{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-1FA22","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-1FA22","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-1FA22","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA22","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 4-pole 2 NO + 2 NC, snap-on mounting for 3RT1 contactors, screw terminals, 10 A maximum, 51 mm depth.","salesMarkdown":"The Siemens 3RH1921-1FA22 is a 4-pole attachable auxiliary switch block from the SIRIUS family, configured 2 NO + 2 NC per EN 50005. It snaps onto 3RT1 contactors and contactor relays, adding auxiliary contacts for status feedback, interlocking, or control logic without extra wiring space. The block carries a 10 A maximum thermal current and is rated for AC-15 switching at 690 V up to 1 A, with a surge voltage resistance of 6 kV and insulation voltage of 690 V at pollution degree 3. Mechanical service life is 10 million switching cycles typical, with contact reliability of 1 faulty switching per 100 million operations at 17 V, 1 mA. ## Contact ratings across voltages The block's contact ratings are specified per voltage for DC auxiliary circuits: 10 A at 24 V, 6 A at 125 V and 230 V, 4.7 A at 60 V, 3 A at 110 V and 400 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. These values govern the maximum switching current at each voltage level — match them to your control circuit's voltage and load to avoid overstressing the contacts. ## Lifecycle and replacement This part is marked as a phased-out product. The official successor is the SIRIUS 3RH2 series. For new designs or BOM freeze replacements, the 3RH2122-1WB40 is the closest functional peer — same 2 NO + 2 NC configuration, same 10 A at 24 V DC rating, same screw terminals, but with a larger footprint (73 mm depth vs 51 mm, 45 mm width vs 44 mm) and a higher mechanical life of 30 million cycles. Snap-on mounting directly onto the 3RT1 contactor — no DIN rail required for the block itself. Screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20 to 16) and 2x (18 to 14) AWG.","metaTitle":"Siemens 3RH1921-1FA22 SIRIUS Auxiliary Switch Block, 2NO+2NC","metaDescription":"Siemens 3RH1921-1FA22 SIRIUS attachable auxiliary switch block, 4-pole 2NO+2NC, 10A max, snap-on mounting for 3RT1 contactors. 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":"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 (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":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=43530&mlfb=3RH1921-1FA22","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1FA22/alternatives.json"},"ai":{"faq":[{"question":"What replaces 3RH1921-1FA22?","answer":"The official successor is the SIRIUS 3RH2 series. The closest functional peer is 3RH2122-1WB40 — same 2 NO + 2 NC contacts, same 10 A at 24 V DC rating, same screw terminals, but with a larger 73 mm depth and 45 mm width, and requiring screw-and-snap-on mounting onto 35 mm DIN rail."},{"question":"What is the note 'with 3RT1' on this part?","answer":"The note indicates this auxiliary switch block is designed to snap onto Siemens 3RT1 contactors and contactor relays. It is not a standalone device — it attaches to the 3RT1 base unit."},{"question":"What are the key contact ratings for 3RH1921-1FA22?","answer":"Maximum thermal current is 10 A. DC contact ratings include 10 A at 24 V, 6 A at 125 V and 230 V, 3 A at 110 V and 400 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. AC-15 rating at 690 V is 1 A."},{"question":"Where can I buy 3RH1921-1FA22?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time."},{"question":"Will 3RH1921-1FA22 drop into a panel specified around 3RH2122-1WB40?","answer":"Not without changes. The 3RH1921-1FA22 is smaller (51 mm depth, 44 mm width) and snaps onto a 3RT1 contactor. The 3RH2122-1WB40 is larger (73 mm depth, 45 mm width) and mounts on 35 mm DIN rail. Panel layout, rail space, and wiring must be reviewed before substituting."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-1FA22","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/3RH1921-1FA22 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}}