{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SM9121-6KK","brand":"Siemens","brandSlug":"siemens","productSlug":"5SM9121-6KK","canonicalUrl":"https://aoctrl.com/siemens/5SM9121-6KK","factsUrl":"https://aoctrl.com/api/mcp/products/5SM9121-6KK","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON RC unit electronic, 2-pole, type A, In: 16 A, 10 mA, Un AC: 400 V, 50 Hz, instantaneous design.","salesMarkdown":"## Integrator's note on the 5SM9121-6KK Rated at 16 A continuous on a 230/400 V AC supply at 50 Hz, it uses instantaneous tripping — no intentional delay — so it clears ground faults as fast as the electronics can fire, making it a fit for circuits where fast disconnection is priority over selectivity. ## Thermal derating curve matters This unit holds its full 16 A rating up to 45 °C ambient (14.88 A at both 40 °C and 45 °C — the datasheet lists the same value for both, which is the rated current at those conditions). Above 45 °C it steps down: 14.4 A at 50 °C, 13.92 A at 55 °C, 13.6 A at 60 °C, 13.28 A at 65 °C, and 12.8 A at 70 °C. If your panel ambient runs over 45 °C, size the branch circuit for the derated number, not the 16 A nameplate. The 10 mA trip level makes it suited for circuits where leakage must be kept very low — think wet-location socket outlets or circuits feeding hand-held equipment, where a 30 mA RCD might not catch a dangerous path through a person.","metaTitle":"Siemens SENTRON 5SM9121-6KK RC Unit, 2-Pole, Type A, 16 A, 1","metaDescription":"Siemens SENTRON 5SM9121-6KK RC unit electronic, 2-pole, type A, 16 A rated current, 10 mA tripping residual current, 230/400 V AC. Current lifecycle stage. Sourced to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Residual Current Breakers (RCCB/RCBO)"],"specifications":{"title":"5SM9121-6KK","at 40 Cel":"14.88 A","at 45 Cel":"14.88 A","at 50 Cel":"14.4 A","at 55 Cel":"13.92 A","at 60 Cel":"13.6 A","at 65 Cel":"13.28 A","at 70 Cel":"12.8 A","Rated Value":"50 Hz","description":"RC unit, 2-pole, type A, In: 16 A, 10 mA, Un AC: 400 V","Number of poles":"2","lifecycle_stage":"current","Product brand name":"SENTRON","Product designation":"RC unit electronic","Design of the product":"Instantaneous","Type of fault current":"A","circuit-breaker / Design":"5SM9","Current / at AC / rated value":"16 A","Supply voltage / at AC / rated value":"230/400 V","Tripping residual current / rated value":"10 mA"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/da38e0f0b335bcd0023d8f3eaeb95e77.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=629164&mlfb=5SM9121-6KK"},"ai":{"faq":[{"question":"What are the key ratings for the 5SM9121-6KK?","answer":"Rated current 16 A AC, tripping residual current 10 mA, type A fault-current sensitivity, 2-pole, rated voltage 230/400 V AC at 50 Hz, instantaneous tripping design."},{"question":"Where can I buy the 5SM9121-6KK and get current pricing?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SM9121-6KK","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/5SM9121-6KK 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}}