{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2055-2FC2","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2055-2FC2","canonicalUrl":"https://aoctrl.com/siemens/3RB2055-2FC2","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2055-2FC2","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2055-2FC2, CLASS 20E, 120 x 119 x 155 mm, contactor mounting/stand-alone, IP00, ATEX Ex II (2) GD.","salesMarkdown":"The Siemens SIRIUS 3RB2055-2FC2 is a solid-state overload relay, part of the SIRIUS family, designed to protect motors and other loads against prolonged overcurrent conditions. It uses a CLASS 20E trip curve, meaning it allows a 20-second trip time at 7.2x the current setting — standard for moderate-inertia loads like pumps and compressors. The relay mounts either directly onto a contactor or standalone on a DIN rail, giving the panel builder flexibility in layout. Rated for a maximum operating voltage of 1 000 V AC-3 and with a surge voltage resistance of 8 kV, it fits into 400 V and 690 V industrial networks without additional surge suppression for most installations. The CLASS 20E trip class is the headline rating: it defines how fast the relay opens on a severe overload. For a motor starting a high-inertia fan, a CLASS 20E relay gives enough time for the inrush to decay without nuisance tripping, while still protecting the motor from sustained overcurrents. The relay's solid-state design means no heating elements to age or drift, and the power dissipation per pole is only 0.02 W in hot operating state — negligible for panel thermal budget. The auxiliary contact ratings cover common control voltages: 4 A at 120 V AC, 3 A at 230 V AC, and 2 A at 24 V DC — enough to switch a PLC input or a small contactor coil directly. The relay carries ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD), so it can be installed in the safe area of a zone 2 gas or zone 22 dust hazardous location, protecting motors in the hazardous zone. This is a key differentiator for petrochemical and grain-handling applications where standard overload relays cannot be used. ## Mechanical and environmental integration The front face is IP00 (no protection against dust ingress), so it must be installed inside an enclosure with at least IP54 to keep the terminals clean. Side clearance to adjacent devices is 6 mm, which is tight enough for dense panels. Wire range accepts solid conductors from 0.5 to 4 mm², and with ferrule processing from 0.5 to 2.5 mm² — covers standard motor-circuit wiring. The main current circuit uses busbar connection, not screw terminals, so plan for busbar taps rather than ring lugs. Operating temperature range is -25 to +60 °C, storage and transport range is -40 to +80 °C, and it withstands 100 % relative humidity — suitable for unconditioned electrical rooms in most climates.","metaTitle":"Siemens SIRIUS 3RB2055-2FC2 solid-state overload relay, CLAS","metaDescription":"Siemens SIRIUS 3RB2055-2FC2 solid-state overload relay, CLASS 20E trip class, 120x119x155 mm, contactor mounting or standalone, IP00, ATEX, active production.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"155 mm","Solid":"0.5 ... 4 mm², 2x (0.5 ... 2.5 mm²)","Width":"120 mm","Height":"119 mm","Maximum":"2 000 m","Upwards":"0 mm","at 24 V":"2 A","at 60 V":"0.55 A","Forwards":"0 mm","at 110 V":"0.3 A","at 120 V":"4 A","at 125 V":"0.3 A","at 220 V":"0.11 A","at 230 V":"3 A","Backwards":"0 mm","Downwards":"0 mm","Trip class":"CLASS 20E","At The Side":"6 mm","On The Front":"IP00","Mounting type":"Contactor mounting/stand-alone installation","During Storage":"-40 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","Shock resistance":"15g / 11 ms","Mounting position":"any","Product brand name":"SIRIUS","Type of protection":"PTB 06 ATEX 3001 Ex II (2) GD","Product designation":"solid-state overload relay","For Auxiliary Contacts":"0","For Main Current Circuit":"busbar connection","at AC-3 rated value maximum":"1 000 V","at AC in hot operating state":"0.05 W","Relative humidity during operation":"100 %","due to burst acc. to IEC 61000-4-4":"2 kV (power ports), 1 kV (signal ports) corresponds to degree of severity 3","Surge voltage resistance rated value":"8 kV","Reference code acc. to DIN EN 81346-2":"F","at AC in hot operating state per pole":"0.02 W","With Degree Of Pollution 3 Rated Value":"1 000 V","Finely Stranded With Core End Processing":"0.5 ... 2.5 mm², 2x (0.5 ... 1.5 mm²)","Number of poles for main current circuit":"3","at AWG conductors for auxiliary contacts":"2x (20 ... 14)","For Auxiliary And Control Current Circuit":"screw-type terminals","Number of NC contacts for auxiliary contacts":"1","Number of NO contacts for auxiliary contacts":"1","Electrostatic discharge acc. to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Size of contactor can be combined company-specific":"S6","due to conductor-earth surge acc. to IEC 61000-4-5":"2 kV (line to earth) corresponds to degree of severity 3","Removable Terminal For Auxiliary And Control Circuit":"Yes","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 6 A","Adjustable pick-up value current of the current-dependent overload release":"50 ... 200 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=500703&mlfb=3RB2055-2FC2","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2055-2FC2/alternatives.json"},"ai":{"faq":[{"question":"What are the key ratings for this overload relay?","answer":"CLASS 20E trip curve, maximum operating voltage 1 000 V AC-3, surge voltage resistance 8 kV, auxiliary contact ratings of 4 A at 120 V AC and 2 A at 24 V DC, and ATEX Ex II (2) GD approval."},{"question":"What is the depth of the 3RB2055-2FC2?","answer":"The depth is 155 mm."},{"question":"What wire sizes does it accept?","answer":"Solid conductors from 0.5 to 4 mm², and with ferrule processing from 0.5 to 2.5 mm²."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2055-2FC2","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/3RB2055-2FC2 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}}