{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU2126-4PC0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU2126-4PC0","canonicalUrl":"https://aoctrl.com/siemens/3RU2126-4PC0","factsUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4PC0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RU2126-4PC0 thermal overload relay, CLASS 10, size S0, 690 V rated, 18.5 kW at 400 V, spring-loaded terminals, contactor mounting.","salesMarkdown":"The Siemens 3RU2126-4PC0 is a SIRIUS-branded thermal overload relay, size S0, designed for motor protection in a control panel. It mounts directly onto a contactor, saving DIN-rail space — the fastening method is contactor mounting, so it stacks on the load side of the matching S0 contactor rather than taking up its own rail slot. That's the standard for standard-duty motor starts — pumps, fans, compressors that don't need a longer acceleration curve. For a motor that takes longer to spin up, you'd step to CLASS 20 or 30; this one is for normal across-the-line starts. Rated insulation voltage is 690 V, with motor power ratings of 18.5 kW at 400 V, 22 kW at 500 V, and 30 kW at 690 V. The auxiliary switch is integrated — no separate add-on block needed for the trip/alarm signal. Terminals are spring-loaded, accepting 2× (0.5 to 2.5 mm²) solid or stranded, which speeds up wiring compared to screw-clamp on the same footprint. The auxiliary contact ratings cover a range of control voltages: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V. At 60 V and 125 V the rating drops to 0.3 A and 0.22 A respectively, which matters if you're switching a DC control circuit at those levels. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across the panel's ambient range. The MTTF at high demand rate is 2,280 years — a reliability figure that reflects the thermal bimetal design with no electronics to fail. Dimensions are 45 mm wide, 102 mm high, 84 mm deep — the S0 footprint. That's the same width as the matching S0 contactor, so the stack takes up one 45 mm slot in the panel. Mounting position is any, which helps when the panel layout is tight. The substance prohibitance date is October 1, 2009, which aligns with RoHS compliance — the part meets the EU RoHS directive for hazardous substances. The SIRIUS series carries CE, UL, CSA, and other international approvals as standard for Siemens industrial controls, though the specific cert marks aren't listed in this spec set. For a compliance binder, the manufacturer's declaration and the product label are the traceable documents.","metaTitle":"Siemens 3RU2126-4PC0 SIRIUS Thermal Overload Relay, CLASS 10","metaDescription":"Siemens 3RU2126-4PC0 SIRIUS thermal overload relay, CLASS 10 trip, S0 size, 690V rated, 18.5kW at 400V. Current production. RFQ for BOM line.","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":"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","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":"18.5 kW","at 480 V rated value":"36 A","at 500 V rated value":"22 kW","at 600 V rated value":"36 A","at 690 V rated value":"30 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 y","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":"36 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":"36 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":"9.6 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"30 ... 36 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/817e6e6542e38fb845f0812c2a7465b6.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=211232&mlfb=3RU2126-4PC0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4PC0/alternatives.json"},"ai":{"faq":[{"question":"What does the note \"for message Tripped\" mean on this relay?","answer":"The note indicates that the integrated auxiliary switch is wired to signal a \"Tripped\" status — it's the normally-open contact that closes when the relay trips from an overload. That contact is rated at the listed voltages and currents (e.g., 2 A at 24 V, 3 A at 120 V) and is used to send a trip signal to a PLC, HMI, or alarm light."},{"question":"What are the key ratings for the 3RU2126-4PC0?","answer":"It's a CLASS 10 thermal overload relay, size S0, rated 690 V insulation voltage. Motor power ratings are 18.5 kW at 400 V, 22 kW at 500 V, and 30 kW at 690 V. The auxiliary contact switches 2 A at 24 V, 3 A at 120 V, and 1 A at 400 V. Terminals are spring-loaded, accepting 2× (0.5 to 2.5 mm²) conductors."},{"question":"Does the 3RU2126-4PC0 mount on a DIN rail or directly on a contactor?","answer":"It mounts directly on the contactor — the fastening method is contactor mounting, not DIN rail. It stacks on the load side of the matching S0 contactor (e.g., the 3RT20 series), saving a DIN-rail slot in the panel."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU2126-4PC0","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/3RU2126-4PC0 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}}