{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-2KA20","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-2KA20","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-2KA20","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-2KA20","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch, 3RH1921-2KA20, 2 N/O, spring-loaded terminals, snap-on for S0 contactor size, 10 A AC-12, 71 x 10 x 72.5 mm.","salesMarkdown":"The Siemens SIRIUS 3RH1921-2KA20 is a 2 N/O auxiliary switch designed to snap onto S0-size contactors and contactor relays. It uses spring-loaded terminals (cage clamp) and carries IP20 finger protection on the front — standard for panel-mounted control gear where accidental contact is a concern. The contacts are rated for 10 A at AC-12 (resistive load) and 6 A at 24 V, 2 A at 48/60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220/250 V, and 3 A at 400 V. The AC-12 rating (10 A) is the headline number for general-purpose resistive switching; the lower DC and higher-voltage AC figures reflect real arc-interruption limits. For inductive loads (AC-15, DC-13), derate accordingly — the mirror-contact compliance (IEC 60947-4-1) means this switch is suitable for feedback circuits in safety-related contactor applications when paired with a 3RT1 contactor. ## Mechanical endurance and contact reliability Rated for 10 million mechanical operating cycles typical. ## Panel integration — snap-on and wiring Snap-on mounting for S0 contactors; a second unit can be mounted laterally. Accepts 2 x (0.5…2.5 mm²) solid/stranded or 2 x (20…14 AWG) without ferrules, and 2 x (0.5…1.5 mm²) finely stranded with core-end processing. Dimensions: 71 mm deep, 10 mm wide, 72.5 mm high — the 10 mm width is the critical panel-space number when stacking multiple auxiliaries.","metaTitle":"Siemens SIRIUS 3RH1921-2KA20 Auxiliary Switch, 2 N/O, Spring","metaDescription":"Siemens SIRIUS 3RH1921-2KA20 auxiliary switch, 2 N/O contacts, spring-loaded terminals, snap-on for S0 contactors. Rated 10 A AC-12, 6 A at 24 V. Active production. Quoted to order","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Contactors"],"specifications":{"Depth":"71 mm","Width":"10 mm","title":"3RH1921-2KA20","Height":"72.5 mm","at 24 V":"6 A","at 48 V":"2 A","at 60 V":"2 A","at 110 V":"1 A","at 125 V":"0.9 A","at 220 V":"0.3 A","at 230 V":"6 A","at 250 V":"0.3 A","at 400 V":"3 A","description":"second lateral Auxiliary switch, 2 NO contacts, spring-type terminal, for contactors 3RT1","During Storage":"-55 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"snap-on mounting","Product Category":"Auxiliary switch","Size Of Contactor":"S0","Solid Or Stranded":"2x (0.5 ... 2.5 mm²)","Product Brand Name":"SIRIUS","Product Designation":"auxiliary switch","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","Design Of The Product":"second can be mounted laterally","Instantaneous Contact":"2","Substance Prohibitance (Date)":"07/01/2006","protection class IP on the front":"IP20","Surge Voltage Resistance Rated Value":"6 kV","for AWG cables for auxiliary contacts":"2x (20 ... 14)","Finely Stranded With Core End Processing":"2x (0.5 ... 1.5 mm²)","Contact Reliability Of Auxiliary Contacts":"1 faulty switching per 100 million (17 V, 1 mA)","mirror contact according to IEC 60947-4-1":"Yes; with 3RT1","Finely Stranded Without Core End Processing":"2x (0.5 ... 2.5 mm²)","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","operational current of auxiliary contacts at AC-12 maximum":"10 A","Type Of Electrical Connection For Auxiliary And Control Circuit":"spring-loaded terminals","insulation voltage with degree of pollution 3 at AC rated value":"500 V","number of CO contacts of auxiliary contacts instantaneous contact":"0","AWG number as coded connectable conductor cross section for auxiliary contacts":"20 ... 14"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/9824e128ba71247e02678bac76b2e5cd.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=248665&mlfb=3RH1921-2KA20"},"ai":{"faq":[{"question":"What is 3RH1921-2KA20's listed depth (71 mm) and width (10 mm)?","answer":"Depth is 71 mm, width is 10 mm, height is 72.5 mm. The 10 mm width is the key dimension for panel space when stacking auxiliaries on S0 contactors."},{"question":"Will 3RH1921-2KA20 drop into a panel that was specified around 3RH2122-2AV60 without rewiring?","answer":"Both are S0-size snap-on auxiliary switches, so the mechanical fit is the same. The 3RH1921-2KA20 uses spring-loaded terminals; the 3RH2122-2AV60 uses screw terminals — wiring method differs, but the footprint and contactor interface are identical."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-2KA20","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/3RH1921-2KA20 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}}