{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SU1874-8BK81","brand":"Siemens","brandSlug":"siemens","productSlug":"5SU1874-8BK81","canonicalUrl":"https://aoctrl.com/siemens/5SU1874-8BK81","factsUrl":"https://aoctrl.com/api/mcp/products/5SU1874-8BK81","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SU1 series, RCBO, 4-pole, 100 A rated current, Type B fault current, D tripping characteristic, 10 kA breaking capacity, selective design.","salesMarkdown":"The Siemens 5SU1874-8BK81 is a 4-pole RCBO from the SENTRON 5SU1 series, combining overcurrent protection (MCB function) with residual current protection (RCD function) in a single DIN-rail mounted unit. The D tripping characteristic (10–20× In magnetic trip) suits loads with high inrush, like motors, transformers, or welding equipment. ## Selective design — what that means for coordination This RCBO is explicitly a selective (Type S) device per the product design. That means it has a deliberate short time delay before tripping on residual current, allowing downstream RCDs to clear a fault first. In a panel with multiple sub-circuits, you can place this as the main incomer RCBO and feed standard (non-delayed) RCDs or RCBOs downstream — the selective unit lets the branch device trip without taking the whole board down. The 100 A rating and 4-pole configuration make it a natural fit for a main switch or feeder position in a three-phase distribution board. At 40 °C it derates to 92.5 A, at 45 °C to 89 A, at 50 °C to 85 A, at 55 °C to 81 A, and at 60 °C to 77 A. If the panel internal temperature runs hot — common in densely packed enclosures or near heat sources — size the upstream conductor and load accordingly. The device is rated for any mounting position, which gives flexibility in tight cabinets, but the thermal derating curve is the binding constraint. The unit occupies 11 width units (198 mm) on a DIN rail, with a depth of 77 mm and an installation depth of 70 mm (the extra 7 mm accounts for the housing overhang). Height is 90 mm. Supply can enter from either the top or bottom, which simplifies busbar and cable routing in retrofit panels. It is halogen-free and silicon-free, meeting clean-room and fire-safety requirements in data centers or critical infrastructure.","metaTitle":"Siemens 5SU1874-8BK81 SENTRON RCBO, 100 A, Type B, 10 kA","metaDescription":"Siemens SENTRON 5SU1874-8BK81 RCBO, 4-pole, 100 A rated, Type B fault current, 10 kA breaking capacity. Selective design, D characteristic. Active production, sourced to order. Req","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Residual Current Breakers (RCCB/RCBO)"],"specifications":{"Depth":"77 mm","Width":"198 mm","Height":"90 mm","Maximum":"75 °C","Minimum":"-40 °C","at 30 Cel":"100 A","at 40 Cel":"92.5 A","at 45 Cel":"89 A","at 50 Cel":"85 A","at 55 Cel":"81 A","at 60 Cel":"77 A","Halogen-Free":"Yes","Silicon-Free":"Yes","Number of poles":"4","Type of voltage":"AC","lifecycle_stage":"current","Mounting position":"any","Installation depth":"70 mm","Product brand name":"SENTRON","Degree of pollution":"2","Operating frequency":"50/60 Hz","Product designation":"RCBO","Protection class IP":"IP20, if the distribution board is installed, with connected conductors","at AC / rated value":"230/400 V","Overvoltage category":"III","Design of the product":"selective","Energy limiting class":"3","Number of width units":"11","Type of fault current":"B","Number of poles / Note":"4P","acc. to DIN EN 61346-2":"F","acc. to DIN EN 81346-2":"F","circuit-breaker / Design":"5SU1","Current / at AC / rated value":"100 A","Tripping characteristic class":"D","acc. to EN 60898 / rated value":"10 kA","For Testing Equipment / Minimum":"100 V","Position / of power supply cord":"Either top or bottom","Number of poles / with protection":"4","acc. to IEC 60947-2 / rated value":"10 kA","Product feature / Touch protection":"Yes","Supply voltage frequency / rated value":"50 Hz","Tripping residual current / rated value":"1 000 mA","Influence of the surrounding temperature":"Max. 95% humidity","Surge current resistance / at (8/20) μs":"5 kA","Product function / neutral conductor switching":"Yes","Mechanical service life (switching cycles) / typical":"10 000"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=396156&mlfb=5SU1874-8BK81","alternativesUrl":"https://aoctrl.com/api/mcp/products/5SU1874-8BK81/alternatives.json"},"ai":{"faq":[{"question":"Where can I buy 5SU1874-8BK81 and get a price?","answer":"This RCBO is sourced to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time — submit a request for a firm price and lead time."},{"question":"What is the closest functional alternative to 5SU1874-8BK81?","answer":"The 5SL4363-7 is a Siemens RCBO in the same SENTRON family, but it is a standard (non-selective) Type A device with a lower current rating. The 5SU1874-8BK81 is selective (Type S), Type B, and rated 100 A — if your application requires delayed tripping on residual current and DC fault detection, the 5SU1874-8BK81 is the correct choice."},{"question":"What compliance documentation does Siemens provide for 5SU1874-8BK81?","answer":"The device is designed to EN 60898 and IEC 60947-2, with a 10 kA breaking capacity under both standards. It carries pollution degree 2 and overvoltage category III ratings. The SENTRON series generally supports RoHS and REACH compliance; specific declarations are available from Siemens documentation."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SU1874-8BK81","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/5SU1874-8BK81 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}}