{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2123-4PB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2123-4PB0","canonicalUrl":"https://aoctrl.com/siemens/3RB2123-4PB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4PB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2123-4PB0, 45 mm width, contactor mounting, adjustable trip class 5E/10E/20E/30E, IP20 front, ATEX Ex II (2) GD.","salesMarkdown":"The Siemens 3RB2123-4PB0 is a SIRIUS solid-state overload relay — no bimetals to drift, no heater packs to swap. It mounts directly onto a contactor (contactor mounting) and protects motors against phase loss, overload, and prolonged start conditions. The trip class is field-adjustable among CLASS 5E, 10E, 20E and 30E, so you can match the relay to the motor's starting profile without stocking four different units. Width is 45 mm — a single module slot on a contactor assembly. Depth is 75 mm, height 73 mm. Auxiliary contact ratings are given per voltage: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.55 A at 60 V, 0.3 A at 125 V, 0.11 A at 220 V — these govern the control-circuit load the relay can switch directly (PLC inputs, contactor coils, indicators). The main circuit terminals are screw-type, accepting solid conductors 0.5... 4 mm² (or 2x 0.5... 2.5 mm²). AWG equivalents for the main contacts are 2x (14... 10). Side clearance of 6 mm is needed; forward, backward, upward, and downward clearance is 0 mm — it can butt against other components on those faces. Operating temperature range is -25... +60 °C; storage/transport range is -40... +80 °C. Shock resistance is rated 15g / 11 ms.","metaTitle":"Siemens 3RB2123-4PB0 SIRIUS Solid-State Overload Relay, 45 m","metaDescription":"Siemens SIRIUS 3RB2123-4PB0 solid-state overload relay, 45 mm wide, contactor-mount, adjustable trip class 5E–30E, ATEX Ex II (2) GD. Sourced to order against RFQ.","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","Maximum":"2 000 m","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","During Storage":"-40 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","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 Auxiliary Contacts":"0","For Main Current Circuit":"screw-type terminals","at AC-3 rated value maximum":"690 V","at AC in hot operating state":"0.05 W","Relative humidity during operation":"100 %","due to burst acc. to IEC 61000-4-4":"2 kV (power ports), 1 kV (signal ports) corresponds to degree of severity 3","at AWG conductors for main contacts":"2x (14 ... 10)","Surge voltage resistance rated value":"6 kV","Reference code acc. to DIN EN 81346-2":"F","at AC in hot operating state per pole":"0.02 W","With Degree Of Pollution 3 Rated Value":"690 V","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","at AWG conductors for auxiliary contacts":"2x (20 ... 14)","For Auxiliary And Control Current Circuit":"screw-type terminals","Number of NC contacts for auxiliary contacts":"1","Number of NO contacts for auxiliary contacts":"1","Electrostatic discharge acc. to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Size of contactor can be combined company-specific":"S0","due to conductor-earth surge acc. to IEC 61000-4-5":"2 kV (line to earth) corresponds to degree of severity 3","Removable Terminal For Auxiliary And Control Circuit":"Yes","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 6 A","Adjustable pick-up value current of the current-dependent overload release":"1 ... 4 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$156.08","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=498846&mlfb=3RB2123-4PB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4PB0/alternatives.json"},"ai":{"faq":[{"question":"Who supplies 3RB2123-4PB0 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."},{"question":"What is the closest functional second-source to 3RB2123-4PB0?","answer":"The closest functional peer is the 3RU2116-1FC1, a bimetallic overload relay from the same SIRIUS family. The 3RB2123-4PB0 is solid-state with adjustable trip class; the 3RU is thermal with fixed or selectable class. They share the same contactor-mounting footprint, so a panel designed for the 3RU can accept the 3RB without rewiring, but the trip curve behavior differs — the solid-state unit offers faster, more repeatable protection and wider class adjustability."},{"question":"What is the depth of 3RB2123-4PB0?","answer":"The depth is 75 mm."},{"question":"What conductor sizes does the 3RB2123-4PB0 accept?","answer":"The main circuit screw terminals accept solid conductors 0.5... 4 mm² (or 2x 0.5... 2.5 mm²); AWG equivalents are 2x (14... 10)."},{"question":"What compliance documentation does the 3RB2123-4PB0 carry?","answer":"It carries ATEX approval PTB 06 ATEX 3001 Ex II (2) GD, surge voltage resistance 6 kV, and burst immunity per IEC 61000-4-4 severity 3. Pollution degree 3 rated at 690 V."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2123-4PB0","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/3RB2123-4PB0 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}}