Allen-Bradley 440R-EM4R2 Guardmaster Safety Relay

The Allen-Bradley 440R-EM4R2 (also known as Guardmaster EM4R2) is a compact safety relay designed for monitoring emergency stop buttons, safety gates, and light curtains. It features 4 safety inputs (dual-channel) and 2 normally open safety outputs, plus one auxiliary normally closed output. Certified to Category 4, Performance Level e (ISO 13849-1) and SIL CL3 (IEC 61508), the 440R-EM4R2 provides reliable safety functionality in a 45 mm wide housing.

Technical Specifications

Supply voltage: 24 V DC (19.2-28.8 V). Power consumption: 2.5 W. Safety inputs: 4 channels, dual-channel capable with cross-circuit detection. Input current: 25 mA per channel. Safety outputs: 2 NO (force-guided relays), rated at 6 A (AC-15, 230 V) or 3 A (DC-13, 24 V). Auxiliary output: 1 NC relay contact, 2 A. Response time: ≤ 30 ms. Reset type: automatic or monitored manual (selectable via DIP switch). Diagnostic LEDs: power, input status (2 LEDs per channel), output status, fault. Dimensions: 45 mm (W) × 100 mm (H) × 115 mm (D). Operating temperature: -10°C to 55°C. Protection rating: IP20. DIN rail mounting (35 mm). Screw terminal blocks included.

Key Features

• 4 safety inputs (single or dual-channel with cross-circuit detection)

• 2 NO safety output relays (6 A)

• 1 NC auxiliary output for PLC monitoring

• Selectable automatic or manual monitored reset

• 4 independent input channels can be grouped for multiple safety zones

• Self-diagnostics and internal redundancy

• LED status for each input, output, and fault

• Removable terminal blocks for easy wiring

Safety Functions

The 440R-EM4R2 can monitor up to 4 independent safety input devices. Each input channel can be configured as single-channel (for simpler devices) or dual-channel with cross-circuit detection. For emergency stop applications, typically two input channels are used per device. The relay also supports feedback monitoring: an external contactor feedback loop can be connected to ensure that contactors have dropped out before resetting. The manual reset can be monitored to prevent short-circuited reset buttons. The auxiliary output (NC) provides status to a PLC for diagnostic purposes.

Configuration

Configuration is performed using DIP switches on the front panel:

• Switch 1: Reset mode (OFF = automatic reset, ON = monitored manual reset)

• Switch 2: Feedback monitoring (OFF = disabled, ON = enabled, requires feedback signal)

• Switches 3-6: Channel configuration for each input pair (single/dual, cross-circuit detection on/off)

The relay is delivered with default settings (all switches OFF). The DIP switch settings are read only when power is applied; changes made during operation require a power cycle.

Applications

Typical applications include:

• Emergency stop monitoring on CNC machines, presses, saws

• Safety gate interlocking on robotic cells and conveyors

• Two-hand control stations for manual feed presses

• Light curtain and safety mat evaluation

• Enabling switch monitoring for teach pendants

Installation and Wiring

Mount the 440R-EM4R2 on a 35 mm DIN rail. Connect 24 V DC power to A1 (+) and A2 (-). Wire safety input devices to terminals S11/S12, S21/S22, S31/S32, and S41/S42. For dual-channel operation, use two adjacent inputs (e.g., S11 and S21). For monitored reset, connect a normally open pushbutton between S33 and S34, and connect the feedback loop from external contactors to S35. Safety outputs are normally open contacts at terminals 13-14 and 23-24; these control the safety contactor coils. Auxiliary NC output is at terminals 41-42. All wiring should comply with local standards and ISO 13849-2. Use appropriate cable sizes (0.5-2.5 mm²).

Diagnostics and LED Indications

The relay includes a green power LED and two yellow LEDs per input channel. Output energization is indicated by green LEDs. A red fault LED flashes to indicate wiring errors (e.g., cross-circuit, shorted reset button). Normal operation: all input LEDs (for closed safety switches) and output LED are on. In a safety demand, output LED turns off and input LEDs may indicate the open contact. For troubleshooting, refer to the fault code table in the user manual (e.g., 1 flash = reset circuit shorted, 2 flashes = cross-circuit input).

Environmental and Compliance

The 440R-EM4R2 is CE, UL, TÜV certified. It meets EN ISO 13849-1 (Cat. 4, PL e), EN 62061 (SIL CL3), and EN 60204-1. It is RoHS compliant. Operating temperature: -10°C to 55°C. Storage: -40°C to 85°C. Humidity: 5-95% non-condensing.

Conclusion

The Allen-Bradley 440R-EM4R2 Guardmaster safety relay provides a compact, flexible solution for safety monitoring in industrial machinery. Its 4 input channels, 2 safety outputs, and selectable reset modes make it suitable for a variety of applications requiring Category 4/PL e safety integrity.