{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"5SJ4303-7HG42","brand":"Siemens","brandSlug":"siemens","productSlug":"5SJ4303-7HG42","canonicalUrl":"https://aoctrl.com/siemens/5SJ4303-7HG42","factsUrl":"https://aoctrl.com/api/mcp/products/5SJ4303-7HG42","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 5SJ4 series, miniature circuit breaker 5SJ4303-7HG42, 3-pole, 3 A rated at 30/40 °C, DIN rail mount, IP20/IP40.","salesMarkdown":"## Siemens 5SJ4303-7HG42 — 3 A, 3-Pole MCB for DIN-Rail Panels The Siemens 5SJ4303-7HG42 is a 3-pole miniature circuit breaker from the SENTRON 5SJ4 series, rated at 3 A at both 30 °C and 40 °C ambient. The 3 A rating holds steady up to 40 °C, then derates linearly to 2.6 A at 60 °C — a curve worth checking if the breaker sits near transformers or other heat sources inside a sealed enclosure. The 70 mm depth (installation depth also 70 mm) keeps it flush with standard busbar systems and terminal blocks on the same rail. ## Thermal Performance and Derating Rated current is 3 A at 30 °C and 40 °C, dropping to 2.9 A at 45 °C, 2.8 A at 50 °C, 2.7 A at 55 °C, and 2.6 A at 60 °C. This derating profile means the breaker's real-world capacity in a warm panel is lower than the nameplate 3 A — factor the ambient temperature into your load calculation. The 75 °C maximum covers internal heating from the load plus ambient; the -40 °C floor suits unheated warehouses or outdoor enclosures in cold climates. Protection class is IP20 with conductors connected, IP40 in the handle range — suitable for enclosed panels where accidental contact is prevented. The breaker is sealable, allowing lockout/tagout provisions on the handle. Vibration resistance is 50 m/s² at 25–150 Hz and 60 m/s² at 35 Hz (4 s), adequate for machine-mounted subpanels. ## DC Rating and Application Notes Maximum DC rated voltage is 60 V. This is a thermal-magnetic MCB designed primarily for AC circuits (per EN 60898 / IEC 60947-2), but the DC rating allows use in 24 V or 48 V control circuits — though verify the DC breaking capacity against your fault current. The 3-pole design (3P) does not switch the neutral; neutral conductor switching is not provided.","metaTitle":"Siemens 5SJ4303-7HG42 SENTRON MCB, 3-Pole 3 A, DIN Rail","metaDescription":"Siemens 5SJ4303-7HG42 SENTRON miniature circuit breaker, 3-pole, 3 A rated, DIN rail mount. IP20/IP40. Sourced to order against RFQ. Available now.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["3-Pole MCB (DIN Rail)"],"specifications":{"Depth":"70 mm","Width":"54 mm","title":"5SJ4303-7HG42","Height":"121 mm","Maximum":"75 °C","Minimum":"-40 °C","Sealable":"Yes","description":"Circuit breaker 10kA, 3-pole, C, 3 A according to UL 489-480Y/277V","Halogen-Free":"Yes","Silicon-Free":"Yes","Design Of Pole":"3P","Number Of Poles":"3","lifecycle_stage":"current","Fastening Method":"on standard mounting rail","Mounting Position":"any","at AC rated value":"3 A","Installation Depth":"70 mm","Product Brand Name":"SENTRON","Degree Of Pollution":"3","Product Designation":"Miniature circuit breakers","protection class IP":"IP20, with connected conductors, IP 40 in the handle range","Overvoltage Category":"3","Tunnel Terminals Top":"No","Vibration Resistance":"50 m/s² at 25 to 150Hz and 60m/s² at 35Hz (4sec)","Combined Terminal Top":"Yes","Design Of The Product":"Miniature circuit-breaker 5SJ4","Product Function Note":"Terminal tightening torque for Cu, 60/75°C; 3.5Nm/31lb.in","at 30 °C rated value":"3 A","at 40 °C rated value":"3 A","at 45 °C rated value":"2.9 A","at 50 °C rated value":"2.8 A","at 55 °C rated value":"2.7 A","at 60 °C rated value":"2.6 A","Tunnel Terminals Bottom":"No","according to EN 61346-2":"F","Combined Terminal Bottom":"Yes","according to IEC 81346-2":"F","Suitability For Operation":"Mechanical engineering / industry","at DC rated value maximum":"60 V","Neutral Conductor Switching":"No","Number Of Modular Width Units":"3","Position Of Power Supply Cord":"Any","Tripping Characteristic Class":"C","supply voltage at AC rated value":"400 V","according to EN 60898 rated value":"10 kA","Ambient Temperature During Operation":"max. 95% humidity","Supply Voltage Frequency Rated Value":"50 Hz","according to IEC 60947-2 rated value":"15 kA","installation environment regarding EMC":"Suitable for environment B (immunity to interference not applicable)","Type Of Voltage Of The Operating Voltage":"AC/DC","insulation voltage (Ui) at AC rated value":"440 V","Value Range Of The Supply Voltage Frequency":"50/60 Hz","vibration resistance according to IEC 60068-2-6":"±1 mm at 5 to 25 Hz; 50 m/s² at 25 to 150 Hz","Mechanical Service Life (Operating Cycles) Typical":"10 000","Product Extension Installable Supplementary Devices":"Yes","Tightening Torque With Screw-Type Terminals Maximum":"3.5 N·m","power loss [W] for rated value of the current at AC in hot operating state per pole":"1.8 W"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/99775cf479ac80b654836c36700729f6.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=368384&mlfb=5SJ4303-7HG42"},"ai":{"faq":[{"question":"What is the closest functional second-source to the 5SJ4303-7HG42?","answer":"The Siemens 5SY4304-7CV is a 3-pole MCB with a 4 A rating (one step higher) in the same 5SY family. It shares the same 3-module width (54 mm) and DIN-rail mounting, so it can drop into the same panel footprint. However, the 5SJ4303-7HG42 is rated at 3 A, so the 5SY4304-7CV would require a load-side ampacity check before substitution."},{"question":"Where can I buy the 5SJ4303-7HG42?","answer":"This part is sourced and quoted to order against an RFQ through independent industrial-automation distribution. Submit an RFQ for current availability and pricing; no stock count or lead-time figure is listed here."},{"question":"What are the key dimensions of the 5SJ4303-7HG42?","answer":"Depth is 70 mm, width is 54 mm (3 modular units), and height is 121 mm. Installation depth matches the 70 mm depth."},{"question":"Will the 5SJ4303-7HG42 fit a panel designed for the 5SY4304-7CV?","answer":"Yes — both breakers share the same 54 mm width (3 MW), 70 mm depth, and DIN-rail mounting. The 5SJ4303-7HG42 will physically drop into the same panel position without rewiring the busbar or terminal layout. The difference is the amp rating: 3 A vs 4 A."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/5SJ4303-7HG42","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/5SJ4303-7HG42 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}