Pilz 240340 PNOZ X4.1P 24VDC Safety Relay

The Pilz 240340, also known as the PNOZ X4.1P 24VDC, is a compact safety relay designed for industrial machine safety applications. It is used to monitor emergency stop circuits, safety gates, light curtains, and two-hand control devices. The device provides two forced-guided safety contacts (N/O) and one auxiliary contact (N/C), enabling integration into safety circuits up to Category 4 (EN ISO 13849‑1) and SIL 3 (IEC 61508). The Pilz 240340 operates on a 24V DC supply and features a manual or automatic reset configuration via a front‑panel selector switch.

Functional Description

The Pilz 240340 safety relay monitors two input channels (S11/S12 and S21/S22) for shorts, cross circuits, and static levels. When both channels are closed simultaneously (e.g., emergency stop pushbutton not pressed), the internal coil energizes, closing the two NO safety contacts. If one channel opens, the relay de‑energizes within the specified response time, opening the safety contacts and stopping the machine. The forced‑guided contact mechanism ensures that any welded contact is detected, preventing the opposite contact from closing. The auxiliary NC contact can be used to signal the status to a PLC or indicator lamp.

Reset Configuration

The reset behavior is configured via a jumper between terminals Y1 and Y2. When the jumper is open, manual reset is selected; a reset button must be pressed after the input channels close to re‑energize the safety outputs. When the jumper is closed, automatic reset is active: the safety outputs close as soon as the input channels are closed. The manual reset input is monitored for short circuits, ensuring a safe restart.

Diagnostic Indicators

The front panel provides three LED indicators: green (PWR) for supply voltage present, green (CH1) for input channel 1 status, green (CH2) for input channel 2 status, and yellow (OUT) for safety output status. A red FAULT LED flashes to indicate cross‑circuit, channel imbalance, or reset circuit errors.

Applications

The Pilz 240340 is used in emergency stop circuits, safety gate monitoring (with interlock switches), light curtain control, two‑hand control systems (type III A/C), and press safety circuits. It is commonly installed in packaging machinery, robotics, conveyor systems, and printing presses.

Installation Guidelines

Mount the relay on a 35 mm DIN rail inside a control cabinet. Connect external emergency stop buttons (positive‑opening contacts) to terminals S11‑S12 (channel 1) and S21‑S22 (channel 2). Use separate, shielded cables for each channel to maintain cross‑circuit detection. Wire the safety outputs (13‑14, 23‑24) in series with the contactor coils. The auxiliary output (41‑42) can be connected to a PLC input for status monitoring. The relay does not require an external fuse, but the input supply should be protected by a 6 A circuit breaker.

Conclusion

The Pilz 240340 PNOZ X4.1P offers a compact, cost‑effective safety relay with forced‑guided contacts, dual‑channel monitoring, and flexible reset options, suitable for safety applications up to PL e / SIL 3.