PILZ 774400 PNOZ 24VDC 2NO 2NC Safety Relay

The PILZ 774400, part of the PNOZ classic series, is a compact safety relay operating at 24 VDC. It features two normally open (NO) safety outputs and two normally closed (NC) auxiliary outputs. This relay is engineered to monitor emergency stop devices, safety gate switches, light curtains, and two-hand controls up to Safety Category 4/PL e (EN ISO 13849-1).

Key Specifications

• Supply voltage: 24 VDC (nominal range 19.2–28.8 V).

• Safety contacts: 2 NO (forcing guided per IEC 60947-5-1).

• Auxiliary contacts: 2 NC (mirror contact).

• Contact rating: 6 A / 240 VAC (resistive), 3 A / 24 VDC.

• Response time: ≤ 20 ms (from input to output).

• Recovery time: ≤ 30 ms after power removal.

Input Circuits

The 774400 provides two dual-channel input circuits (S11-S12 and S21-S22) with cross-circuit detection. It supports automatic or monitored start via configuration of terminals Y1-Y2. Inputs accept dry contacts (emergency stops, limit switches) or OSSD outputs from light curtains. Automatic start is configured by connecting a jumper between Y1 and Y2; monitored start requires an external reset button.

Functional Safety Parameters

According to EN ISO 13849-1, the relay achieves PL e with Category 4 when properly wired for dual-channel redundancy. For IEC 61508, the SIL CL capability is SIL 3. MTTFd (mean time to dangerous failure) exceeds 100 years for standard applications. Diagnostic coverage (DC) is 99% due to cross-circuit and short-circuit detection.

Applications

Common uses include: emergency stop monitoring on industrial machinery, interlocking guard doors on presses or robotic workcells, light curtain interface for perimeter guarding, and two-hand control modules for hydraulic presses. The 2NO safety contacts are typically wired to contactors that cut power to moving parts. The 2NC auxiliary contacts provide status feedback to a PLC or indicator lamp.

Installation Guidelines

Mount on 35 mm DIN rail. Wire terminals according to the diagram on the device label. Use separate power supply for the input circuit to avoid interference. Ensure the external reset button is placed in a safe location (e.g., outside the guarded area). After installation, perform a commissioning test by triggering the emergency stop and verifying the relay de-energizes properly.

Environmental and Mechanical Data

Operating temperature: -10°C to +55°C. Storage temperature: -40°C to +85°C. Relative humidity: 95% non-condensing. Dimensions: 100 mm x 22.5 mm x 120 mm (height x width x depth). Enclosure rating IP40 (device) / IP20 (terminals). Mechanical endurance: 10 million cycles. Electrical endurance: 100,000 cycles at rated load.

Certifications

CE marked, UKCA, cULus Listed (Class I, Div 2), TÜV Nord functional safety certificate, CCC (China). Complies with RoHS and REACH. Replacement part numbers: 774400 replaces older PNOZ 2.0 24VDC models.