{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SM3745-8","brand":"Siemens","brandSlug":"siemens","productSlug":"5SM3745-8","canonicalUrl":"https://aoctrl.com/siemens/5SM3745-8","factsUrl":"https://aoctrl.com/api/mcp/products/5SM3745-8","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON selective RCCB, 4-pole, 125 A rated, 500 mA residual current, Type A, 400 V AC, 50 Hz, IP20, DIN rail mount.","salesMarkdown":"The Siemens SENTRON 5SM3745-8 is a selective (time-delayed) residual current circuit breaker (RCCB) — 4-pole, rated 125 A at 400 V AC, 50 Hz, with a 500 mA residual trip threshold, Type A. Selective means it delays tripping to coordinate with downstream RCCBs, so a fault on a branch doesn't take out the whole submain. That 500 mA threshold is higher than the standard 30 mA or 300 mA, deliberately — it's sized for the main incomer or a feeder where nuisance tripping from leakage on multiple circuits needs to be avoided. ## Breaking capacity and standards compliance Short-circuit withstand is 10 kA per IEC 61008-1 (1.25 kA per EN 60898). The 1.25 kA figure under EN 60898 is the conditional rating for the RCCB when backed by an upstream MCB or fuse; the 10 kA under IEC 61008-1 is the unconditional rating for the RCCB alone. Either way, if your panel's fault current exceeds 10 kA, you need a current-limiting device ahead of it. ## Temperature derating — the real usable current Above that, derating kicks in: 120 A at 50 °C, 115 A at 55 °C, 110 A at 60 °C, 105 A at 65 °C, and 100 A at 70 °C. The permissible I²t is 94 000 A²·s; let-through current is 8 000 A — both figures matter for coordination with the downstream MCB. Snap-on DIN rail (REG) mount, any orientation. That 77 mm depth means it needs clearance behind the DIN rail — standard 80 mm deep enclosures are tight; 100 mm or deeper is safer. IP20 with conductors connected — fine inside a distribution board, not for wet or dusty locations. Silicon-free construction, so it won't outgas contaminants in sensitive environments.","metaTitle":"Siemens SENTRON 5SM3745-8 RCCB, 4P, 125A, 500mA, Type A Sele","metaDescription":"Siemens SENTRON 5SM3745-8 selective RCCB, 4-pole, 125 A, 500 mA residual, Type A, 10 kA SCCR, 400 V AC, 50 Hz. Current production. Sourced to order. Request a quote.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Residual Current Breakers (RCCB/RCBO)"],"specifications":{"Depth":"77 mm","Width":"72 mm","Height":"90 mm","Maximum":"45 °C","Minimum":"-25 °C","Number Of Poles":"4","lifecycle_stage":"current","Fastening Method":"DIN rail (REG)","Mounting Position":"any","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Maximum Permissible":"75 °C","Minimum Permissible":"-40 °C","Product Designation":"RCCB","at AC / rated value":"125 A","protection class IP":"IP20, if the distribution board is installed, with connected conductors","Overvoltage Category":"III","Design Of The Product":"Selective","Residual Current Type":"A","I2t value / permissible":"94 000 A²·s","at 40 °C / rated value":"125 A","at 45 °C / rated value":"125 A","at 50 °C / rated value":"120 A","at 55 °C / rated value":"115 A","at 60 °C / rated value":"110 A","at 65 °C / rated value":"105 A","at 70 °C / rated value":"100 A","Short-Circuit Current Rating":"10 kA","Number Of Modular Width Units":"4","Product Feature / Silicon-Free":"Yes","Position / Of Power Supply Cord":"top or bottom","Let-Through Current / Permissible":"8 000 A","according to EN 60898 / rated value":"1.25 kA","Tripping Fault Current / Rated Value":"500 mA","Surge Current Resistance / Rated Value":"5 kA","according to IEC 61008-1 / rated value":"1.25 kA","Switching Function / Short-Term Delayed":"No","Value Range / Of The Operating Frequency":"50 Hz","value range / of the supply voltage / at AC":"400 V","Value Range / Of The Supply Voltage Frequency":"50 Hz","Supply Voltage / For Testing Equipment / Minimum":"100 V","Mechanical Service Life (Switching Cycles) / Typical":"10 000"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$1,361.44","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=349649&mlfb=5SM3745-8","alternativesUrl":"https://aoctrl.com/api/mcp/products/5SM3745-8/alternatives.json"},"ai":{"faq":[{"question":"Where can I buy 5SM3745-8?","answer":"Sourced and quoted to order through independent distribution. Submit an RFQ; availability and current pricing are confirmed at quote time."},{"question":"What does the 'selective' designation mean on this RCCB?","answer":"Selective (time-delayed) means the device delays tripping to allow downstream RCCBs to clear a fault first. This prevents a single branch fault from blacking out the entire distribution board."},{"question":"Will 5SM3745-8 drop into a panel specified for 5SL4363-7?","answer":"No — 5SL4363-7 is a miniature circuit breaker (MCB), not an RCCB. They serve different functions. The 5SM3745-8 is a 4-pole RCCB; the 5SL4363-7 is a 3-pole MCB. Panel layout and wiring differ."},{"question":"What is the depth of 5SM3745-8?","answer":"77 mm overall depth, with 70 mm installation depth behind the DIN rail."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SM3745-8","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/5SM3745-8 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}}