{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-1CB42","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-1CB42","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-1CB42","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1CB42","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-1CB42 safety relay, 24 V DC, 3 A switching current, SIL 3 / PL e, 22.5 x 100 x 121.6 mm, screw and snap-on mounting.","salesMarkdown":"## Safety relay for enabling circuits — SIL 3 / PL e at 24 V DC The Siemens 3SK1121-1CB42 is a SIRIUS safety relay designed for relay enabling circuits in safety-related applications, rated SIL 3 per IEC 61508 and IEC 62061, and PL e per ISO 13849-1. It operates on a 24 V DC supply and switches up to 3 A at 24 V, 115 V, or 230 V. SIL 3 and PL e are the highest single-device safety integrity levels for this class — the relay can be used in safety functions up to Category 4 architecture per EN 13849-1, with a safe failure fraction of 99 %. The 3 A switching current at 24–230 V AC/DC covers most pilot-duty loads: contactor coils, solenoid valves, and indicator lamps. The total current through the relay must not exceed 12 A. Response time is 30 ms typical, 40 ms maximum on pickup, and 110 ms maximum on DC dropout — fast enough for emergency-stop chains but not for light-curtain blanking (which needs sub-ms). The sensor input minimum pulse duration is 75 ms, meaning the safety input must see a valid signal for at least that long before the relay responds — this filters contact bounce on E-stop buttons but also means the relay cannot follow a fast-opening guard door switch without a delay. Operating frequency is capped at 360 cycles per hour, or one cycle every 10 seconds, which is fine for machine cycle start/stop but not for high-speed indexing. ## Mounting and wiring in the panel The 22.5 mm width matches the SIRIUS compact footprint — three units fit in a standard 70 mm wide slot. Wire termination accepts solid conductors 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). Strip length 8 mm for spring-cage terminals. Shock resistance 10g / 11 ms. EMC emission meets IEC 60947-5-1 Class A (industrial limits). Power loss is 2.5 W maximum, so no forced cooling needed in a standard cabinet.","metaTitle":"Siemens 3SK1121-1CB42 SIRIUS Safety Relay, SIL 3 / PL e, 24","metaDescription":"Siemens 3SK1121-1CB42 SIRIUS safety relay, 24 V DC, 3 A switching current, SIL 3 / PL e, 22.5 mm wide. Current production. Quoted to order.","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":"0.5 ... 30","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/3SK1121-1CB42/alternatives.json"},"ai":{"faq":[{"question":"How do I get pricing and availability for 3SK1121-1CB42?","answer":"Submit an RFQ through this listing. Availability and current pricing are confirmed at quote time through independent distribution channels."},{"question":"What is the depth of 3SK1121-1CB42?","answer":"The depth is 121.6 mm, which fits standard 200 mm deep enclosures with clearance for wiring."},{"question":"What wire sizes does 3SK1121-1CB42 accept?","answer":"Solid wire: 1x (20–14 AWG) or 2x (18–16 AWG). Stranded: 1x (20–16 AWG) or 2x (20–16 AWG). Ferruled: 1x (0.5–2.5 mm²) or 2x (0.5–1.0 mm²)."},{"question":"What safety integrity levels does 3SK1121-1CB42 meet?","answer":"SIL 3 per IEC 61508 and IEC 62061, PL e per ISO 13849-1, with a safe failure fraction of 99 %."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-1CB42","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/3SK1121-1CB42 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}}