{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU2126-4FJ0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU2126-4FJ0","canonicalUrl":"https://aoctrl.com/siemens/3RU2126-4FJ0","factsUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4FJ0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RU2126-4FJ0 thermal overload relay, Size S0, Trip Class 10, rated 690 V, 18.5 kW at 400 V, with integrated auxiliary switch.","salesMarkdown":"## What This Relay Does on the Line Rated for main circuits up to 690 V, it handles 18.5 kW at 400 V, 22 kW at 500 V, and 37 kW at 690 V. The 480 V and 600 V ratings both list 40 A, so it covers North American 480Y/277 V and 600 V delta systems cleanly. The built-in auxiliary switch provides status feedback — a tripped message is signaled on the auxiliary contact set, which is what the \"Note for message 'Tripped'\" spec refers to. This lets a PLC or annunciator panel see the relay state without extra hardware. ## Mounting and Wiring in the Panel Mounts directly onto a contactor (contactor mounting), in any position. The S0 footprint is 45 mm wide by 85 mm deep — fits standard DIN-rail enclosures without overhang. Main circuit connections use ring cable lugs with M4 screws; auxiliary connections use Pozidriv PZ2 screwdriver tips, 5–6 mm shaft diameter. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate even in hot enclosures or cold outdoor installations. The integrated auxiliary switch is rated for both AC and DC control circuits. At 24 V DC it switches 2 A; at 120 V AC it switches 3 A; at 230 V AC it switches 2 A; at 400 V AC it handles 1 A. For DC applications at higher voltages, derate to 0.3 A at 60 V, 0.22 A at 110/125 V, and 0.11 A at 220 V. These are the maximum breaking currents — your PLC output card or relay coil must stay within these limits. Per-pole power dissipation is 3.2 W. In a dense panel with multiple relays, factor this into the thermal budget — the S0 frame dissipates heat through the contactor base, so keep airflow around the mounting rail.","metaTitle":"Siemens 3RU2126-4FJ0 SIRIUS Thermal Overload Relay, Class 10","metaDescription":"Siemens 3RU2126-4FJ0 SIRIUS thermal overload relay, Size S0, Trip Class 10, rated 690V, 18.5 kW at 400V. Current lifecycle stage, available to order. Quoted on request.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Note":"for message \"Tripped\"","Depth":"85 mm","Width":"45 mm","Height":"85 mm","at 24 V":"2 A","at 60 V":"0.3 A","Per Pole":"3.2 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","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","For Main Contacts":"M4","Mounting Position":"any","Product Brand Name":"SIRIUS","Product Designation":"thermal overload relay","at 400 V rated value":"18.5 kW","at 480 V rated value":"40 A","at 500 V rated value":"22 kW","at 600 V rated value":"40 A","at 690 V rated value":"37 kW","Size Of Overload Relay":"S0","For Main Current Circuit":"Ring cable lug connection","Temperature Compensation":"-40 ... +60 °C","MTTF with high demand rate":"2 280 y","Design Of Screwdriver Shaft":"Diameter 5 ... 6 mm","Size Of The Screwdriver Tip":"Pozidriv PZ 2","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":"40 A","For Auxiliary And Control Circuit":"ring terminal lug connection","Between Main And Auxiliary Circuit":"440 V","Relative Humidity During Operation":"10 ... 95 %","Display Version For Switching Status":"Slide switch","For Main Contacts For Ring Cable Lug":"2.5 ... 2 N·m","Surge Voltage Resistance Rated Value":"6 kV","Of The Auxiliary And Control Contacts":"M3","Between Auxiliary And Auxiliary Circuit":"440 V","reference code according to IEC 81346-2":"F","Number Of Poles For Main Current Circuit":"3","For Auxiliary Contacts For Ring Cable Lug":"0.8 ... 1.2 N·m","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":"40 A","Size Of Contactor Can Be Combined Company-Specific":"S0","Outer Diameter Of The Usable Ring Cable Lug Maximum":"7.5 mm","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":"9.6 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"34 ... 40 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=281103&mlfb=3RU2126-4FJ0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4FJ0/alternatives.json"},"ai":{"faq":[{"question":"What does the 'Note for message Tripped' mean on this relay?","answer":"It means the integrated auxiliary switch changes state when the relay trips from an overload or phase failure. That contact closure can be wired to a PLC input or alarm lamp to signal a tripped condition."},{"question":"What are the key ratings for the 3RU2126-4FJ0?","answer":"Trip Class 10, rated insulation voltage 690 V, power ratings of 18.5 kW at 400 V, 22 kW at 500 V, and 37 kW at 690 V. Auxiliary contacts handle 3 A at 120 V AC and 2 A at 24 V DC."},{"question":"Where can I buy the 3RU2126-4FJ0 and how is it quoted?","answer":"We source and quote this part to order against an RFQ. Availability and current pricing are confirmed at quote time through our independent distribution network. Submit an RFQ for your target quantity."},{"question":"Will the 3RU2126-4FJ0 fit a panel designed for the 3RU2116-1FC1?","answer":"Both are SIRIUS Size S0 overload relays with the same 45×85 mm footprint and contactor-mounting interface. The 3RU2126-4FJ0 has higher current and power ratings, so check that your motor FLA falls within its adjustment range. Mechanical fit is identical."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU2126-4FJ0","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/3RU2126-4FJ0 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}}