Pilz 751134 PNOZ s4 C Safety Relay
The Pilz 751134 (PNOZ s4 C) is a compact safety relay designed for emergency stop circuits, safety gate monitoring, and light curtain evaluation. It operates on a wide AC supply voltage range of 48–240V AC (50/60 Hz) and provides two positively guided safety outputs (NO) and two auxiliary outputs (NC). The unit is certified for SIL 3 (IEC 61508) and PL e (ISO 13849-1), making it suitable for demanding safety applications.
Input Channels
The relay features two redundant safety input channels (S12 and S22) that can be connected to emergency stop buttons (dual-channel with cross-circuit detection) or to OSSD outputs from light curtains. The inputs accept 24V DC signals (internally derived from the AC supply). For single-channel operation, a jumper is used. Input response time: < 20 ms. The unit also includes a feedback loop (Y1-Y2) for monitoring external contactors.
Output Specifications
2 safety outputs (13-14, 23-24): NO contacts, forced-guided, rated 6A at 250V AC (resistive) / 5A at 24V DC.
2 auxiliary outputs (41-42, 51-52): NC contacts, rated 3A at 250V AC.
Maximum total current per common: 10 A. The safety outputs are redundant: two internal relays with their contacts in series to achieve fail-safety. Output response time: < 25 ms (off-delay).
Power Supply
Supply voltage: 48–240V AC (47–63 Hz) or 48–240V DC (with derating). Tolerance: -15% / +10%. Power consumption: 3 VA (AC) or 2.5 W (DC). The relay is protected against short-term supply interruption (< 20 ms). A green LED indicates power on. The unit has a removable screw-terminal block for easy wiring.
Safety Ratings and Certifications
PFHd: 2.3 × 10⁻⁹ (SIL 3). MTTFd: 150 years. DCavg (diagnostic coverage) > 99%. The relay meets EN 60947-5-1, EN 60204-1, and ISO 13849-1. It is certified by TÜV, UL, and CSA. The device has a mission time of 20 years (per IEC 61508-2).
Environmental and Physical
Dimensions: 22.5 mm width x 98 mm height x 105 mm depth. Weight: 160 g. Mounting: DIN rail (35 mm). Operating temperature: -10°C to +55°C; storage: -40°C to +85°C. Humidity: 10% to 95% non-condensing. Protection class: IP20. Vibration: 1 g (10–55 Hz). The housing is polycarbonate (UL94 V-0).
Start and Reset Behavior
The relay can be configured for automatic start (jumper on S33-S34) or monitored manual reset (using an external pushbutton). In monitored reset mode, the reset button must be pressed after the input circuit is closed, and the button must open again before re‑application – this detects stuck buttons. The unit also supports a start-up test that detects welded contacts on external devices.
Typical Applications
Emergency stop buttons on packaging machines, conveyor systems, printing presses, and robotics. It is also used for guard door monitoring with locking devices. The wide AC supply range allows direct connection to machine control transformers without an auxiliary 24V DC supply.
Diagnostics and LED Indicators
LEDs: PWR (green), CH1 (green, input channel 1), CH2 (green), OUT (green, safety output). A red LED flashes to indicate error code (e.g., cross-circuit, shorted reset button). The relay includes a built-in fault memory that can be reset by power cycling.
Ordering and Documentation
Pilz order number: 751134 (PNOZ s4 C). The relay is supplied with a terminal block and a label sheet. Manual: PNOZ s4 C Operating Manual (1002631-EN-01). RoHS compliant.
