{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-1LA20","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-1LA20","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-1LA20","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1LA20","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 2 NC contacts, screw terminals, 10 A rated, snap-on for 3RT1 contactors.","salesMarkdown":"It occupies the 44 mm width slot on the contactor's front face and adds 51 mm depth to the assembly. The IP20 rated front means it's intended for enclosed panel use only — no exposed live parts in a dead-front cabinet. ## Switching Capability Across the Voltage Range Rated for a maximum of 10 A, the block's actual interrupting capacity depends on the circuit voltage. At 24 V it handles 6 A (AC-15/DC-13 typical), rising to 6 A at 125 V, 230 V, and 250 V. At 400 V it still manages 3 A. The ratings drop at higher voltages: 0.3 A at 220 V and 0.5 A at 440 V. For control circuits at 24 VDC, the continuous rated current is 10 A. These are the numbers that govern whether this block can interrupt your specific pilot-duty load without welding contacts. ## Lifecycle Reality This is a phased-out product. The official successor is the SIRIUS 3RH2 series. If you are maintaining an existing panel with a 3RT1 contactor and need a drop-in replacement, the 3RH1921-1LA20 is the correct form, fit, and function. For new designs, the 3RH2 block is the current-production path. Rated for 10 million mechanical operating cycles typical, with contact reliability of 1 faulty switching per 100 million operations at 17 V, 1 mA. The block withstands a surge voltage of 6 kV and is rated for an insulation voltage of 690 V at pollution degree 3. Wire termination accepts 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core end processing, or 2x (20 to 16) or 2x (18 to 14) AWG.","metaTitle":"Siemens 3RH1921-1LA20 Auxiliary Switch Block, 2 NC, 10 A","metaDescription":"Siemens SIRIUS 3RH1921-1LA20 auxiliary switch block with 2 NC contacts, rated 10 A. Snap-on mounting for 3RT1 contactors. Sourced to order via RFQ.","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":"2","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 (Operating 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":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=380804&mlfb=3RH1921-1LA20","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1LA20/alternatives.json"},"ai":{"faq":[{"question":"What does the note 'with 3RT1' mean?","answer":"It means this auxiliary switch block is specifically designed to snap onto the front of a Siemens SIRIUS 3RT1 series power contactor. It is not a standalone device; it mounts to the contactor's front face to add normally-closed auxiliary contacts."},{"question":"What is the depth of this block?","answer":"51 mm. This is the dimension added to the contactor's overall depth when the block is mounted on the front."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-1LA20","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/3RH1921-1LA20 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}}