Siemens 3sk1111-2ab30

By Abdullah Zahid
13 min read
Siemens 3SK1111-2AB30 SIRIUS safety relay with 3 NO contacts on DIN rail in industrial control panel

Siemens 3SK1111-2AB30 SIRIUS Safety Relay — Specifications, Pricing, and Selection Guide

If you are a controls engineer or procurement specialist evaluating the Siemens 3SK1111-2AB30 for a machinery safety circuit, the core decision usually comes down to three things: does the SIL 3 / PLe certification satisfy your risk assessment obligation, does the 24V AC/DC supply match your cabinet infrastructure, and do the three NO plus one NC contacts cover your load and signaling requirements? This is a SIRIUS family safety relay rated to Performance Level e per ISO 13849-1 and SIL 3 per IEC 62061, with a 10-million-cycle mechanical service life and spring-loaded terminals designed to reduce commissioning time. If those parameters align with your application, this page will give you everything needed to confirm the selection and order with confidence.

If you have already confirmed this is the right part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the 3SK1111-2AB30 — and Who Shouldn't

The Siemens 3SK1111-2AB30 is the right choice for engineers who need a certified, compact safety relay with multiple independent load outputs at 24V. Buy this model if all of the following apply:

  • Your control cabinet uses a 24V AC or 24V DC supply rail within the 20.4V to 28.8V operating window
  • Your application requires three independent safety-critical NO contacts plus one NC signaling contact
  • Your machinery risk assessment mandates SIL 3 (IEC 62061) or Performance Level e / Category 4 (ISO 13849-1)
  • Monitored start and closed-loop feedback input verification are required by your safety architecture
  • Each load circuit draws no more than 5A, with total output current not exceeding 12A across all three NO contacts
  • DIN rail mounting in a panel with ambient operating temperature between -25°C and +60°C

If you need only one NO contact output, the 3SK1111-1AB30 is the appropriate lower-cost alternative. If your cabinet runs at 110–240V AC/DC and you cannot dedicate a 24V supply rail, the 3SK1111-2AW20 is the correct variant. If you require four or more outputs, consider the 3SK1111-3AE30.

On this page:

What the 3SK1111-2AB30 Actually Does in a Safety System

The Siemens 3SK1111-2AB30 is a SIRIUS basic-unit safety relay — its formal descriptor is: safety relay, basic unit, standard series, relay enabling circuits 3 NO contacts plus relay signaling circuit 1 NC contact. In practical terms, it acts as the certified switching interface between a safety controller or PLC output and the field equipment that creates hazardous motion. The relay reads start signals and feedback confirmation from the safety architecture, processes them through internally monitored logic, and either enables or interrupts the three independent NO contact circuits controlling loads such as motor contactors, solenoids, or pneumatic valves. The single NC contact provides a parallel signaling path for alarm indicators, horn relays, or status chains.

What distinguishes this model from a standard relay is the cross-circuit-proof design that prevents any single fault from bridging the safety circuit and the load circuit — a mandatory requirement for Category 4 / PLe installations. The integrated feedback monitoring input eliminates the need for external signal validation hardware in most standard single-axis safety loops, keeping BOM count low. The spring-loaded terminal design accepts 20–16 AWG stranded wire in single or double configurations, removing the risk of screw-terminal loosening under vibration. Mechanical service life is rated at 10,000,000 operating cycles, which translates to approximately 5 to 10 years of continuous operation in typical industrial duty cycles before a scheduled replacement is warranted.

Typical System Architecture for the 3SK1111-2AB30

The 3SK1111-2AB30 sits between the safety controller output stage and the load-side field equipment, acting as the final switching element in a monitored enable chain. Below is the typical component sequence in a standard safety relay application:

  • Safety PLC or safety controller sends a validated start output signal to the IN1 terminal of the 3SK1111-2AB30
  • Safety input devices (E-stop buttons, gate switches, safety mats) feed their status into the safety controller, which evaluates logic before driving IN1
  • Feedback from the load-side contactors or downstream safety devices connects back to IN2 for closed-loop verification inside the relay
  • The relay's three NO contacts (T1, T2, T3) energize the motor contactors, solenoids, or valve coils that control hazardous motion
  • The NC contact (T4) feeds the alarm chain — horn relay, beacon, or supervisory PLC status input — confirming safe-state condition

Typical Applications: Where Engineers Deploy This Relay

Emergency stop circuits are the most common deployment. Dual-channel safety stop buttons wire to the safety controller inputs, the controller evaluates the stop condition, and its output drives IN1 of the 3SK1111-2AB30. When the E-stop is activated, the NO contacts de-energize main motor contactors within the relay's specified recovery time of 10 ms, while the NC contact simultaneously drives an alarm beacon or horn.

Machinery guard interlock systems — particularly on injection molding machines, metal stamping presses, and packaging equipment — use the 3SK1111-2AB30 to gate hazardous motion until all access door safety switches confirm closed. The feedback input monitors the door switch circuit, and motion is enabled only when all conditions pass simultaneously, preventing inadvertent bypass.

Pump and compressor startup sequencing applications use the relay to coordinate a run-permission chain: a pressure sensor or flow switch output feeds back to IN2, the start authorization signal arrives at IN1, and the NO contacts energize the pump motor contactor only when both conditions are satisfied. This pattern is common in food and beverage processing and chemical batch systems.

Work-cell motion authorization in automotive assembly and robotic work cells uses the relay as the final gate before robot arm or conveyor motion is permitted. Presence-detection safety mats or area scanners feed into the safety controller, which clears IN1 only after confirming the cell is clear, with the 3SK1111-2AB30 providing the certified output switching action at Category 4 integrity.

Application Typical Deployment
Emergency stop circuit Safety controller output to IN1; NO contacts de-energize motor contactor; NC contact drives alarm
Guard door interlock Safety switches on access doors; feedback to IN2; NO contacts gate hazardous motion enable
Pump / compressor sequencing Start signal from PLC to IN1; pressure sensor feedback to IN2; NO contacts enable motor
Robotic work cell authorization Safety mat / area scanner logic cleared in controller; IN1 enables robot motion via NO contacts
Turntable / rotary actuator protection Personnel-clear verification from safety switches; relay gates rotation enable signal
Automatic light tower control Hazardous motion status signal drives IN1; NC contact energizes warning beacon / horn circuit

Key Electrical and Safety Specifications

Parameter Value
Supply voltage 24V AC / 24V DC (range: 20.4V to 28.8V)
Output contacts 3 NO (safety-related, instantaneous) + 1 NC (signaling)
Max switching current per NO contact 5A at 24V DC
Max total output current 12A across all three NO contacts
Minimum switching current 5 mA at 17V
Safety Integrity Level SIL 3 (IEC 62061, IEC 61508)
Performance Level PLe / Category 4 (ISO 13849-1)
PFHD (high demand) 1.7E-9 per hour
Mechanical service life 10,000,000 cycles
Operating temperature range -25°C to +60°C

Full technical specifications are available on the product page at LeadTime.ca.

3SK1111-2AB30 vs. Other SIRIUS Variants: Which One Do You Need?

Model Supply Voltage NO Contacts NC Contact SIL Rating Best Use Case
3SK1111-1AB30 24V AC/DC 1 1 SIL 3 Single output, basic signaling applications
3SK1111-2AB30 24V AC/DC 3 1 SIL 3 Multi-output standard applications — this model
3SK1111-3AE30 24V AC/DC 4 1 SIL 3 Expanded outputs, more complex safety logic
3SK1111-1AW20 110–240V AC/DC 1 1 SIL 3 Higher voltage cabinet, single output
3SK1111-2AW20 110–240V AC/DC 3 1 SIL 3 Higher voltage cabinet, multi-output

If your control cabinet runs a dedicated 24V rail and your application requires three independent safety-critical load outputs with SIL 3 certification, the 3SK1111-2AB30 is the correct selection — check current availability and pricing at LeadTime.ca.

Expert Verdict: Honest Assessment for Procurement Decision

The Siemens 3SK1111-2AB30 earns its place in standard machinery safety panel design because it delivers a genuinely useful combination: three independently switched NO contacts at SIL 3 / PLe certification, a PFHD of 1.7E-9 per hour, a proof test interval of 20 years per IEC 61508, and spring-loaded terminals that genuinely reduce commissioning time compared to screw-terminal alternatives. The 10-million-cycle mechanical service life is verified by Siemens and is consistent with field performance across the installed SIRIUS base in packaging, stamping, and food processing sectors. The integrated feedback monitoring input means that, in many single-axis applications, you do not need additional external signal validation hardware — a real BOM simplification at the panel design stage.

The honest limitations are worth stating. This relay does not include integrated short-circuit protection — you must install an external 6A gL/gG fuse, a 3A Type A circuit breaker, or equivalent on the 24V supply side before commissioning. The 5A per contact / 12A total switching rating means this relay controls pilot devices, solenoids, and motor contactors — it is not a direct motor switching device. If your load analysis shows direct motor currents exceeding 5A per circuit, you need a correctly sized motor contactor downstream of these contacts. And if your cabinet does not accommodate a dedicated 24V supply rail, the 3SK1111-2AW20 at 110–240V is a cleaner fit than adding a 24V converter solely for this relay.

From a procurement standpoint, the 3SK1111-2AB30 sits in the category of parts that are generally available but subject to lead time variability — typical lead time from major distributors runs 2 to 4 weeks, with direct Siemens factory orders extending to 6 to 8 weeks during constrained periods. For projects with hard commissioning dates, confirming stock before design freeze is a practical risk-reduction step. LeadTime.ca maintains inventory and sourcing access for the SIRIUS family and can advise on volume pricing at 10+ units. If this matches your system requirements, view current stock and pricing at LeadTime.ca.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

Wiring and Installation Overview

The following points cover the key requirements for installing the 3SK1111-2AB30. For complete wiring diagrams and step-by-step procedures, refer to the official Siemens product datasheet and manual.

  • Mount the relay on a standard 35 mm DIN rail; verify ambient operating temperature at the installation point is within -25°C to +60°C and that installation altitude does not exceed 2,000 m without derating
  • Connect 24V supply to A1+ and the return to A2-; install a 6A gL/gG fuse or appropriately rated circuit breaker (Type A 3A, Type B 2A, or Type C 1A) on the 24V supply line before the relay — this is mandatory, as no internal short-circuit protection is included
  • Route safety controller start output to IN1, feedback signal from load-side contactors or downstream safety devices to IN2; use 20–16 AWG stranded wire in the spring-loaded terminals; maximum sensor circuit cable length is 2,000 m total with 1.5 mm copper conductor
  • Connect NO contact terminals T1, T2, T3 to the load equipment (motor contactors, solenoid coils, valve actuators); connect T4 (NC) to the alarm or signaling chain
  • After wiring, apply 24V power and conduct a functional proof test: confirm NO contact pickup on IN1 activation within the specified make time, confirm 10 ms recovery on dropout, and verify feedback loop response before releasing for production — document the proof test date for compliance records

Compatible Modules and System Expansion

The 3SK1111-2AB30 operates as a standalone basic unit within the SIRIUS safety relay family. When your application requires additional outputs or expanded diagnostics beyond what this single unit provides, the following SIRIUS variants integrate directly within the same architecture:

  • 3SK1111-1AB30 — Single NO contact variant at 24V AC/DC, SIL 3 certified; use when only one safety-critical output is required, reducing panel space and cost
  • 3SK1111-3AE30 — Four NO contacts at 24V AC/DC, SIL 3 certified; use when three outputs are insufficient for a complex multi-actuator interlock
  • 3SK1111-4EP30 — Expanded SIRIUS module with internal diagnostics and pilot indicators; suitable when onboard status visibility is required without adding external indication hardware
  • 3SK1111-2AW20 — Same 3 NO + 1 NC contact configuration as the 2AB30 but rated for 110–240V AC/DC supply; use in cabinets without a dedicated 24V rail

Wrong-Part Prevention Checklist Before You Order

Before placing an order for the Siemens 3SK1111-2AB30, run through each of the following checks against your application requirements. These are the most common sources of wrong-part orders for this model:

  1. Verify supply voltage is 24V AC or 24V DC, not 110V or 230V
  2. Confirm three NO contacts and one NC contact match your load and signaling requirements
  3. Check that safety certification (SIL 3, PLe) meets your machinery directive obligation
  4. Validate input configuration supports monitored start and feedback sensing (this model does)
  5. Confirm switching current rating (5A max per contact, 12A total) exceeds load demands
  6. Verify terminal type is spring-loaded, not plug-in socket (this model uses spring terminals)
  7. Check installation altitude does not exceed 2,000 m or 4,000 m depending on derating tables
  8. Ensure ambient temperature during operation stays within -25 to +60°C range

If any of these checks identifies a mismatch, contact the LeadTime.ca team to confirm the correct variant before ordering — wrong safety relay selections can cause compliance gaps and commissioning delays that are far more costly than the part itself.

Frequently Asked Questions

Does the 3SK1111-2AB30 require an external fuse or circuit breaker?

Yes — this is a mandatory installation requirement, not optional. The relay module contains no integrated short-circuit protection. You must install a 6A gL/gG fuse, a Type A 3A circuit breaker, a Type B 2A circuit breaker, or a Type C 1A circuit breaker on the 24V supply line feeding the relay. Without this protection, inductive load switching surges can weld relay contacts and disable the entire safety circuit.

What is the difference between the IN2 feedback input and the IN3 cascading input?

IN2 is the feedback input — it monitors the status of the load-side switching elements (typically the auxiliary contacts of the downstream motor contactors) and reports back to the relay for closed-loop verification. IN3 is used for cascading or functional switching, allowing multiple safety relays to be chained in series for more complex safety architectures. Wiring a cascading signal to IN2 or vice versa is one of the most common installation errors with this model and will result in incorrect safety monitoring behavior.

Is the 3SK1111-2AB30 suitable for direct motor switching, or does it require a downstream contactor?

The relay's NO contacts are rated at 5A maximum per contact at 24V DC, with 12A total across all three outputs. This makes the relay suitable for switching pilot loads — motor contactors, solenoid coils, valve actuators, and indicator loads. It is not designed for direct motor switching at higher currents. If your motor load exceeds 5A per circuit, the relay should switch a correctly sized motor contactor downstream.

What is the PFHD value and why does it matter for machinery certification?

PFHD stands for Probability of Dangerous Failure per Hour in high-demand mode. The 3SK1111-2AB30 has a PFHD of 1.7E-9 per hour, which places it comfortably within the SIL 3 and PLe architecture requirements. During a machinery safety assessment under ISO 13849-1 or IEC 62061, the PFHD value of each component in the safety function chain is summed to verify the overall system meets the required integrity level. A PFHD of 1.7E-9 provides significant margin even in systems with multiple safety relay stages in series.

What is the typical lead time for the 3SK1111-2AB30, and how can I get it faster?

Typical lead time from major distributors is 2 to 4 weeks. Direct Siemens factory orders can extend to 6 to 8 weeks during supply-constrained periods. If your project has a hard commissioning date, checking distributor stock before design freeze is strongly recommended. LeadTime.ca maintains sourcing access for the SIRIUS family globally — contact the team directly to confirm current availability and lead time for your quantity.

Can the 3SK1111-2AB30 be used with non-floating sensors and magnetically operated switches?

Yes. The relay's input configuration is compatible with floating and non-floating sensors as well as magnetically operated switches. The minimum monitored start pulse duration is 150 ms, and the input circuit is cross-circuit-proof, preventing bridging faults between the safety input and the load switching circuits.

Why Order the 3SK1111-2AB30 from LeadTime.ca

  • LeadTime.ca ships worldwide — no geographic restriction on sourcing, whether you are building panels in North America, Europe, or Southeast Asia
  • SIRIUS family parts including the 3SK1111-2AB30 are actively stocked and sourced; contact the team for real-time availability before committing to a build schedule
  • Volume pricing is available at 10+ units — useful for OEMs and panel builders with multi-machine projects
  • The team can assist with cross-referencing variant selections and confirming correct part numbers before order placement, reducing wrong-part risk
  • Hard-to-source or back-ordered SIRIUS modules can be tracked and expedited through LeadTime.ca's global distributor network

At-a-Glance Summary

  • Official product: SIRIUS safety relay, basic unit, standard series — 3 NO enabling contacts plus 1 NC signaling contact
  • Supply voltage: 24V AC or 24V DC, operating range 20.4V to 28.8V
  • Safety certification: SIL 3 (IEC 62061 / IEC 61508), PLe / Category 4 (ISO 13849-1)
  • PFHD: 1.7E-9 per hour; proof test interval: 20 years per IEC 61508
  • Safe Failure Fraction: 99%; Hardware Fault Tolerance: 1; Type A device classification
  • Maximum switching current: 5A per NO contact, 12A total across all three NO contacts
  • Mechanical service life: 10,000,000 operating cycles
  • Operating temperature: -25°C to +60°C; IP20 finger-safe enclosure
  • Terminal type: spring-loaded, 20–16 AWG stranded wire, single or double entry
  • Maximum sensor circuit cable length: 2,000 m total with 1.5 mm copper conductor
  • External short-circuit protection required: 6A gL/gG fuse or rated circuit breaker — not integrated
  • Key alternatives: 3SK1111-1AB30 (single NO, 24V), 3SK1111-2AW20 (3 NO, 110–240V), 3SK1111-3AE30 (4 NO, 24V)
  • Typical distributor lead time: 2 to 4 weeks; factory direct: 6 to 8 weeks