{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-1FA31","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-1FA31","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-1FA31","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA31","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 4-pole 3 NO + 1 NC, 10 A maximum, screw terminals, snap-on for 3RT1 contactors, 51 x 44 x 38 mm, IP20 front.","salesMarkdown":"The Siemens 3RH1921-1FA31 is a SIRIUS auxiliary switch block designed to snap onto 3RT1 contactors, adding 4 poles of auxiliary contacts (3 normally open, 1 normally closed) in a compact 51 x 44 x 38 mm footprint. It is rated for a maximum thermal current of 10 A and carries switching capacities ranging from 10 A at 24 V up to 0.3 A at 220 V, with AC-15 ratings at 690 V of 1 A. The contact arrangement follows EN 50005, and the block uses screw-type terminals accepting 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) conductors. This part is a phased-out product. The manufacturer lists it as a 'Phased-out product' with the official successor being the SIRIUS 3RH2 series. For BOM lines that specify the 3RH1921-1FA31, the direct replacement path is to the newer 3RH2 family, though panel re-qualification may be needed due to dimensional differences (the 3RH2 blocks are larger at 73 x 45 x 57.5 mm vs. the 3RH1921's 51 x 44 x 38 mm). Snap-on mounting directly onto 3RT1 contactors — no tools required for attachment. The block adds 51 mm depth to the contactor assembly. Front protection is IP20, meaning it is finger-safe for panel environments but not rated for washdown. Mechanical life is rated at 10 million switching cycles typical, with contact reliability of 1 faulty switching per 100 million operations at 17 V, 1 mA. ## Switching Capacity Profile The 3RH1921-1FA31 provides two sets of switching ratings: one set for general use (maximum 10 A, with derated values at higher voltages: 6 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V) and a separate set for AC-15 duty at 690 V (1 A).","metaTitle":"Siemens 3RH1921-1FA31 SIRIUS Auxiliary Switch Block, 3NO+1NC","metaDescription":"Siemens 3RH1921-1FA31 SIRIUS attachable auxiliary switch block, 4-pole (3 NO + 1 NC), 10 A maximum, for 3RT1 contactors. Phased out; successor is 3RH2 series. Sourced to order agai","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":"3","With Core End Processing":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 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 ... 16), 2x (18 ... 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":"screw-type terminals","insulation voltage with degree of pollution 3 at AC rated value":"690 V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$149.40","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=494791&mlfb=3RH1921-1FA31","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA31/alternatives.json"},"ai":{"faq":[{"question":"What is 3RH1921-1FA31's listed note (with 3RT1) on this component line?","answer":"The note states the block is designed 'with 3RT1' — meaning it snaps onto Siemens 3RT1 contactors as an add-on auxiliary switch block."},{"question":"What is 3RH1921-1FA31's listed depth (51 mm) on this component line?","answer":"The depth is 51 mm, which is the dimension added to the contactor assembly when the block is mounted on the front."},{"question":"Will 3RH1921-1FA31 drop into a panel that was specified around 3RH2140-1BP40 without rewiring?","answer":"No. The 3RH2140-1BP40 is a different form factor (73 x 45 x 57.5 mm vs. 51 x 44 x 38 mm) and is a complete auxiliary contactor, not an attachable block. The 3RH1921-1FA31 is an add-on block for 3RT1 contactors, so the panel layout and wiring scheme would differ significantly."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-1FA31","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/3RH1921-1FA31 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}}