{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-1CB44","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-1CB44","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-1CB44","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1CB44","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-1CB44 safety relay, 24 V DC, 3 A contacts, SIL 3 / PL e, 22.5 mm wide, screw and snap-on mounting.","salesMarkdown":"## Safety relay for enabling circuits — 22.5 mm wide, SIL 3 / PL e The Siemens SIRIUS 3SK1121-1CB44 is a safety relay for relay enabling circuits, with a safe failure fraction of 99 %. SIL 3 / PL e is the highest integrity level for single-channel safety relays under these standards — it means the relay can be used in safety functions up to Category 4 architecture, suitable for guarding hazard zones on machinery where a failure could cause serious injury. The 99 % safe failure fraction (SFF) indicates that 99 % of possible dangerous failures are detected or are inherently safe. Response time is 30 ms typical, 40 ms maximum, with a DC maximum of 110 ms — fast enough for most emergency-stop and light-curtain applications, but verify against your safety distance calculation if the stopping time is critical. The sensor input minimum pulse duration of 75 ms and maximum operating frequency of 360 cycles per hour define the fastest cycle rate — useful when the relay follows a high-speed sensor or light curtain in a pick-and-place cell. ## Where this class of safety relay is used The 3SK1121-1CB44 includes a start input, feedback input, and cascading capability — so it can be wired into a multi-zone safety system where several relays monitor different hazard points and share a common start/reset circuit. Its EMC emission meets IEC 60947-5-1 Class A, meaning it is suitable for industrial environments without additional filtering in most panels — though verify if your installation has sensitive electronics nearby that require Class B. ## Panel integration — DIN rail fit and wiring At 22.5 mm wide, 100 mm high, and 121.6 mm deep, it occupies a single DIN-rail module — standard for compact control panels where space is tight. Screw and snap-on mounting lets you clip it onto the rail or bolt it to a backplate; the mounting position is unrestricted. Wire sizes accepted: solid 1x (20–14 AWG) or 2x (18–16 AWG), stranded 1x (20–16 AWG) or 2x (20–16 AWG), and with ferrule 1x (0.5–2.5 mm²) or 2x (0.5–1.0 mm²) — covers most panel wiring from 14 AWG motor leads down to 20 AWG sensor cables.","metaTitle":"Siemens SIRIUS 3SK1121-1CB44 Safety Relay, SIL 3/PL e, 22.5","metaDescription":"Siemens SIRIUS 3SK1121-1CB44 safety relay, SIL 3 / PL e, 24 V DC, 3 A contacts, 22.5 mm wide. Current lifecycle stage. Sourced to order. Request a quote.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","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","Product Category":"Safety relays","Shock Resistance":"10g / 11 ms","Mounting Position":"any","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"safety relays","Overvoltage Category":"3","Design Of The Product":"Relay enabling circuits","Total Current Maximum":"12 A","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","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","Thermal Current Of The Switching Element With Contacts Maximum":"5 A","adjustable OFF-delay time after opening of the safety circuits":"5 ... 300","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms","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/3SK1121-1CB44/alternatives.json"},"ai":{"faq":[{"question":"What is the width and mounting of this safety relay?","answer":"It is 22.5 mm wide and mounts via screw or snap-on onto a DIN rail, in any position."},{"question":"What wire sizes does the 3SK1121-1CB44 accept?","answer":"It accepts solid 1x (20–14 AWG) or 2x (18–16 AWG), stranded 1x (20–16 AWG) or 2x (20–16 AWG), and ferruled 1x (0.5–2.5 mm²) or 2x (0.5–1.0 mm²)."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-1CB44","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/3SK1121-1CB44 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}}