{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-1FA40","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-1FA40","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-1FA40","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 4-pole 4 NO, screw terminals, snap-on mounting, 10 A maximum, 51 mm depth.","salesMarkdown":"The Siemens 3RH1921-1FA40 is a 4-pole auxiliary switch block from the SIRIUS family, designed to snap onto a 3RT1 contactor or contactor relay. It adds four normally-open (4 NO) instantaneous contacts for signaling or interlocking in a motor control panel. The screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, so it wires up with standard ferrule sizes. The block carries a maximum thermal current of 10 A. The voltage-specific ratings tell you the switching capability at different control voltages: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, 3 A at 400 V, and 0.3 A at 220 V. For DC-13 duty (solenoid loads) the rated values 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. The AC-15 rating at 690 V is 1 A. These numbers govern what inductive load you can switch reliably — match the voltage column to your control circuit. Surge voltage resistance is 6 kV, and the insulation voltage at pollution degree 3 is 690 V AC. ## Panel integration Dimensions are 44 mm wide, 38 mm tall, 51 mm deep — it adds minimal depth to the contactor stack. The note \"with 3RT1\" in the catalog means this block is specifically keyed for that contactor series, not the 3RT2.","metaTitle":"Siemens 3RH1921-1FA40 SIRIUS Auxiliary Switch Block, 4 NO, 1","metaDescription":"Siemens 3RH1921-1FA40 SIRIUS auxiliary switch block, 4 NO contacts, 10 A max, snap-on DIN mount. Phased-out product; successor is 3RH2 series. Sourced to order against 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":"4","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=518734&mlfb=3RH1921-1FA40","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA40/alternatives.json"},"ai":{"faq":[{"question":"Will 3RH1921-1FA40 drop into a panel specified around 3RH2140-1BP40?","answer":"No, the 3RH2140-1BP40 is a different form factor — it is 73 mm deep, 45 mm wide, and 57.5 mm tall, versus the 51 mm depth, 44 mm width, and 38 mm height of the 3RH1921-1FA40. The 3RH2140 also mounts with screws in addition to snap-on. They are not dimensionally interchangeable without panel rework."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-1FA40","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/3RH1921-1FA40 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}}