{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU2126-4BC0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU2126-4BC0","canonicalUrl":"https://aoctrl.com/siemens/3RU2126-4BC0","factsUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4BC0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RU2126-4BC0 thermal overload relay, Size S0, Class 10 trip, 690 V rated insulation, spring-loaded terminals, for contactor mounting.","salesMarkdown":"The thermal bimetallic release provides Class 10 trip protection. The relay carries motor power ratings at several common line voltages: 7.5 kW at 400 V, 11 kW at 500 V, and 15 kW at 690 V. At 480 V and 600 V it's rated 20 A. That tells you the current range this S0 frame covers — it's sized for the smaller end of the SIRIUS contactor family, typically up to around 32 A motor FLC. The auxiliary contact ratings are given per voltage: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V — these are the make/break capacities for the trip-indication circuit, so if you're feeding a 24 VDC PLC input, the 2 A rating is plenty; if you're switching a 690 V control transformer, you're limited to 0.75 A. The spring-loaded terminals (cage-clamp style) accept 2× (0.5 to 2.5 mm²) solid or stranded — no screw torque to worry about, and no periodic re-torquing on a vibrating panel. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across the typical enclosure ambient range. Dimensions: 102 mm high, 45 mm wide, 84 mm deep. The depth of 84 mm includes the spring terminals; allow clearance for wire bending radius below the relay. The screwdriver slot for the terminal release is a 3 mm diameter shaft, tip size 3.0 × 0.5 mm — a standard slotted screwdriver, no special tool.","metaTitle":"Siemens 3RU2126-4BC0 SIRIUS Thermal Overload Relay, Size S0,","metaDescription":"Siemens 3RU2126-4BC0 SIRIUS thermal overload relay, Size S0, Class 10 trip, 690 V rated, spring terminals. Current production. Sourced to order. Request quote.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Overload Relays"],"specifications":{"Note":"for message \"Tripped\"","Depth":"84 mm","Width":"45 mm","Height":"102 mm","at 24 V":"2 A","at 60 V":"0.3 A","Per Pole":"2.7 W","at 110 V":"0.22 A","at 120 V":"3 A","at 125 V":"0.22 A","at 220 V":"0.11 A","at 230 V":"2 A","at 400 V":"1 A","at 690 V":"0.75 A","Trip Class":"CLASS 10","Rated Value":"690 V","During Storage":"-55 ... +80 °C","lifecycle_stage":"current","During Operation":"-40 ... +70 °C","During Transport":"-55 ... +80 °C","Fastening Method":"Contactor mounting","Mounting Position":"any","Solid Or Stranded":"2x (0.5 ... 2.5 mm²)","Product Brand Name":"SIRIUS","Product Designation":"thermal overload relay","at 400 V rated value":"7.5 kW","at 480 V rated value":"20 A","at 500 V rated value":"11 kW","at 600 V rated value":"20 A","at 690 V rated value":"15 kW","Size Of Overload Relay":"S0","For Main Current Circuit":"spring-loaded terminals","Temperature Compensation":"-40 ... +60 °C","MTTF with high demand rate":"2 280 a","Design Of Screwdriver Shaft":"Diameter 3 mm","Size Of The Screwdriver Tip":"3,0 x 0,5 mm","at AC-3e rated value maximum":"690 V","Substance Prohibitance (Date)":"10/01/2009","Design Of The Auxiliary Switch":"integrated","Design Of The Overload Release":"thermal","Operating Frequency Rated Value":"50 ... 60 Hz","Operational Current Rated Value":"20 A","at AWG cables for main contacts":"1x (18 ... 8)","For Auxiliary And Control Circuit":"spring-loaded terminals","Between Main And Auxiliary Circuit":"440 V","Relative Humidity During Operation":"10 ... 95 %","Display Version For Switching Status":"Slide switch","Surge Voltage Resistance Rated Value":"6 kV","at AWG cables for auxiliary contacts":"2x (20 ... 14)","Between Auxiliary And Auxiliary Circuit":"440 V","reference code according to IEC 81346-2":"F","Finely Stranded With Core End Processing":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)","Number Of Poles For Main Current Circuit":"3","Finely Stranded Without Core End Processing":"2x (0.5 ... 1.5 mm²)","number of CO contacts for auxiliary contacts":"0","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","shock resistance according to IEC 60068-2-27":"8g / 11 ms","operational current at AC-3e at 400 V rated value":"20 A","Size Of Contactor Can Be Combined Company-Specific":"S0","contact rating of auxiliary contacts according to UL":"B600 / R300","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Arrangement Of Electrical Connectors For Main Current Circuit":"Top and bottom","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gG: 6 A, quick: 10 A","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Product Component Removable Terminal For Auxiliary And Control Circuit":"No","power loss [W] for rated value of the current at AC in hot operating state":"8.1 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"14 ... 20 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$30.48","priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/a206ee805963d384bf741e02144b4b5f.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=488535&mlfb=3RU2126-4BC0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4BC0/alternatives.json"},"ai":{"faq":[{"question":"Will 3RU2126-4BC0 drop into a panel that was specified around 3RU2116-1FC1 without rewiring?","answer":"Both are SIRIUS Size S0 thermal overload relays with the same mounting footprint and terminal layout, so they are mechanically interchangeable. However, the 3RU2126-4BC0 has a different current adjustment range and auxiliary contact ratings — verify the motor FLC and control voltage against the datasheet before swapping."},{"question":"What is 3RU2126-4BC0's listed note (for message 'Tripped') on this component line?","answer":"The note field reads 'for message \"Tripped\"' — this is a labeling or diagnostic string used in Siemens engineering tools or HMI faceplates to indicate the relay has tripped. It's not a functional spec."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU2126-4BC0","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/3RU2126-4BC0 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}}