{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH1921-1MA20","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH1921-1MA20","canonicalUrl":"https://aoctrl.com/siemens/3RH1921-1MA20","factsUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1MA20","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS auxiliary switch block, 3RH1921-1MA20, 2 NC contacts, 10 A max, screw-type terminals, snap-on mounting for 3RT1 contactors.","salesMarkdown":"It's rated for a maximum of 10 A and carries a 690 V insulation voltage with degree of pollution 3, so it's built for industrial control panels where contactors are switching motor loads. The screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or the AWG equivalents 2x (20 to 16) and 2x (18 to 14). Snap-on mounting onto the contactor means no tools needed for installation — just push it onto the 3RT1 base unit until it latches. Dimensions are 44 mm wide, 38 mm tall, and 51 mm deep, which keeps the assembly compact alongside the contactor. The 3RH1921-1MA20 carries 2 NC contacts only. The successor 3RH2122-1WB40 carries 2 NO and 2 NC, so if your circuit needs both normally-open and normally-closed auxiliary contacts, the replacement block gives you that flexibility. The 3RH2 blocks are also slightly larger — 45 mm wide and 73 mm deep versus the 3RH1921's 44 mm by 51 mm — so verify panel clearance before swapping.","metaTitle":"Siemens 3RH1921-1MA20 SIRIUS Auxiliary Switch Block, 2 NC, 1","metaDescription":"Siemens SIRIUS 3RH1921-1MA20 auxiliary switch block, 2 NC contacts, 10 A max, snap-on for 3RT1 contactors. Phased-out; successor is 3RH2 series. Sourced to order.","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=346213&mlfb=3RH1921-1MA20","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RH1921-1MA20/alternatives.json"},"ai":{"faq":[{"question":"Where can I buy 3RH1921-1MA20 and how do I get a price?","answer":"We source this part to order against an RFQ through independent distribution channels. Submit a request for quote (RFQ) and we'll confirm availability and current pricing at quote time."},{"question":"What is the closest functional second-source for 3RH1921-1MA20?","answer":"The official successor is the SIRIUS 3RH2 series. For example, 3RH2122-1WB40 is a coupling relay with 2 NO + 2 NC contacts and the same 10 A rating, but it's physically deeper (73 mm vs 51 mm) and requires a 35 mm DIN rail mount. The 3RH1921-1MA20 snaps directly onto a 3RT1 contactor without needing its own DIN-rail clip."},{"question":"What does the note 'with 3RT1' mean for 3RH1921-1MA20?","answer":"It means this auxiliary switch block is designed to snap onto Siemens SIRIUS 3RT1 motor contactors. It's not a standalone device — it mounts directly on the contactor to add auxiliary contacts."},{"question":"What is the depth of 3RH1921-1MA20?","answer":"The depth is 51 mm. Width is 44 mm, height is 38 mm."},{"question":"Will 3RH1921-1MA20 drop into a panel specified around 3RH2122-1WB40 without rewiring?","answer":"No. The 3RH1921-1MA20 is 51 mm deep and mounts onto a 3RT1 contactor; the 3RH2122-1WB40 is 73 mm deep and mounts separately onto a 35 mm DIN rail. The wiring range is the same (screw terminals, 0.5–2.5 mm²), but the physical footprint and mounting method differ, so panel layout changes are needed."},{"question":"What compliance documentation does Siemens provide for 3RH1921-1MA20?","answer":"The part carries a 690 V insulation voltage rating (degree of pollution 3) and a 6 kV surge voltage resistance. It's a Siemens SIRIUS product, so standard CE, UL, and CSA certifications apply for industrial control equipment, though specific cert numbers are not listed in the available specs."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH1921-1MA20","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/3RH1921-1MA20 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}}