{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-2FA40","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-2FA40","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-2FA40","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-2FA40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 3RH1921-2FA40, 4 NC, spring-loaded terminals, for contactor relays and motor contactors sizes S0 to S12.","salesMarkdown":"It snaps onto contactor relays and power contactors in the S0 through S12 frame sizes — the \"with 3RT1\" note on the listing means it's designed to mount directly on a 3RT1-series contactor, extending its auxiliary contact capacity without additional wiring space. Contact ratings are given for both DC and AC-15 inductive loads — two different curves that govern where this block can be used. For DC switching: 10 A at 24 V, 6 A at 125 V and 230 V, 3 A at 400 V, and down to 0.3 A at 220 V. The AC-15 ratings (for solenoid and contactor coils) are 10 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. At 690 V AC-15 it's rated 1 A. These numbers define the maximum switched current at each voltage; the 690 V rating means it can handle control circuits on 690 V line supplies common in heavy industrial installations. ## Integration notes Snap-on mounting onto the contactor body — no DIN rail required, no screws. Dimensions are 44 mm wide, 51 mm deep, 38 mm high, so it adds minimal depth to the contactor stack. Spring-loaded terminals accept 2x (0.5 to 1.5 mm²) with ferrules or 2x (0.5 to 2.5 mm²) without; AWG equivalent is 2x (20 to 14). Front IP20 means finger-safe when installed in an enclosure.","metaTitle":"Siemens 3RH1921-2FA40 Auxiliary Switch Block, 4 NC, Spring T","metaDescription":"Siemens SIRIUS 3RH1921-2FA40 auxiliary switch block, 4 NC contacts, spring-loaded terminals. Phased-out; successor is 3RH2 series. 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":"4","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=231614&mlfb=3RH1921-2FA40","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-2FA40/alternatives.json"},"ai":{"faq":[{"question":"Where can I buy 3RH1921-2FA40 and how do I get a price?","answer":"This part is sourced to order through independent distribution. Submit an RFQ — availability and current pricing are confirmed at quote time."},{"question":"What is the closest functional second-source to 3RH1921-2FA40?","answer":"The official successor is the SIRIUS 3RH2 series. For a direct functional match, the 3RH2131-2AK60 is a 3 NO + 1 NC auxiliary contactor in size S00 with spring terminals, but it's a different frame size and contact arrangement — verify fit before substituting."},{"question":"What does the \"with 3RT1\" note mean?","answer":"It means this auxiliary switch block is designed to mount directly on a 3RT1-series contactor relay or power contactor, extending its auxiliary contact capacity."},{"question":"What is the depth of 3RH1921-2FA40?","answer":"51 mm."},{"question":"Will 3RH1921-2FA40 drop into a panel specified around 3RH2131-2AK60 without rewiring?","answer":"Not directly. The 3RH2131-2AK60 is a size S00 auxiliary contactor with screw and snap-on mounting, while the 3RH1921-2FA40 is a snap-on auxiliary switch block for S0–S12 contactors. They have different footprints and mounting methods."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-2FA40","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/3RH1921-2FA40 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}}