{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-2FA04","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-2FA04","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-2FA04","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-2FA04","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 4 NC, spring-loaded terminals, 10 A max, snap-on mounting, 51 mm depth.","salesMarkdown":"## Auxiliary switch block for SIRIUS contactor relays and power contactors The Siemens SIRIUS 3RH1921-2FA04 is a 4 NC auxiliary switch block designed for use with SIRIUS contactor relays and power contactors. It snaps onto the front of the contactor via the snap-on mounting method, adding four normally-closed auxiliary contacts to the switching assembly. Rated for a maximum of 10 A, with specific current ratings across multiple voltage levels: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, 6 A at 250 V, 3 A at 400 V, and 0.3 A at 220 V. For AC-15 duty at 690 V, the rated value is 1 A. The block uses spring-loaded terminals for the auxiliary and control circuit connections, accepting 2x (0.5... 1.5 mm²) with core end processing or 2x (0.5... 2.5 mm²) without. Mechanical service life is typical 10,000,000 switching cycles. ## Lifecycle and replacement The 3RH1921-2FA04 is a phased-out product. The official successor is the SIRIUS 3RH2 series auxiliary switch block. If you are replacing an existing 3RH1921-2FA04 in a panel, the 3RH2 block is the direct functional replacement, but verify terminal layout and mounting compatibility with your specific contactor frame (S0...S12).","metaTitle":"Siemens 3RH1921-2FA04 Auxiliary Switch Block, 4 NC, 10 A, Sp","metaDescription":"Siemens SIRIUS 3RH1921-2FA04 auxiliary switch block, 4 NC, 10 A max, spring terminals. Phased-out; successor 3RH2. Sourced to order. Request quote.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Contactors"],"specifications":{"Note":"with 3RT1","Depth":"51 mm","Width":"44 mm","Height":"38 mm","Maximum":"10 A","at 24 V":"6 A","at 60 V":"2 A","at 110 V":"1 A","at 125 V":"6 A","at 220 V":"0.3 A","at 230 V":"6 A","at 250 V":"6 A","at 400 V":"3 A","During Storage":"-55 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"snap-on mounting","Product Brand Name":"SIRIUS","Suitability For Use":"Contactor relay and power contactor","at 24 V rated value":"10 A","at 60 V rated value":"4.7 A","at 110 V rated value":"3 A","at 220 V rated value":"1.2 A","at 440 V rated value":"0.5 A","at 600 V rated value":"0.26 A","Instantaneous Contact":"0","With Core End Processing":"2x (0.5 ... 1.5 mm²)","Without Core End Processing":"2x (0.5 ... 2.5 mm²)","at AC-15 at 690 V rated value":"1 A","protection class IP on the front":"IP20","Surge Voltage Resistance Rated Value":"6 kV","at AWG cables for auxiliary contacts":"2x (20 ... 14)","Contact Reliability Of Auxiliary Contacts":"1 faulty switching per 100 million (17 V, 1 mA)","Mechanical Service Life (Switching Cycles) Typical":"10 000 000","Type Of Electrical Connection For Auxiliary And Control Circuit":"spring-loaded terminals","insulation voltage with degree of pollution 3 at AC rated value":"690 V"}},"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=197757&mlfb=3RH1921-2FA04","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-2FA04/alternatives.json"},"ai":{"faq":[{"question":"What is 3RH1921-2FA04's listed note (with 3RT1) on this component line?","answer":"The note indicates the auxiliary switch block is designed for use with 3RT1 contactors and contactor relays."},{"question":"What is 3RH1921-2FA04's listed depth (51 mm) on this component line?","answer":"The depth of the 3RH1921-2FA04 is 51 mm. Overall dimensions are 51 mm depth, 44 mm width, and 38 mm height."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-2FA04","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/3RH1921-2FA04 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}}