channels. Availability and current pricing are confirmed at quote time."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SY8440-7","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/5SY8440-7 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}}