{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2123-4RB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2123-4RB0","canonicalUrl":"https://aoctrl.com/siemens/3RB2123-4RB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4RB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2123-4RB0, 3-pole, screw-type terminals, adjustable trip Class 5E/10E/20E/30E, ATEX Ex II (2) GD, active.","salesMarkdown":"The Siemens 3RB2123-4RB0 is a SIRIUS-brand solid-state overload relay for three-phase motor protection in control panels. It mounts directly to a contactor (fastening method: contactor mounting) and uses screw-type terminals for both the main current circuit and auxiliary/control circuits. The relay is rated for 3 poles and carries ATEX certification (PTB 06 ATEX 3001 Ex II (2) GD), making it suitable for installation in potentially explosive atmospheres where motor protection is required. ## Mechanical integration and wiring Dimensions are 45 mm wide, 73 mm high, and 75 mm deep — a compact 45 mm footprint that occupies one standard DIN-rail mounting position when attached to a contactor. Mounting position is any orientation, with zero clearance required upwards, forwards, backwards, and downwards; 6 mm clearance needed at the side for airflow or wiring access. Main circuit terminals accept solid conductors from 0.5 to 4 mm² (or 2x 0.5 to 2.5 mm²), and AWG 14–10 for the main contacts. Auxiliary and control circuit terminals accept 2x AWG 20–14. Finely stranded wire with ferrule is supported: 0.5 to 2.5 mm² single, 2x 0.5 to 1.5 mm². This covers standard motor power wiring up to approximately 4 mm² (roughly 12 AWG) for the main circuit. The product is RoHS compliant with substance prohibition date of 07/01/2006.","metaTitle":"Siemens 3RB2123-4RB0 SIRIUS solid-state overload relay, adju","metaDescription":"Siemens SIRIUS 3RB2123-4RB0 solid-state overload relay, 3-pole, screw terminals, adjustable trip Class 5E-30E, ATEX, active production. Sourced to order. Depth 75 mm.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"75 mm","Solid":"0.5 ... 4 mm², 2x (0.5 ... 2.5 mm²)","Width":"45 mm","Height":"73 mm","Upwards":"0 mm","at 24 V":"2 A","at 60 V":"0.55 A","Forwards":"0 mm","Per Pole":"0.02 W","at 110 V":"0.3 A","at 120 V":"4 A","at 125 V":"0.3 A","at 220 V":"0.11 A","at 230 V":"3 A","Backwards":"0 mm","Downwards":"0 mm","Trip Class":"CLASS 5E, 10E, 20E and 30E adjustable","At The Side":"6 mm","During Storage":"-40 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","Fastening Method":"Contactor mounting","Shock Resistance":"15g / 11 ms","Mounting Position":"any","Product Brand Name":"SIRIUS","Type Of Protection":"PTB 06 ATEX 3001 Ex II (2) GD","Product Designation":"solid-state overload relay","For Main Current Circuit":"screw-type terminals","Substance Prohibitance (Date)":"07/01/2006","at AWG cables for main contacts":"2x (14 ... 10)","For Auxiliary And Control Circuit":"screw-type terminals","Relative Humidity During Operation":"100 %","Surge Voltage Resistance Rated Value":"6 kV","at AWG cables for auxiliary contacts":"2x (20 ... 14)","due to burst according to IEC 61000-4-4":"2 kV (power ports), 1 kV (signal ports) corresponds to degree of severity 3","reference code according to IEC 81346-2":"F","Finely Stranded With Core End Processing":"0.5 ... 2.5 mm², 2x (0.5 ... 1.5 mm²)","Number Of Poles For Main Current Circuit":"3","number of CO contacts for auxiliary contacts":"0","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","Size Of Contactor Can Be Combined Company-Specific":"S0","electrostatic discharge according to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 6 A","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Product Component Removable Terminal For Auxiliary And Control Circuit":"Yes","power loss [W] for rated value of the current at AC in hot operating state":"0.05 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"0.1 ... 0.4 A"}},"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=189589&mlfb=3RB2123-4RB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4RB0/alternatives.json"},"ai":{"faq":[{"question":"What is the depth of the 3RB2123-4RB0?","answer":"The depth is 75 mm. Combined with a width of 45 mm and height of 73 mm, it fits a standard compact overload relay footprint for contactor mounting."},{"question":"What wire sizes does the 3RB2123-4RB0 accept?","answer":"The main circuit terminals accept solid conductors 0.5 to 4 mm² (or 2x 0.5 to 2.5 mm²), AWG 14–10. Auxiliary terminals accept 2x AWG 20–14. Finely stranded with ferrule: 0.5 to 2.5 mm² single, 2x 0.5 to 1.5 mm²."},{"question":"What compliance certifications does the 3RB2123-4RB0 carry?","answer":"It carries ATEX certification PTB 06 ATEX 3001 Ex II (2) GD for explosive atmospheres, RoHS compliance (substance prohibition date 07/01/2006), and EMC immunity per IEC 61000-4-4 severity level 3. Surge voltage resistance is rated at 6 kV."},{"question":"Can this relay be adjusted for different motor start characteristics?","answer":"Yes, the trip class is field-adjustable among CLASS 5E, 10E, 20E, and 30E. This lets you match the overload curve to the motor's starting profile — fast trip for short-time rated motors, slow trip for high-inertia loads."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2123-4RB0","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/3RB2123-4RB0 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}}