{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1220-1AB40","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1220-1AB40","canonicalUrl":"https://aoctrl.com/siemens/3SK1220-1AB40","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1220-1AB40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS safety relay, 3SK1220-1AB40, 24 VDC, screw-type terminals, 17.5 mm width, configurable sensor extension for floating and non-floating sensors.","salesMarkdown":"## What this SIRIUS safety relay does The Siemens 3SK1220-1AB40 is a SIRIUS safety relay configured as a sensor extension module. It sits between your safety sensors (light curtains, interlock switches, e-stops) and the safety controller, handling the wiring and logic for up to two channels. It monitors floating or non-floating sensors, detects cross-circuits, and supports antivalent sensors and two-hand switch inputs — all configurable without software, just by setting the onboard parameters. Runs on 24 VDC nominal, with a tolerance band of 0.8 to 1.2 times the rated value — so it stays happy between about 19.2 V and 28.8 V. The supply is monitored internally; if it dips below dropout, the relay drops its outputs and the machine stops safely. Width is 17.5 mm — one standard DIN-rail module. Depth is 121.6 mm, height 100 mm. Mounts in any position via screw and snap-on mounting. That 17.5 mm width matters when you're packing multiple safety functions into a crowded panel; you can fit a two-channel sensor interface in the same footprint as a single miniature circuit breaker. Screw-type terminals accept solid conductors: 1x (20…14 AWG) or 2x (18…16 AWG). With ferruled stranded wire, it takes 1x (0.5…2.5 mm²) or 2x (0.5…1.0 mm²). Strip length is standard for the terminal block family — the spring pressure is consistent across the SIRIUS range, so a wireman who's landed a 3SK1 before will feel at home here. ## Configurable safety logic — no software needed The 3SK1220-1AB40 is parameterizable for: sensor floating or non-floating, monitored start-up or automatic start, 1-channel or 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, and two-hand switches. That's a lot of flexibility from a module with no programming port — you set it via the input wiring and the start input design. The monitoring of floating sensors and non-floating sensors means it works with mechanical contacts, solid-state outputs, and proximity switches alike. Response time is fixed: the sensor input minimum is 60 ms, and the ON pushbutton input minimum is 0.15 s. No delayed switching on the safety path — it's instantaneous (0 ms delayed). That keeps the safety reaction predictable for risk assessment. Humidity tolerance 10 to 95% RH during operation. Shock resistance 10g / 11 ms. Degree of pollution 3, overvoltage category 3 — that's the industrial environment rating, meaning it's designed for conductive pollution and transient overvoltages common in control panels. UL approved. EMC emissions per IEC 60947-5-1, Class A — suitable for industrial environments, not residential. Power loss max 1.2 W, so no derating concerns in a dense panel.","metaTitle":"Siemens 3SK1220-1AB40 SIRIUS Safety Relay, 24 VDC, 17.5 mm","metaDescription":"Siemens 3SK1220-1AB40 SIRIUS safety relay, 24 VDC, 17.5 mm wide, screw terminals. Configurable sensor extension for floating/non-floating sensors. UL approved. Sourced 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":"17.5 mm","at DC":"0.8 ... 1.2","Height":"100 mm","Maximum":"60 ms","Typical":"60 ms","Rated Value":"24 V","UL approval":"Yes","Safety Switch":"Yes","at DC maximum":"60 ms","During Storage":"-40 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting","Product Category":"Safety relays","Shock Resistance":"10g / 11 ms","Delayed Switching":"0","Mounting Position":"any","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"Sensor extension","Overvoltage Category":"3","power loss [W] maximum":"1.2 W","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)","Design Of Input Start Input":"Yes","Of The Sensor Input Minimum":"60 ms","Type Of Electrical Connection":"screw-type terminals","Insulation Voltage Rated Value":"50 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","Safety-Related Delayed Switching":"0","Monitoring Of Non-Floating Sensors":"Yes","Relative Humidity During Operation":"10 ... 95 %","air pressure according to SN 31205":"900 ... 1 060 hPa","of the ON pushbutton input minimum":"0.15 s","Product Feature Cross-Circuit-Proof":"Yes","Safety-Related Instantaneous Contact":"0","Surge Voltage Resistance Rated Value":"800 V","category according to EN ISO 13849-1":"4","protection class IP of the enclosure":"IP20","stop category according to EN 60204-1":"0","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.","reference code according to EN 61346-2":"F","Magnetically Operated Switch Monitoring":"Yes","reference code according to IEC 81346-2":"F","For Signaling Function Delayed Switching":"0","Suitability For Interaction Press Control":"No","Touch Protection Against Electrical Shock":"finger-safe","safety device type according to IEC 61508-2":"Type B","For Signaling Function Instantaneous Contact":"0","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","performance level (PL) according to ISO 13849-1":"e","vibration resistance according to IEC 60068-2-6":"5 ... 500 Hz: 0.75 mm","PFHD with high demand rate according to EN 62061":"1E-9 1/h","suitability for operation device connector 3ZY12":"Yes","PFDavg with low demand rate according to IEC 61508":"7E-6","Installation Altitude At Height Above Sea Level Maximum":"4 000 m; Derating, see Product Notification 109792701","Required Spacing With Side-By-Side Mounting At The Side":"0 mm","Recovery Time After Opening Of The Safety Circuits Typical":"30 ms","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3SK1220-1AB40/alternatives.json"},"ai":{"faq":[{"question":"What is the depth of the 3SK1220-1AB40?","answer":"The depth is 121.6 mm. That's the dimension from the DIN-rail mounting surface to the front of the housing. Height is 100 mm, width is 17.5 mm."},{"question":"What wire sizes does the 3SK1220-1AB40 accept?","answer":"Solid wire: 1x (20…14 AWG) or 2x (18…16 AWG). Stranded with ferrule: 1x (0.5…2.5 mm²) or 2x (0.5…1.0 mm²). The terminals are screw-type."},{"question":"What compliance documentation does Siemens provide for 3SK1220-1AB40?","answer":"The module carries UL approval and is EMC tested to IEC 60947-5-1, Class A. Typical Siemens documentation includes a declaration of conformity (CE), UL file listing, and environmental compliance data (RoHS/REACH) available through the support portal."},{"question":"Where can I buy the 3SK1220-1AB40 and get current pricing?","answer":"This safety relay is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time — submit an RFQ for a firm price and lead time."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1220-1AB40","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/3SK1220-1AB40 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}}