{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RT2028-4XB40-0LA2","brand":"Siemens","brandSlug":"siemens","productSlug":"3RT2028-4XB40-0LA2","canonicalUrl":"https://aoctrl.com/siemens/3RT2028-4XB40-0LA2","factsUrl":"https://aoctrl.com/api/mcp/products/3RT2028-4XB40-0LA2","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS contactor, Size S0, 24 VDC coil, ring cable lug connection, screw and snap-on DIN rail mounting, 3RT2028-4XB40-0LA2.","salesMarkdown":"## SIRIUS Size S0 Contactor with 24 VDC Coil It is rated for a 24 VDC coil with a ring cable lug connection, and it carries an auxiliary switch block integrated into the assembly. The contactor mounts via screw or snap-on onto a 35 mm standard mounting rail per DIN EN 60715, and the mounting position allows +/-180° rotation on a vertical surface with +/-22.5° tilt forward and backward. This flexibility simplifies panel layout when space is tight. Physical envelope is 91 mm high, 45 mm wide, and 107 mm deep — the Size S0 footprint that drops into standard panel cutouts. The auxiliary contacts are rated for DC switching at various voltages: 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, and 2 A at 500 V. At 400 V DC the rating is 3 A, and at 480 V DC it is 34 A — the 480 V figure is the highest DC current rating on the auxiliary side, so it is the one to check for high-voltage DC control circuits. Motor load capability is expressed as 5 hp at 230 V, which gives a quick cross-check against standard North American motor frames. The contactor is rated for 750 switching operations per hour under AC-1, AC-2, AC-3, and AC-3e duty, and 250 operations per hour under AC-4 — the AC-4 figure is the one that governs heavy inrush or plugging applications. The inrush current peak is 3 A at coil pick-up, which is modest enough that most 24 VDC power supplies handle it without derating. ## Environmental and Timing Specifications The DC coil operates at 24 V nominal with a rated value of 24 V and an initial value factor of 0.7, meaning the coil must see at least 16.8 V to pull in reliably. Timing is tight: the DC operate time is 30 to 50 ms, and arcing time is 10 ms. These numbers matter when coordinating with upstream protection devices or sequencing multiple contactors in a motor control center. Because it is a current-production Siemens SIRIUS part, lead times are predictable through the authorized channel, and the ring cable lug coil connection is a standard variant that does not require special factory programming.","metaTitle":"Siemens 3RT2028-4XB40-0LA2 SIRIUS Contactor, 24 VDC, Size S0","metaDescription":"Siemens SIRIUS 3RT2028-4XB40-0LA2 contactor, 24 VDC coil, Size S0 frame. Active production. Screw and snap-on DIN rail mount. Rated for motor loads up to 5 hp at 230 V. Sourced to","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Contactors"],"specifications":{"Depth":"107 mm","Width":"45 mm","at DC":"30 ... 50 ms","Height":"91 mm","Upwards":"10 mm","Forwards":"10 mm","Downwards":"10 mm","Arcing Time":"10 ... 10 ms","At The Side":"6 mm","Rated Value":"24 V","Initial Value":"0.7","During Storage":"-55 ... +80 °C","Of Magnet Coil":"Ring cable lug connection","Type Of Voltage":"DC","at AC-1 maximum":"750 1/h","at AC-2 maximum":"750 1/h","at AC-3 maximum":"750 1/h","at AC-4 maximum":"250 1/h","lifecycle_stage":"current","Auxiliary Switch":"Yes","During Operation":"-40 ... +70 °C","Fastening Method":"screw and snap-on mounting onto 35 mm standard mounting rail according to DIN EN 60715","Full-Scale Value":"1.25","at AC-3e maximum":"750 1/h","Mounting Position":"+/-180° rotation possible on vertical mounting surface; can be tilted forward and backward by +/- 22.5° on vertical mounting surface","Size Of Contactor":"S0","Product Brand Name":"SIRIUS","Inrush Current Peak":"3 A","Product Designation":"Contactor","at 24 V rated value":"10 A","at 48 V rated value":"2 A","at 60 V rated value":"2 A","Of Contactor Typical":"10 000 000","at 110 V rated value":"1 A","at 125 V rated value":"0.9 A","at 220 V rated value":"0.3 A","at 230 V rated value":"5 hp","at 400 V rated value":"3 A","at 480 V rated value":"34 A","at 500 V rated value":"2 A","at 600 V rated value":"27 A","at 690 V rated value":"1 A","Design Of The Product":"With extended operating range","Instantaneous Contact":"1","Side-By-Side Mounting":"Yes","For Main Current Circuit":"Ring cable lug connection","at 110/120 V rated value":"3 hp","at 200/208 V rated value":"10 hp","at 220/230 V rated value":"10 hp","at 460/480 V rated value":"25 hp","at 575/600 V rated value":"25 hp","at AC-2 at AC-3e maximum":"750 1/h","Locked-Rotor Current Peak":"0.52 A","Relative Humidity Minimum":"10 %","Holding Current Mean Value":"45 mA","at maximum Ith rated value":"10 mm²","Of Main Circuit Rated Value":"6 kV","at AC-3 rated value maximum":"690 V","at maximum AC-1 rated value":"10 mm²","at AC in hot operating state":"11.4 W","at AC-2 at 400 V rated value":"18.5 kW","at AC-3e rated value maximum":"690 V","at AC-4 at 400 V rated value":"22 A","Substance Prohibitance (Date)":"10/01/2009","Design Of The Surge Suppressor":"with varistor","Duration Of Inrush Current Peak":"30 µs","Locked-Rotor Current Mean Value":"0.3 A","Duration Of Locked-Rotor Current":"180 ms","Of Auxiliary Circuit Rated Value":"6 kV","For Auxiliary And Control Circuit":"ring terminal lug connection","Function Module For Communication":"No","Product Function Bus Communication":"No","With Type Of Assignment 2 Required":"gG: 50A (690V,100kA), aM: 25A (690V, 100kA), BS88: 50A (415V, 80kA)","Without Load Current Share Typical":"0.8 W","closing power of magnet coil at DC":"6.7 W","holding power of magnet coil at DC":"1.4 W","At Contactor For Auxiliary Contacts":"Ring cable lug connection","With Type Of Coordination 1 Required":"gG: 125A (690V,100kA), aM: 50A (690V,100kA), BS88: 125A (415V,80kA)","operational current at AC-12 maximum":"10 A","at AC in hot operating state per pole":"3.8 W","number of NO contacts for main contacts":"3","reference code according to IEC 81346-2":"Q","Number Of Poles For Main Current Circuit":"3","Product Function Short Circuit Protection":"No","mirror contact according to IEC 60947-4-1":"Yes","with low demand rate according to SN 31920":"40 %","with high demand rate according to SN 31920":"73 %","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","Type Of Voltage Of The Control Supply Voltage":"DC","up to 40 °C according to IEC 60077 rated value":"50 A","up to 70 °C according to IEC 60077 rated value":"38 A","Limited To 1 S Switching At Zero Current Maximum":"593 A; Use minimum cross-section acc. to AC-1 rated value","Limited To 5 S Switching At Zero Current Maximum":"395 A; Use minimum cross-section acc. to AC-1 rated value","Limited To 10 S Switching At Zero Current Maximum":"260 A; Use minimum cross-section acc. to AC-1 rated value","Limited To 30 S Switching At Zero Current Maximum":"186 A; Use minimum cross-section acc. to AC-1 rated value","Limited To 60 S Switching At Zero Current Maximum":"152 A; Use minimum cross-section acc. to AC-1 rated value","contact rating of auxiliary contacts according to UL":"A600 / Q600","Of Main Circuit With Degree Of Pollution 3 Rated Value":"690 V","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Of The Contactor With Added Auxiliary Switch Block Typical":"10 000 000","Of Auxiliary Circuit With Degree Of Pollution 3 Rated Value":"690 V","For Short-Circuit Protection Of The Auxiliary Switch Required":"gG: 10 A (500 V, 1 kA)","Of The Contactor With Added Electronically Optimized Auxiliary Switch Block Typical":"5 000 000"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/d346301cbef8a63af8f3d131245897f7.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=335594&mlfb=3RT2028-4XB40-0LA2","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RT2028-4XB40-0LA2/alternatives.json"},"ai":{"faq":[{"question":"What is the closest functional second-source to the 3RT2028-4XB40-0LA2?","answer":"The 3RT2028-1BB40 is a peer in the same Size S0 frame, but it uses a 24 VAC/DC coil with a different termination style (screw terminal vs ring cable lug). The 3RT2028-4XB40-0LA2 has the ring cable lug connection, so a panel wired for screw terminals would need adapter lugs or a terminal block change to accept the ring lug. The 3RT2028-1BB44-3MA0 is another Size S0 variant with a 24 VDC coil but with a different auxiliary contact configuration. Check the auxiliary contact count and coil termination before substituting."},{"question":"What are the key dimensions of the 3RT2028-4XB40-0LA2?","answer":"Height is 91 mm, width is 45 mm, and depth is 107 mm. Clearance distances are 10 mm upwards, forwards, and downwards, and 6 mm at the side."},{"question":"Will the 3RT2028-4XB40-0LA2 drop into a panel specified around the 3RT2028-1BB40 without rewiring?","answer":"The physical footprint is the same Size S0 (91 x 45 x 107 mm), so it fits the same DIN rail cutout and mounting holes. However, the 3RT2028-4XB40-0LA2 uses a ring cable lug connection for the coil, while the 3RT2028-1BB40 uses screw terminals. If the panel wiring is terminated with ring lugs, it is a direct swap; if the wiring uses bare wires or ferrules for screw terminals, you will need to add ring lugs or replace the contactor with the screw-terminal variant."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RT2028-4XB40-0LA2","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/3RT2028-4XB40-0LA2 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}}