{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU2126-4PC1","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU2126-4PC1","canonicalUrl":"https://aoctrl.com/siemens/3RU2126-4PC1","factsUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4PC1","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS S0 thermal overload relay, 3RU2126-4PC1, Class 10, 18.5 kW at 400 V, spring-loaded terminals, for message \"Tripped\".","salesMarkdown":"The Siemens 3RU2126-4PC1 is a SIRIUS S0 thermal overload relay — the part that sits between your contactor and the motor, watching for an overcurrent condition that would cook the windings. It's Class 10, meaning it trips fast enough to protect a standard squirrel-cage motor during a stalled-rotor start, but not so fast that it nuisance-trips on a normal acceleration curve. Rated to switch 18.5 kW at 400 V and handle a maximum of 690 V, so it covers the common European 400 V line and the 690 V industrial bus. The S0 frame size is the compact one — fits into a standard motor starter assembly without eating up DIN rail space. If your motor has a long acceleration time (high-inertia loads like a centrifuge or a crusher drum), you'd step up to Class 20 — but for most line applications, Class 10 is the right call. It's a thermal bimetallic release — old-school, reliable, no electronics to fail in a hot panel. Spring-loaded terminals accept 2x 0.5 to 2.5 mm² solid or stranded. That's the standard control-wiring range; no need for ferrules if you're terminating stranded, though a ferrule makes for a cleaner connection in a vibrating panel. That means this relay can live in an unheated enclosure in a Canadian winter or a Middle Eastern substation shed without derating. The auxiliary contact ratings cover the common control voltages: 2 A at 24 V, 2 A at 230 V, 1 A at 400 V, and 3 A at 120 V. Mounts in any position — horizontal, vertical, upside-down, doesn't matter. Stand-alone installation means it clips directly onto the contactor or onto a DIN rail, no adapter plate needed. Dimensions are 45 mm wide, 114 mm tall, 95 mm deep — fits the S0 footprint. The \"for message 'Tripped'\" note on the relay means it has a mechanical flag or auxiliary contact that signals the tripped state — you don't have to guess whether it's the overload or the contactor that opened the circuit.","metaTitle":"Siemens 3RU2126-4PC1 SIRIUS Thermal Overload Relay, Class 10","metaDescription":"Siemens 3RU2126-4PC1 SIRIUS S0 thermal overload relay, Class 10 protection, 18.5 kW at 400 V. Spring-loaded terminals. Current production. Quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Overload Relays"],"specifications":{"Note":"for message \"Tripped\"","Depth":"95 mm","Width":"45 mm","Height":"114 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":"stand-alone installation","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/3f68b704bc7c484cbfaec2f0df01f3d1.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=159759&mlfb=3RU2126-4PC1","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4PC1/alternatives.json"},"ai":{"faq":[],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU2126-4PC1","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/3RU2126-4PC1 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}}