Sick RLY3-EMSS100 Safety Relay

The Sick RLY3-EMSS100 is a compact safety relay designed for monitoring emergency stop circuits, safety gates, and two-hand controls in industrial machinery. Part of Sick’s RLY3 series, this module provides forced-guided relay outputs and meets the requirements of EN ISO 13849 up to Performance Level e and IEC 61508 up to SIL3. It is suitable for applications requiring reliable shutdown of hazardous movements.

Technical Specifications

The RLY3-EMSS100 operates with a supply voltage of 24 V DC (19.2 – 28.8 V). It features two normally open (NO) safety outputs (each rated 6 A at 230 V AC / 24 V DC) and one auxiliary normally closed (NC) output. The safety outputs are forced-guided relays (EN 50205) with a mechanical lifetime of 10 million cycles. Input circuits can be configured for single-channel, dual-channel with or without cross-circuit detection, or automatic/manual reset. Response time is ≤ 30 ms. The housing width is 22.5 mm, suitable for DIN rail mounting (EN 60715). Terminal type: screw-type, removable. Operating temperature range: -25°C to +55°C. Protection rating IP20.

Key Features

• 2 safety outputs (NO) and 1 auxiliary contact (NC)

• Performance Level e (EN ISO 13849) and SIL3 (IEC 61508)

• Single or dual-channel input configuration

• Cross-circuit detection for dual-channel wiring

• Manual or automatic reset selectable

• LED indicators for supply, input status, and output energised

• Compact 22.5 mm housing for space-saving installation

• Forced-guided relay contacts (EN 50205)

• Wide ambient temperature range

Configuration and Wiring

The RLY3-EMSS100 is configured via DIP switches on the front panel. Switch settings determine the operating mode: single-channel without cross-circuit detection (for simple emergency stop buttons), dual-channel with cross-circuit detection (for safety switches with redundant contacts), and reset type (manual or automatic). The device supports monitored manual reset (feedback loop) to ensure that the reset button is released before the relay re-engages. Wiring diagrams are printed on the side of the module. For dual-channel operation with cross-circuit detection, the two input channels must be wired using separate cable cores; a short between them will cause the relay to remain de-energized.

Safety Integrity

The RLY3-EMSS100 is certified by TÜV for use in safety-related applications up to Category 4, PL e according to EN ISO 13849-1, and SIL3 according to IEC 61508. The mean time to dangerous failure (MTTFd) is > 100 years, and the diagnostic coverage (DC) is high. The forced-guided contact construction ensures that any welded contact is detected and prevents the relay from starting the next cycle.

Applications

Typical applications include emergency stop monitoring on machine tools, safety gate interlocking on automated assembly lines, two-hand control systems on presses, and safety mat evaluation. The relay can also be used in light curtain interfaces (with OSSD output evaluation) when combined with appropriate input devices.

Installation and Maintenance

Mount the relay on a 35 mm DIN rail. Ensure proper clearance for heat dissipation. Connect the power supply (A1/A2) to 24 V DC. Connect the emergency stop button (or safety switch) between terminals S11/S12 and S21/S22. The safety outputs (13/14, 23/24) are wired in series with the contactor coils. The auxiliary NC output (31/32) can be used for PLC monitoring. For manual reset, connect a normally open button between S33 and S34. The reset LED flashes until the reset is performed. No periodic proof test is required due to the high diagnostic coverage, but functional testing of the entire safety circuit is recommended annually.

Environmental and Compliance

The RLY3-EMSS100 complies with CE, UL 508 (industrial control equipment), and RoHS. It is designed for pollution degree 2 environments. Operating altitude up to 2000 m. Vibration resistance 2g (10-55 Hz). The module is not suitable for direct switching of inductive loads without snubber circuits; an external contactor should be used for motor loads.

Conclusion

The Sick RLY3-EMSS100 offers a compact, high-performance safety relay for emergency stop and gate monitoring applications. Its flexible configuration, high safety integrity, and ease of wiring make it a reliable choice for machine builders and system integrators.