{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2123-4ND0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2123-4ND0","canonicalUrl":"https://aoctrl.com/siemens/3RB2123-4ND0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4ND0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3-pole, screw-type main terminals, spring-loaded aux terminals, adjustable trip classes 5E/10E/20E/30E, ATEX Ex II (2) GD, 75 mm depth, 45 mm width.","salesMarkdown":"The Siemens 3RB2123-4ND0 is a SIRIUS solid-state overload relay for three-phase motor protection. It mounts directly to a contactor — no separate DIN-rail footprint needed — and provides adjustable trip classes 5E, 10E, 20E, and 30E, so you can match the thermal curve to the motor start profile (fast for pumps, slow for high-inertia loads). The ATEX Ex II (2) GD marking means it's certified for use in potentially explosive atmospheres, covering both gas and dust zones. Main circuit connections use screw-type terminals; the auxiliary and control circuit uses spring-loaded terminals for faster wiring. The adjustable trip class is the headline feature: set it to 5E for quick-trip protection on short-start motors, or 30E for high-inertia loads like centrifuges. The 3-pole design covers standard three-phase motor circuits. Surge voltage resistance is rated at 6 kV, and the relay withstands burst transients at 2 kV on power ports and 1 kV on signal ports per IEC 61000-4-4 severity level 3 — enough for industrial environments with contactor switching and VFD noise. Fastening method is contactor mounting — it clips directly onto the matching SIRIUS contactor, saving DIN-rail space. Dimensions: 45 mm wide, 73 mm high, 75 mm deep. Mounting position is any. Main circuit accepts 2x (0.25... 1.5 mm²) solid or finely stranded with ferrule, or 2x (14... 10) AWG. Auxiliary circuit uses spring-loaded terminals for 2x (24... 16) AWG.","metaTitle":"Siemens 3RB2123-4ND0 SIRIUS Solid-State Overload Relay, ATEX","metaDescription":"Siemens 3RB2123-4ND0 SIRIUS solid-state overload relay. 3-pole, adjustable trip classes 5E/10E/20E/30E. ATEX Ex II (2) GD. 75 mm depth. Current production. Quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"75 mm","Solid":"2x (0.25 ... 1.5 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":"spring-loaded terminals","Relative Humidity During Operation":"100 %","Surge Voltage Resistance Rated Value":"6 kV","at AWG cables for auxiliary contacts":"2x (24 ... 16)","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":"2x (0.25 ... 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":"0.32 ... 1.25 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=257141&mlfb=3RB2123-4ND0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4ND0/alternatives.json"},"ai":{"faq":[{"question":"What trip classes can the 3RB2123-4ND0 be set to?","answer":"The trip class is adjustable to CLASS 5E, 10E, 20E, or 30E. This lets you match the overload curve to the motor's starting characteristics."},{"question":"What ATEX rating does this overload relay carry?","answer":"It carries PTB 06 ATEX 3001 Ex II (2) GD certification, suitable for gas and dust explosive atmospheres."},{"question":"Where can I buy the 3RB2123-4ND0 and how is it quoted?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution channels. Availability and current pricing are confirmed at quote time."},{"question":"Does the 3RB2123-4ND0 mount on a DIN rail or directly to a contactor?","answer":"It uses contactor mounting — it clips directly onto the matching SIRIUS contactor, not onto a DIN rail."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2123-4ND0","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/3RB2123-4ND0 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}}