{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-1CB41-1AA0","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-1CB41-1AA0","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-1CB41-1AA0","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1CB41-1AA0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-1CB41-1AA0 safety relay, 24 VDC, SIL 3 / PL e, 3 A switching capacity, screw terminals, 22.5 mm width.","salesMarkdown":"The Siemens 3SK1121-1CB41-1AA0 is a SIRIUS safety relay rated for 24 VDC control voltage, with SIL 3 (IEC 61508 / IEC 62061) and PL e (ISO 13849-1) capability — the highest integrity tier for guarding hazardous machinery. It switches loads up to 3 A at 24 V, 115 V, or 230 V, so it handles solenoid valves, contactor coils, and indicator lamps directly without an interposing relay. The 22.5 mm wide housing snaps onto DIN rail (screw and snap-on mounting) and accepts screw-type terminals for 0.5–2.5 mm² conductors. ## Safety integrity and monitoring features With a safe failure fraction of 99 % and a maximum operating frequency of 360 cycles per hour, this relay suits high-demand safety applications like press guarding, robot cell access gates, and conveyor emergency stops. It includes a start input, feedback input, and monitoring of floating sensors — all required for a Category 4 / PL e safety circuit. The sensor input minimum pulse duration is 75 ms, which filters out contact bounce from mechanical safety switches. Cascading is supported, so multiple 3SK1121 units can chain together for zone control without extra logic. ## Thermal derating and environmental limits Total current through the relay drops from 12 A at 40 °C to 6 A at 60 °C — a straight 50 % derating curve that matters when packing multiple units in a closed panel. Shock resistance is 10 g for 11 ms, typical for machine-mounted enclosures. Power dissipation is 2.5 W maximum. Mounting position is any orientation, but the derating must be observed when units are side-by-side without air gap.","metaTitle":"Siemens 3SK1121-1CB41-1AA0 Safety Relay, SIL 3/PL e, 24 VDC","metaDescription":"Siemens 3SK1121-1CB41-1AA0 safety relay, 24 VDC, SIL 3 / PL e, 3 A contacts, screw terminals. Active production. Quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Safety Relays"],"specifications":{"Depth":"121.6 mm","Solid":"1x (20 ... 14), 2x (18 ... 16)","Width":"22.5 mm","at DC":"0.8 ... 1.2","Height":"100 mm","Maximum":"40 ms","Typical":"30 ms","at 24 V":"3 A","Stranded":"1x (20 ... 16), 2x (20 ... 16)","at 115 V":"3 A","at 230 V":"3 A","Rated Value":"24 V","Start Input":"Yes","Safety Switch":"Yes","at DC maximum":"110 ms","During Storage":"-40 ... +80 °C","Feedback Input":"Yes","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting","Shock Resistance":"10g / 11 ms","Mounting Position":"any (observe derating)","Degree Of Pollution":"3","Overvoltage Category":"3","according to IEC 61508":"3","according to IEC 62061":"3","power loss [W] maximum":"2.5 W","Design Of The Cascading":"yes","Safety-Related Circuits":"Yes","EMC emitted interference":"IEC 60947-5-1, Class A","With Core End Processing":"1x (0.5 ... 2.5 mm²), 2x (0.5 ... 1.0 mm²)","according to ISO 13849-1":"e","Of The Sensor Input Minimum":"75 ms","Operating Frequency Maximum":"360 1/h","Safe failure fraction (SFF)":"99 %","Type Of Electrical Connection":"screw-type terminals","Insulation Voltage Rated Value":"300 V","Monitoring Of Floating Sensors":"Yes","total current at 40 °C maximum":"12 A","total current at 60 °C maximum":"6 A","Product Function Parameterizable":"sensor floating / sensor non-floating, monitored start-up / automatic start, 1-channel / 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, 2-hand switches, time delay","Safety-Related Delayed Switching":"2","Monitoring Of Non-Floating Sensors":"Yes","Relative Humidity During Operation":"10 ... 95 %","air pressure according to SN 31205":"90 ... 106 kPa","of the ON pushbutton input minimum":"0.15 s","Product Feature Cross-Circuit-Proof":"Yes","operational current at 17 V minimum":"5 mA","Cascading Input/Functional Switching":"Yes","Safety-Related Instantaneous Contact":"2","Surge Voltage Resistance Rated Value":"4 000 V","category according to EN ISO 13849-1":"4","protection class IP of the enclosure":"IP20","stop category according to EN 60204-1":"0 / 1","installation environment regarding EMC":"This product is suitable for Class A environments only. In household environments, this device can cause unwanted radio interference. The user is required to implement appropriate measures in this case.","Magnetically Operated Switch Monitoring":"Yes","reference code according to IEC 81346-2":"F","Recovery Time After Power Failure Typical":"6.5 s","Suitability For Interaction Press Control":"Yes","Touch Protection Against Electrical Shock":"finger-safe","safety device type according to IEC 61508-2":"Type B","Type Of Electrical Connection Plug-In Socket":"No","Type Of Voltage Of The Control Supply Voltage":"DC","Number Of Sensor Inputs 1-Channel Or 2-Channel":"1","Required Spacing For Grounded Parts At The Side":"5 mm","Type Of The Safety-Related Wiring Of The Inputs":"single-channel and two-channel","hardware fault tolerance according to IEC 61508":"1","vibration resistance according to IEC 60068-2-6":"5 ... 500 Hz: 0.75 mm","PFHD with high demand rate according to EN 62061":"3.7E-9 1/h","suitability for operation device connector 3ZY12":"Yes","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","PFDavg with low demand rate according to IEC 61508":"7E-6","for delayed release circuit according to IEC 61508":"SIL3","Installation Altitude At Height Above Sea Level Maximum":"4 000 m; Derating, see Product Notification 109792701","Recovery Time After Opening Of The Safety Circuits Typical":"30 ms","adjustable OFF-delay time after opening of the safety circuits":"0.05 ... 3","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms","thermal current of the switching element with contacts at 40 °C maximum":"5 A","thermal current of the switching element with contacts at 60 °C maximum":"2 A","design of the fuse link for short-circuit protection of the NO contacts of the relay outputs required":"gL/gG: 6A or circuit breaker type A: 3A or circuit breaker type B: 2A or circuit breaker type C: 1A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1CB41-1AA0/alternatives.json"},"ai":{"faq":[{"question":"What safety integrity levels does 3SK1121-1CB41-1AA0 meet?","answer":"It meets SIL 3 per IEC 61508 and IEC 62061, and PL e per ISO 13849-1 — the highest functional safety level for most industrial machinery."},{"question":"What are the contact ratings on this safety relay?","answer":"Switching capacity is 3 A at 24 V DC, 115 V AC, and 230 V AC — sufficient for direct control of contactor coils and solenoid valves without an interposing relay."},{"question":"What is the depth of 3SK1121-1CB41-1AA0?","answer":"The depth is 121.6 mm, width is 22.5 mm, and height is 100 mm — a standard 22.5 mm modular safety relay footprint for DIN rail mounting."},{"question":"Where can I buy 3SK1121-1CB41-1AA0 and how is it quoted?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time."},{"question":"Does 3SK1121-1CB41-1AA0 support cascading?","answer":"Yes, cascading is supported, allowing multiple units to be linked for zone-based safety monitoring without additional logic modules."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-1CB41-1AA0","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/3SK1121-1CB41-1AA0 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}}