{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RH2122-4KB40","brand":"Siemens","brandSlug":"siemens","productSlug":"3RH2122-4KB40","canonicalUrl":"https://aoctrl.com/siemens/3RH2122-4KB40","factsUrl":"https://aoctrl.com/api/mcp/products/3RH2122-4KB40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS coupling relay 3RH2122-4KB40, S00 size, 24 VDC coil with suppressor diode, 2 instantaneous NO contacts, screw and snap-on mounting on 35 mm DIN rail.","salesMarkdown":"The Siemens 3RH2122-4KB40 is a SIRIUS coupling relay (product designation: coupling relay for switching auxiliary circuits) in the S00 contactor size. It is designed to switch auxiliary circuits in control panels, typically driven by a PLC or pushbutton signal to energize contactor coils, signal lamps, or small loads. Dimensions are 45 mm wide, 57.5 mm high, 73 mm deep — the 45 mm width is a standard modular increment, so it occupies one 45 mm slot on the rail. ## Switching capability and contact ratings The relay carries 2 instantaneous NO contacts. Rated switching currents are given at several voltage levels across AC and DC: 10 A at 24 V rated value, 10 A at 230 V rated value, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, 0.26 A at 600 V, and 1 A at 690 V. These are the maximum continuous currents the contacts can make and break at those voltages — for motor-circuit use, derate per the contactor's utilization category. The coil is 24 VDC with a built-in suppressor diode. Coil closing power is 2.8 W, holding power also 2.8 W — a DC coil that draws constant power, not an AC economizer circuit. The arcing time is 10–15 ms, and the relay is rated for 10,000 switching cycles per hour at AC and 7–20 ms at DC. Mechanical life is 30,000,000 operations typical. ## Clearance and panel integration These are the minimum air gaps to adjacent components or enclosure walls for proper heat dissipation and arc containment. When laying out a DIN rail, account for these clearances — the 45 mm width plus 6 mm side clearance on each side means an effective slot width of about 57 mm per relay in a multi-device row.","metaTitle":"Siemens 3RH2122-4KB40 SIRIUS Coupling Relay, 24 VDC, 2 NO Co","metaDescription":"Siemens 3RH2122-4KB40 SIRIUS coupling relay, 24 VDC coil, 2 NO contacts, S00 size, screw and snap-on DIN rail mounting. Rated 10 A at 24 V and 230 V. Current lifecycle stage. Quote","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Contactors"],"specifications":{"Depth":"73 mm","Width":"45 mm","at AC":"10 000 1/h","at DC":"7 ... 20 ms","title":"3RH2122-4KB40","Height":"57.5 mm","Upwards":"10 mm","Forwards":"10 mm","Downwards":"10 mm","Arcing Time":"10 ... 15 ms","At The Side":"6 mm","Rated Value":"24 V","description":"Coupling contactor relay, 2 NO + 2 NC, 24 V DC, 0.7... 1.25* US, with integrated suppressor diode, Size S00, Ring cable lug connection, suitable for PLC outputs","Initial Value":"0.7","During Storage":"-55 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting onto 35 mm DIN rail","Full-Scale Value":"1.25","Mounting Position":"+/-180° rotation possible on vertical mounting surface; can be tilted forward and backward by +/- 22.5° on vertical mounting surface","Size Of Contactor":"S00","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"Coupling relay for switching auxiliary circuits","at 24 V rated value":"10 A","at 60 V rated value":"4.7 A","Of Contactor Typical":"30 000 000","at 110 V rated value":"3 A","at 220 V rated value":"1.2 A","at 230 V rated value":"10 A","at 400 V rated value":"3 A","at 440 V rated value":"0.5 A","at 500 V rated value":"2 A","at 600 V rated value":"0.26 A","at 690 V rated value":"1 A","Instantaneous Contact":"2","Relative Humidity Minimum":"10 %","Substance Prohibitance (Date)":"10/01/2009","Design Of The Surge Suppressor":"suppressor diode","Product Extension Auxiliary Switch":"No","closing power of magnet coil at DC":"2.8 W","holding power of magnet coil at DC":"2.8 W","Surge Voltage Resistance Rated Value":"6 kV","operating frequency at DC-12 maximum":"1 000 1/h","operating frequency at DC-13 maximum":"1 000 1/h","operational current at AC-12 maximum":"10 A","reference code according to IEC 81346-2":"K","Contact Reliability Of Auxiliary Contacts":"1 faulty switching per 100 million (17 V, 1 mA)","with low demand rate according to SN 31920":"40 %","with high demand rate according to SN 31920":"73 %","number of NC contacts for auxiliary contacts":"2","number of NO contacts for auxiliary contacts":"2","Type Of Voltage Of The Control Supply Voltage":"DC","contact rating of auxiliary contacts according to UL":"A600 / Q600","Identification Number And Letter For Switching Elements":"22 E","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Type Of Electrical Connection For Auxiliary And Control Circuit":"ring terminal lug connection","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Design Of The Fuse Link For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 10 A","design of the miniature circuit breaker for short-circuit protection of the auxiliary circuit up to 230 V":"C characteristic: 6 A; 0.4 kA"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/36eec38425d277db220ea436f522b896.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=449013&mlfb=3RH2122-4KB40"},"ai":{"faq":[{"question":"What is the closest functional second-source to 3RH2122-4KB40?","answer":"The closest peer within the same SIRIUS family is the 3RH2122-1WB40, which shares the same S00 size, 2 NO contacts, and 24 VDC coil. The main difference is the -1WB40 variant may have a different suppressor or terminal arrangement — verify the specific coil code and accessory compatibility before substituting."},{"question":"Will 3RH2122-4KB40 drop into a panel specified around 3RH2122-1WB40 without rewiring?","answer":"Both are S00 size, same DIN rail mounting, same 45 mm width, same 2 NO contact configuration. The physical fit and terminal layout are identical — no rewiring of the DIN rail or enclosure cutouts needed. However, confirm the coil voltage (both 24 VDC) and any surge suppressor differences (the -4KB40 includes a suppressor diode; the -1WB40 may differ)."},{"question":"What compliance documentation does Siemens provide for 3RH2122-4KB40?","answer":"The part is RoHS-compliant per the substance prohibition date of 10/01/2009. Siemens typically provides a declaration of conformity (CE) and UL/CSA listings for the SIRIUS contactor family; check the specific certificate for the 3RH2122-4KB40 variant. REACH compliance is standard for current-production SIRIUS components."},{"question":"Where can I buy 3RH2122-4KB40 and how is it quoted?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time — submit an RFQ for your target quantity and delivery timeline."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RH2122-4KB40","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/3RH2122-4KB40 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}