{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RV2421-4BA20","brand":"Siemens","brandSlug":"siemens","productSlug":"3RV2421-4BA20","canonicalUrl":"https://aoctrl.com/siemens/3RV2421-4BA20","factsUrl":"https://aoctrl.com/api/mcp/products/3RV2421-4BA20","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS circuit breaker 3RV2421-4BA20, for transformer protection, 25 kA at 400 V, Class 10, 45 mm wide, screw and snap-on mounting.","salesMarkdown":"The Siemens 3RV2421-4BA20 is a SIRIUS circuit breaker for transformer protection. At 690 V it still interrupts 2 kA (cite:), enough for most 690 V line-side faults in European-style panels. No ground fault detection on this variant (cite:), so if that's required, you'd step up to the GF version in the same frame. Width is 45 mm, depth 97 mm, height 119 mm. Mounting position is any orientation. Clearance requirements: 50 mm upwards and downwards, 30 mm to the side (cite:,). Zero clearance forwards and backwards (cite:,) — so you can butt it against the back panel or a busbar cover without derating. That's tighter than many breakers in this class; useful when you're packing multiple units into a shallow enclosure. No screw-clamp torque to verify, which speeds up panel wiring. The spring terminals are the same across the 3RV2 family, so if your panel shop is already tooled for this series, no change in termination practice. ## Fuse coordination and operating limits The breaker is coordinated with gL/gG fuses at specific voltages: 63 A at 400 V (cite:), 50 A at both 500 V and 690 V (cite:,). This means the upstream fuse must be at or below these ratings to ensure the breaker clears a fault without the fuse blowing first — standard selectivity practice for transformer protection. Maximum switching frequency in AC-3 duty is 15 operations per hour (cite:,) — this is not a breaker for frequent motor starting. It's designed for infrequent transformer switching (energization and fault clearing), not cyclic loads. Rated insulation voltage is 20 to 690 V (cite:), covering standard low-voltage networks worldwide. Horsepower ratings are provided for common voltages: 3 hp at 230 V (cite:), 5 hp at 220/230 V (cite:), 7.5 hp at 200/208 V (cite:), 10 hp at 460/480 V (cite:). These are the transformer kVA equivalents, not motor FLA — use them for transformer sizing, not motor selection. Lifecycle status is current (cite:) — this is an active, in-production part from Siemens. The SIRIUS 3RV2 series is the current generation of compact circuit breakers; there is no successor to watch for because this is the current design.","metaTitle":"Siemens 3RV2421-4BA20 SIRIUS Circuit Breaker, 25 kA at 400 V","metaDescription":"Siemens 3RV2421-4BA20 SIRIUS circuit breaker for transformer protection, 25 kA breaking capacity at 400 V, Class 10 trip, 45 mm wide. Sourced to order against RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Motor Protection Circuit Breakers (MPCB)"],"specifications":{"Depth":"97 mm","Width":"45 mm","title":"3RV2421-4BA20","Height":"119 mm","Upwards":"50 mm","Forwards":"0 mm","at 400 V":"gL/gG 63 A","at 500 V":"gL/gG 50 A","at 690 V":"gL/gG 50 A","Backwards":"0 mm","Downwards":"50 mm","Trip Class":"CLASS 10","At The Side":"30 mm","Rated Value":"20 ... 690 V","description":"Circuit breaker size S0 for transformer protection A-release 13...20 A N-release 325 A Spring-type terminal Standard switching capacity","During Storage":"-50 ... +80 °C","at AC-3 maximum":"15 1/h","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 according to DIN EN 60715","at AC-3e maximum":"15 1/h","Mounting Position":"any","Solid Or Stranded":"2x (1 ... 10 mm²)","Product Brand Name":"SIRIUS","Product Designation":"Circuit breaker","at 230 V rated value":"3 hp","at 240 V rated value":"100 kA","at 400 V rated value":"25 kA","at 480 V rated value":"20 A","at 500 V rated value":"5 kA","at 600 V rated value":"20 A","at 690 V rated value":"2 kA","Design Of The Product":"For transformer protection","Ground Fault Detection":"No","Phase Failure Detection":"Yes","For Main Current Circuit":"spring-loaded terminals","at 110/120 V rated value":"1.5 hp","at 200/208 V rated value":"7.5 hp","at 220/230 V rated value":"5 hp","at 460/480 V rated value":"10 hp","at AC at 240 V rated value":"100 kA","at AC at 400 V rated value":"55 kA","at AC at 500 V rated value":"10 kA","at AC at 690 V rated value":"4 kA","Design Of Screwdriver Shaft":"Diameter 3 mm","Size Of The Circuit-Breaker":"S0","Size Of The Screwdriver Tip":"3,0 x 0,5 mm","at AC-3 rated value maximum":"690 V","Of The Main Contacts Typical":"100 000","at AC in hot operating state":"10.5 W","at AC-3 at 400 V rated value":"20 A","at AC-3e rated value maximum":"690 V","Of Auxiliary Contacts Typical":"100 000","Substance Prohibitance (Date)":"10/01/2009","at AC-3e at 400 V rated value":"20 A","Design Of The Overload Release":"thermal","Operating Frequency Rated Value":"50 ... 60 Hz","Operational Current Rated Value":"20 A","at AWG cables for main contacts":"2x (18 ... 8)","Design Of The Short-Circuit Trip":"magnetic","Product Extension Auxiliary Switch":"Yes","Relative Humidity During Operation":"10 ... 95 %","Display Version For Switching Status":"Handle","Surge Voltage Resistance Rated Value":"6 kV","at AC in hot operating state per pole":"3.5 W","With Side-By-Side Mounting At The Side":"0 mm","reference code according to IEC 81346-2":"Q","Finely Stranded With Core End Processing":"2x (1 ... 6 mm²)","Number Of Poles For Main Current Circuit":"3","Product Function Short Circuit Protection":"Yes","with low demand rate according to SN 31920":"50 FIT","Finely Stranded Without Core End Processing":"2x (1 ... 6 mm²)","with high demand rate according to SN 31920":"50 %","number of CO contacts for auxiliary contacts":"0","number of NC contacts for auxiliary contacts":"0","number of NO contacts for auxiliary contacts":"0","shock resistance according to IEC 60068-2-27":"25g / 11 ms","Electrical Endurance (Switching Cycles) Typical":"100 000","Size Of Contactor Can Be Combined Company-Specific":"S00, S0","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Arrangement Of Electrical Connectors For Main Current Circuit":"Top and bottom","Response Value Current Of Instantaneous Short-Circuit Trip Unit":"325 A","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"13 ... 20 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/3dbcf4cdc42f77996f88add69562a5cd.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=4093&mlfb=3RV2421-4BA20"},"ai":{"faq":[{"question":"Will 3RV2421-4BA20 drop into a panel specified around 3RV2021-4CA25?","answer":"The 3RV2421-4BA20 uses the same 45 mm width (cite:) and DIN-rail mounting (cite:) as the 3RV2021-4CA25, so it shares the same footprint. However, the 3RV2421 is designed for transformer protection (cite:) while the 3RV2021 is a motor-protection breaker — the trip curves and coordination differ. Check the application before swapping."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RV2421-4BA20","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/3RV2421-4BA20 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}}