{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SM2121-0","brand":"Siemens","brandSlug":"siemens","productSlug":"5SM2121-0","canonicalUrl":"https://aoctrl.com/siemens/5SM2121-0","factsUrl":"https://aoctrl.com/api/mcp/products/5SM2121-0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SM2121-0 RC unit for 5SY miniature circuit breaker, 2-pole, type AC, rated fault current 10 mA, rated current 16 A, rated voltage AC 230 V.","salesMarkdown":"The Siemens SENTRON 5SM2121-0 is a residual-current device (RCD) unit designed as a plug-in accessory for the 5SY series miniature circuit breakers. It provides earth leakage protection for single-phase AC circuits at 230 V, rated 16 A with a 10 mA trip sensitivity — a high-sensitivity threshold suited for protecting individual circuits against fault currents that could otherwise go undetected by a standard MCB. As an instantaneous (type AC) device, it responds to sinusoidal AC residual currents without intentional delay, which means it clears ground faults as they occur but does not discriminate against nuisance tripping from transient surges on the line. It clips directly onto the right-hand side of a compatible 5SY MCB — the fastening method is REG (rear-edge guide), so the combination forms a single 2-pole assembly that shares the busbar connection. The IP20 rating applies once the distribution board is installed with conductors connected; the assembly is not sealable, so it remains accessible for periodic testing via the built-in test circuit (minimum supply voltage 195 V for the test equipment).","metaTitle":"Siemens 5SM2121-0 SENTRON RCD Unit, 16 A, 10 mA, 2-pole","metaDescription":"Siemens SENTRON 5SM2121-0 RC unit for 5SY MCB, 2-pole, type AC, 16 A, 10 mA, 230 V. Current lifecycle stage. IP20. Available to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Residual Current Breakers (RCCB/RCBO)"],"specifications":{"title":"5SM2121-0","Maximum":"45 °C","Minimum":"-5 °C","Sealable":"No","description":"RC unit for 5SY, 2-pole, type AC, In: 16 A, 10 mA, Un AC: 230 V","Number Of Poles":"2","lifecycle_stage":"current","Fastening Method":"REG","Mounting Position":"any","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Degree Of Pollution":"2","Maximum Permissible":"75 °C","Minimum Permissible":"-40 °C","Product Designation":"RCD-unit","protection class IP":"IP20, if the distribution board is installed, with connected conductors","Overvoltage Category":"III","Design Of The Product":"instantaneous","OFF-delay time adjustable":"No","Number Of Modular Width Units":"2","Rated Fault Current Adjustable":"No","Protection Function False Tripping":"Yes","insulation voltage (Ui) rated value":"460 V","Surge Voltage Resistance Rated Value":"4 000 V","Value Range Of The Operating Frequency":"50 Hz","Value Range Of The Supply Voltage Frequency":"50 Hz","Supply Voltage For Testing Equipment Minimum":"195 V","Mechanical Service Life (Operating Cycles) Typical":"10 000","for rated value of the current at AC in hot operating state per pole":"2.5 W"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/259bc658cf15b7b428514a2030ef251e.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=489878&mlfb=5SM2121-0"},"ai":{"faq":[{"question":"What is the 5SM2121-0's operating temperature range?","answer":"The operating ambient temperature range is -5 °C to 45 °C, with storage from -40 °C to 75 °C."},{"question":"Will 5SM2121-0 drop into a panel specified around 5SL4363-7 without rewiring?","answer":"No direct physical or functional drop-in — the 5SM2121-0 is a 2-pole RCD accessory for a 5SY MCB, while 5SL4363-7 is a 3-pole standalone MCB. The 5SM2121-0 occupies 2 MW at 70 mm depth; the 5SL4363-7 occupies 3 MW at 76 mm depth. Panel layout and wiring would need adjustment."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SM2121-0","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/5SM2121-0 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}