{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RU2126-4AC0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RU2126-4AC0","canonicalUrl":"https://aoctrl.com/siemens/3RU2126-4AC0","factsUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4AC0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS thermal overload relay, 3RU2126-4AC0, size S0, Trip Class 10, rated 690 V, 7.5 kW at 400 V, spring-loaded terminals.","salesMarkdown":"The Siemens 3RU2126-4AC0 is a SIRIUS thermal overload relay — size S0, Trip Class 10 — designed to protect motors against sustained overcurrent by monitoring the current draw and tripping the associated contactor when the thermal model exceeds the threshold. Class 10 means it must trip within 10 seconds at 7.2× the current setting, which is the standard for standard-duty induction motors that don't need the extended start time of Class 20 or 30 — common for pumps, fans, and compressors on a general-purpose line. Rated for a maximum of 690 V, the relay carries a 7.5 kW motor at 400 V and 11 kW at 690 V, so the same unit covers both 400 V and 690 V networks without a change in hardware — just the setting dial. Mounts directly onto the contactor via the fastening method — no DIN rail required, which saves a rail slot and keeps the motor starter assembly compact. Any mounting position is permitted, so panel layout is flexible. The main current circuit uses spring-loaded terminals, accepting 2 × 0.5 to 2.5 mm² solid or stranded wire. No screw torque to verify — just strip to 8 mm and push in. The auxiliary switch is integrated, so no separate block to order for the trip signal. Dimensions are 45 mm wide, 102 mm high, 84 mm deep — size S0 footprint. MTTF at high demand rate is 2 280 years — a reliability figure that reflects the passive thermal design with no moving electronics to fail. Substance prohibition date of 10/01/2009 indicates RoHS compliance by that date.","metaTitle":"Siemens 3RU2126-4AC0 SIRIUS thermal overload relay, S0, Clas","metaDescription":"Siemens 3RU2126-4AC0 SIRIUS thermal overload relay, size S0, Trip Class 10, rated 690 V, 7.5 kW at 400 V. Current production. Spring-loaded terminals. RFQ for lead time.","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":"16 A","at 500 V rated value":"7.5 kW","at 600 V rated value":"16 A","at 690 V rated value":"11 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":"16 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":"16 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":"11 ... 16 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$30.48","priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/981aaac1661cd738167ffc1d2ad81633.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=107086&mlfb=3RU2126-4AC0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RU2126-4AC0/alternatives.json"},"ai":{"faq":[{"question":"What does the note 'for message Tripped' mean?","answer":"It refers to the integrated auxiliary switch that changes state when the thermal overload relay trips, providing a signal (typically an N/C contact opening) to a PLC input or panel indicator that the motor has been disconnected due to overload."},{"question":"What is the depth of the 3RU2126-4AC0?","answer":"84 mm depth, with a width of 45 mm and height of 102 mm — size S0 footprint that mounts directly onto the contactor."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RU2126-4AC0","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/3RU2126-4AC0 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}}