Comprehensive Genuine New Safety Relay PILZ PNOZ 16SP 777077 Precision Performance for Industrial Equipment

The PILZ PNOZ 16SP (Order No. 777077) is a standalone safety relay designed to provide a safety-related interruption of a safety circuit—the kind of dependable, deterministic behavior you want when an emergency stop is pressed or a safety gate is opened. In this 777077 variant, the relay is built around a practical mixed-supply concept: U1 = 240 VAC for the primary supply and U2 = 24 VDC for the secondary supply, making it a strong fit for panels that distribute mains-derived control voltage while still interfacing with modern 24 VDC signaling. 

From the product description, the 777077 is specified with inputs for 1-/2-channel wiring (with or without detection of shorts across contacts), outputs of 2 N/O safety contacts plus 2 semiconductor outputs, and automatic/manual start, all packaged in a 45 mm-wide housing with plug-in screw terminals. It is also listed for common safety tasks including monitoring of E-STOP and safety gates, and it supports a feedback loop for external device monitoring. 

Quick Technical Overview (Order No. 777077)

How the PNOZ 16SP Behaves in Real Operation

A safety relay’s job is simple: it should enable a machine only when the safety loop is healthy, and it should drop out quickly and predictably when the loop is broken.

The operating manual explains the logic clearly: when supply voltage is present, the unit becomes ready for operation only when the feedback loop (Y1–Y2) and the start circuit (S33–S34) are closed. With a healthy input circuit (for example, an E-stop not actuated), the safety contacts 13–14 and 23–24 close; when the input circuit opens (E-stop actuated), those contacts are redundantly opened. It also describes a semiconductor output (Y32) that reflects the switch state, and another (Y35) related to supply/fuse status. 

That combination—redundant safety contacts for power removal and semiconductor outputs for machine status—makes the 777077 easy to integrate into classic contactor-based safety circuits without sacrificing basic diagnostics. The manual also states safety features such as redundancy with built-in self-monitoring and automatic testing of correct relay operation each on-off cycle. 

Input Wiring, Restart Strategy, and Short Detection

The 777077 supports both single-channel and dual-channel wiring. Dual-channel mode can include detection of shorts across contacts, helping catch certain wiring faults that would otherwise “fake” a safe condition. 

You also get two standard restart philosophies:

• Automatic start: the unit becomes active once the input circuit is closed.

• Manual start: the unit becomes active once both the input circuit and the start circuit are closed. 

This matters because restart behavior is where many machines become unintentionally dangerous. The manual explicitly warns that if automatic start is used (or if the start contact is bridged by a fault), the unit may start up automatically when the safeguard is reset (for example, when an E-stop is released), and you should use external circuit measures to prevent unexpected restart. 

One more practical note: the manual points out that the device does not recognize short circuits or shorts across contacts in the start/feedback loop, and it recommends suitable measures such as protected or separate installation (fault exclusion) for that wiring. 

Safety Performance Context (PL/SIL Data and Mission Time)

For safety engineering work, you don’t just buy a relay—you validate a safety function.

The operating manual includes safety characteristic data that depends on operating mode. For example, it lists that a 2-channel sensor operating mode can reach PL e, Category 4 and SIL 3, with a stated mission time TM = 20 years in the table. It also lists a separate line for short circuit-forming safety mats at PL c, Category 1 and SIL 1, also with TM = 20 years. 
The same page emphasizes that a safety function’s SIL/PL values are not identical to the SIL/PL values of individual products and may differ—so you still need to calculate and validate the complete function (device + wiring + contactors + mechanics). 

Lifecycle Note: Discontinued Status and Replacement Planning

According to Pilz’s own product page, Order No. 777077 has been discontinued. Pilz lists the following products as fully compatible in function: 750104, 751104, 750134, 751134, with the important caveat that you should confirm all framework conditions and parameters for your specific application. 

That’s valuable if you are doing maintenance support for installed machines: you can keep your documentation and wiring concept stable, while sourcing an approved successor part—without improvising a different safety architecture mid-service call.

Summary

The PILZ PNOZ 16SP 777077 is a compact, panel-friendly safety relay for classic machine safety circuits—E-stop and safety gate monitoring, 2 N/O positive-guided safety contacts, 2 semiconductor outputs for status, automatic/manual start, and optional short detection depending on wiring. Its 240 VAC / 24 VDC supply arrangement targets mixed-voltage control panels, and its documentation provides clear guidance on operating modes, restart behavior, and safety characteristic data used in PL/SIL assessments.