Pilz PNOZ s4 Safety Relay with 3 Safety Contacts and 1 Auxiliary Contact

Overview

The Pilz PNOZ s4 is a PNOZsigma relay that combines three instantaneous safety contacts with one auxiliary contact in a 22.5 mm housing. A machine builder who has outgrown a two-contact relay can use the Pilz PNOZ s4 to drop a main contactor, a valve supply and a drive enable from the same E-STOP circuit, while the auxiliary N/C contact reports the relay state to a plant controller. The relay evaluates E-STOP pushbuttons, safety gates and light grids or safety switches with detection of shorts across contacts.

Panel builders and plant owners in the Sultanate of Oman and the wider GCC can obtain the Pilz PNOZ s4 from Seven Star LLC, which provides engineering support in Muscat. The Pilz PNOZ s4 datasheet values are printed in the technical details chapter of the operating manual attached to this page. That manual spans several product IDs, among them 24 V DC types with screw or spring terminals and a wide-range 48 to 240 V AC/DC type, so we confirm the exact variant against your control voltage before an order is placed.

Operating Principle

Inside the Pilz PNOZ s4 two independent relay channels are cross-checked by self-monitoring electronics, and a single component failure does not defeat the safety function. Each on-off cycle includes an automatic test of whether the relays have opened and closed correctly. When a connected E-STOP or guard switch opens the input circuit, the three safety contacts release after a typical 10 ms (20 ms at most), and the auxiliary N/C contact closes to indicate the safe state.

Wiring and start behaviour are chosen with a rotary switch behind the front cover. The Pilz PNOZ s4 can run with a single-channel input or with two channels, optionally detecting shorts across contacts, and it can start automatically, on a manual start button, on the rising or falling edge of a monitored start, or after a start-up test of the gate. A monitored start imposes a waiting period of 120 ms on the rising edge or 250 ms on the falling edge, which prevents a stuck start button from re-enabling the machine. One relay type can therefore serve very different safety devices and wiring philosophies.

Engineering Design of the Pilz PNOZ s4

The Pilz PNOZ s4 measures 22.5 mm wide and 120 mm deep, and its height is 98 mm with screw terminals or 100 mm with spring-loaded terminals. The 24 V DC types weigh 185 g and the AC/DC type 210 g. Terminal blocks plug in, so a defective relay can be swapped without touching the field wiring, and the polycarbonate housing mounts in any orientation. The mechanical life of the relay outputs is stated as 10,000,000 cycles, and the contacts use an AgCuNi alloy with a thin gold layer that also switches signal currents as low as 3 mA.

Six LEDs show the supply, the state of both input channels, the switch state of the safety contacts, the start circuit and errors. The manual lists contact ratings for AC1, DC1, AC15 and DC13 duty and the permitted back-up fuses, and a side connector accepts one PNOZsigma contact expansion module whenever more than three safety contacts are needed. For the Pilz PNOZ s4 the maximum line resistance is 30 Ω for single-channel use, which should be checked against long cable runs in large plants.

Key Features

The Pilz PNOZ s4 extends the PNOZsigma concept with an additional safety contact and an auxiliary contact. Main characteristics:

• Three instantaneous safety N/O contacts plus one auxiliary N/C contact, all in a housing only 22.5 mm wide.
• Semiconductor output (24 V, 20 mA) for status signals to a PLC or indicator.
• Rated up to PL e (Category 4) and SIL 3 / SIL CL 3 with a mission time of 20 years.
• Choose single-channel, dual-channel or dual-channel with short detection using one rotary switch.
• Start options cover automatic, manual, monitored (rising or falling edge) and start-up test.
• Supply variants for 24 V DC with screw or spring terminals and for 48 to 240 V AC/DC.
• Plug-in terminal blocks and a side connector for one PNOZsigma contact expansion module.
• Fast release: E-STOP delay of 10 ms typical and 20 ms maximum.

Industrial Applications

Typical uses for the Pilz PNOZ s4 are pump skids, compressor packages, crane and hoist controls, conveyor networks and fabrication machinery where one safety function has to isolate several energy sources. Across Oman and the GCC that means workshops in Sohar and Duqm, utility plants in Salalah and oil and gas support yards, all of which run guards, E-STOP loops and light grids that must be wired in a clean, auditable way. The auxiliary contact allows the Pilz PNOZ s4 to feed a status signal back to the process controller without using a safety output.

Teams that plan bigger safety systems can compare the Phoenix Contact PSR-SCP safety relay, the Yokogawa ProSafe-RS safety instrumented system and the HIMA HIQuad X safety PLC system in our catalog, which cover configurable and programmable safety logic. Pilz reminds users that the PL and SIL values of a single product do not equal those of the complete safety function and that a risk assessment under the machinery rules is required. Seven Star LLC can help choose the voltage type, terminal type and expansion modules that fit the Pilz PNOZ s4 to your cabinet.

Technical Specifications

Key parameters of the Pilz PNOZ s4 taken from the manufacturer operating manual (21396-EN-23):

Request a Quote for Pilz PNOZ s4

For a price and lead time on the Pilz PNOZ s4, send the product ID, control voltage and preferred terminal type to our instrumentation team in Muscat, who will also confirm stock and supply the operating manual on request. Seven Star LLC delivers the Pilz PNOZ s4 across Oman and the GCC and can include contact expansion modules in the same quotation.

Other Pilz models from Seven Star LLC: Pilz PNOZ s3 safety relay, Pilz PNOZ s5 time-delay safety relay and Pilz PNOZ m B0 base unit.