{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2123-4SB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2123-4SB0","canonicalUrl":"https://aoctrl.com/siemens/3RB2123-4SB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4SB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2123-4SB0, S0 contactor size, 690 V AC-3 max, adjustable trip class 5E/10E/20E/30E, 1 NO + 1 NC auxiliary contacts, screw terminals, IP20 front, ATEX Ex II (2) GD.","salesMarkdown":"The Siemens 3RB2123-4SB0 is a SIRIUS solid-state overload relay sized for S0 contactors, protecting three-phase motor circuits up to 690 V AC-3 with adjustable trip classes 5E, 10E, 20E, or 30E — so you match the trip curve to the motor start profile (fast for submersible pumps, slow for high-inertia fans). It mounts directly onto the contactor (no separate DIN-rail footprint needed), saving panel width — the body is 45 mm wide and 75 mm deep, which keeps the contactor/overload pair within a single S0 slot. The front face carries IP20 touch protection, and the unit is ATEX certified Ex II (2) GD for use in potentially explosive gas and dust atmospheres. The auxiliary contact block gives you one NO and one NC contact — enough for a basic run-status feedback and a fault signal back to the PLC, without needing a separate auxiliary contactor. Switching capacity varies with control voltage: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V — these are the make/break ratings for the aux contacts, so size your PLC input or relay coil draw accordingly. Rated surge voltage withstand is 6 kV, and ESD protection meets IEC 61000-4-2 at 6 kV contact / 8 kV air discharge — the relay can live in a panel with drives or contactors without extra suppression on the aux circuit. Operating temperature range is -25 to +60 °C, storage/transport -40 to +80 °C, with 100 % relative humidity allowed — fine for unheated plant rooms or washdown areas as long as the enclosure keeps direct spray off the IP20 front. Shock rated at 15 g for 11 ms; mounting position is any orientation — install it vertically, horizontally, or upside-down without derating.","metaTitle":"Siemens 3RB2123-4SB0 SIRIUS Solid-State Overload Relay, S0,","metaDescription":"Siemens 3RB2123-4SB0 SIRIUS solid-state overload relay, S0 size, 690 V AC-3 max, adjustable trip class 5E-30E, 1 NO+1 NC aux contacts, ATEX Ex II (2) GD. Sourced to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"75 mm","Width":"45 mm","Height":"73 mm","Upwards":"0 mm","at 24 V":"2 A","at 60 V":"0.55 A","Forwards":"0 mm","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","On The Front":"IP20","Mounting Type":"Contactor mounting","lifecycle_stage":"current","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","Ambient Temperature During Storage":"-40 ... +80 °C","Relative Humidity During Operation":"100 %","Ambient Temperature During Operation":"-25 ... +60 °C","Ambient Temperature During Transport":"-40 ... +80 °C","Surge Voltage Resistance Rated Value":"6 kV","reference code acc. to DIN EN 81346-2":"F","Number Of Poles For Main Current Circuit":"3","For Auxiliary And Control Current Circuit":"screw-type terminals","number of CO contacts for auxiliary contacts":"0","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","with degree of pollution 3 at AC rated value":"690 V","electrostatic discharge acc. to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","operating voltage at AC-3 rated value maximum":"690 V","Size Of Contactor Can Be Combined Company-Specific":"S0","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Type Of Connectable Conductor Cross-Sections For Main Contacts Solid":"2x (1 ... 2.5 mm²), 2x (2.5 ... 6 mm²)","Product Function Removable Terminal For Auxiliary And Control Circuit":"Yes","Type Of Connectable Conductor Cross-Sections For Auxiliary Contacts Solid":"0.5 ... 4 mm², 2x (0.5 ... 2.5 mm²)","Adjustable Pick-Up Value Current Of The Current-Dependent Overload Release":"3 ... 12 A","power loss [W] for rated value of the current at AC in hot operating state":"0.05 W","type of connectable conductor cross-sections at AWG conductors for main contacts":"2x (14 ... 10)","power loss [W] for rated value of the current at AC in hot operating state per pole":"0.02 W","Design Of The Fuse Link For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 6 A","type of connectable conductor cross-sections at AWG conductors for auxiliary contacts":"2x (20 ... 14)","Type Of Connectable Conductor Cross-Sections For Main Contacts Finely Stranded With Core End Processing":"2x (1 ... 2.5 mm²), 2x (2.5 ... 6 mm²)","Type Of Connectable Conductor Cross-Sections For Auxiliary Contacts Finely Stranded With Core End Processing":"0.5 ... 2.5 mm², 2x (0.5 ... 1.5 mm²)"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$96.38","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=6186&mlfb=3RB2123-4SB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4SB0/alternatives.json"},"ai":{"faq":[{"question":"What trip classes does the 3RB2123-4SB0 support?","answer":"It supports adjustable trip classes 5E, 10E, 20E, and 30E — selectable via the front dial to match the motor start time."},{"question":"Does the 3RB2123-4SB0 have ATEX certification?","answer":"Yes, it carries PTB 06 ATEX 3001 Ex II (2) GD certification for use in gas and dust explosive atmospheres."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2123-4SB0","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/3RB2123-4SB0 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}}