{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RA2125-1HE24-0FB4","brand":"Siemens","brandSlug":"siemens","productSlug":"3RA2125-1HE24-0FB4","canonicalUrl":"https://aoctrl.com/siemens/3RA2125-1HE24-0FB4","factsUrl":"https://aoctrl.com/api/mcp/products/3RA2125-1HE24-0FB4","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RA2125-1HE24-0FB4 direct online starter, size S0, 3 kW at 400 V AC-3, Class 10, 24 V DC coil, spring-loaded terminals, supplied with contactor and circuit-breaker.","salesMarkdown":"## SIRIUS S0 direct starter — what ships in the box The 3RA2125-1HE24-0FB4 is a Siemens SIRIUS direct online starter, size S0, combining a contactor, thermal overload relay, and short-circuit protection in one assembly. It ships with the 3RT2024-2FB40 contactor and the 3RV2021-1HA25 circuit-breaker pre-configured as a matched set. ## Mounting and wiring — screw or snap-on, spring terminals Mounts on 35 mm DIN rail via screw or snap-on fastening, vertical position only. The S0 footprint is 45 mm wide by 243 mm tall by 107 mm deep — plan for 50 mm clearance above and 20 mm clearance forward for wiring access. Both main power and auxiliary/control circuits terminate with spring-loaded terminals — no screw torque to check, just strip and push in. The 24 V DC coil voltage matches standard control transformer outputs in most panels. ## Overload and short-circuit protection design Thermal (bimetallic) overload release provides inverse-time protection that tracks motor heating. The magnetic short-circuit trip handles fault clearing independently of the thermal element — selectivity with upstream devices depends on the magnetic trip curve of the supplied 3RV2021-1HA25 breaker. Operating ambient range is -20 to +60 °C with 10-95% relative humidity, non-condensing. The temperature compensation keeps the trip curve stable across the band — no manual derating required for most panel environments.","metaTitle":"Siemens 3RA2125-1HE24-0FB4 SIRIUS Direct Starter, S0","metaDescription":"Siemens 3RA2125-1HE24-0FB4 SIRIUS direct online starter, size S0, 3 kW at 400 V AC-3, Class 10. Active production, quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Motor Starters"],"specifications":{"Depth":"107 mm","Width":"45 mm","title":"3RA2125-1HE24-0FB4","Height":"243 mm","Upwards":"50 mm","Forwards":"20 mm","Backwards":"0 mm","Downwards":"10 mm","Trip Class":"CLASS 10","At The Side":"20 mm","Rated Value":"24 ... 24 V","description":"Load feeder fuseless, Direct-on-line starting 400 V AC, Size S0 5.50...8.00 A 24 V DC Spring-type terminal for installation on standard mounting rail (also fulfills type of coordination 1) Type of coordination 2, Iq = 150 kA 1 NO+1 NC (contactor) with diode combination plugged in at the front","During Storage":"-50 ... +80 °C","lifecycle_stage":"current","During Operation":"-20 ... +60 °C","During Transport":"-50 ... +80 °C","Fastening Method":"screw and snap-on mounting onto 35 mm standard mounting rail","Mounting Position":"vertical","PROFIsafe protocol":"No","Product Brand Name":"SIRIUS","Type Of Assignment":"2","Product Designation":"Direct (on-line) starter","Size Of Load Feeder":"S0","PROFINET IO protocol":"No","at 400 V rated value":"3 000 W","Design Of The Product":"for standard rail or screw mounting","For Main Current Circuit":"spring-loaded terminals","Temperature Compensation":"-20 ... +60 °C","Of The Supplied Contactor":"3RT2024-2FB40","Of The Supplied Link Module":"3RA2921-2AA00","Size Of The Circuit-Breaker":"S0","at AC-3 rated value maximum":"690 V","Design Of The Overload Release":"thermal (bimetallic)","Design Of The Switching Contact":"electromechanical","Operating Frequency Rated Value":"50 ... 60 Hz","Design Of The Short-Circuit Trip":"magnetic","Of The Supplied Circuit-Breakers":"3RV2021-1HA25","degree of protection NEMA rating":"other","For Auxiliary And Control Circuit":"spring-loaded terminals","Product Extension Auxiliary Switch":"Yes","Relative Humidity During Operation":"10 ... 95 %","Surge Voltage Resistance Rated Value":"6 kV","Number Of Poles For Main Current Circuit":"3","Product Function Short Circuit Protection":"Yes","protocol is supported AS-Interface protocol":"No","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","shock resistance according to IEC 60068-2-27":"6g / 11 ms","Type Of Voltage Of The Control Supply Voltage":"DC","at 400 V according to IEC 60947-4-1 rated value":"150 000 A","operational current at AC-3 at 400 V rated value":"6.5 A","Mechanical Service Life (Switching Cycles) Of Contactor Typical":"10 000 000","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"5.5 ... 8 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/c9e3150625e2b61a0980a180e84df234.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=552942&mlfb=3RA2125-1HE24-0FB4"},"ai":{"faq":[{"question":"What compliance documentation does Siemens provide for 3RA2125-1HE24-0FB4?","answer":"The starter carries CE marking for the European market. The supplied contactor (3RT2024-2FB40) and circuit-breaker (3RV2021-1HA25) each have their own UL, CSA, and IEC certifications. RoHS and REACH declarations are available from Siemens for the assembly."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RA2125-1HE24-0FB4","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/3RA2125-1HE24-0FB4 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-22T19:47:38.189Z","lastPublished":"2026-07-22T19:47:38.189Z","indexable":true}}