Product Introduction: The SIEMENS 3TH2031-0HY4 is a versatile contactor relay, part of the renowned Sirius 3TH series. It functions as a four-pole auxiliary contactor, energized by a 24V AC or DC coil. Its primary role is to reliably switch control circuits, signals, and small loads in industrial automation panels, machine controls, and building management systems.
The Sirius 3TH series of contactor relays are industry-standard components for control and auxiliary switching tasks. The 3TH2031-0HY4 model is specifically designed to provide reliable, multi-pole switching capability driven by a low-voltage control signal. Unlike power contactors that switch motors, this device is optimized for control circuits—carrying the logic signals, interlocks, and commands that orchestrate the operation of larger machines. It acts as an intermediary, allowing a low-power signal from a programmable logic controller (PLC), timer, or sensor to safely control multiple isolated circuits or to interface with different voltage levels.
The device features four normally open (NO) contacts. This configuration allows it to switch up to four independent control circuits simultaneously with a single coil command. This is invaluable for implementing complex interlocking logic, controlling multiple indicator lamps, or sequencing operations where several actions must be initiated at the same time from one control point.
A significant feature is its coil designed for both 24V AC and 24V DC operation. This universality offers exceptional flexibility in system design, as the same relay can be used in panels powered by standard AC control transformers or modern DC power supplies commonly found in PLC systems. It simplifies inventory and increases application range.
Engineered for high density in control panels, the relay has a compact footprint. It is designed for DIN rail mounting, enabling quick installation and neat cabinet layout. The clear transparency cover allows for easy visual inspection of the contact position and status, aiding in commissioning and troubleshooting.
The following table details the primary technical data for the 3TH2031-0HY4 contactor relay.

The SIEMENS 3TH2031-0HY4 is a fundamental component in a wide array of electrical control environments.
Machine Control Panels: Used as an interface relay to multiply output signals from a PLC, controlling solenoid valves, small motors, or other contactor coils.
Interlocking and Safety Circuits: Implementing electrical interlocks between machine functions to ensure safe operating sequences.
Building Automation: Switching control circuits for lighting groups, ventilation fans, or heating elements in commercial buildings.
Control Circuit Expansion: Adding extra switching capacity to timers, thermostats, or control switches.
Signal Isolation: Separating control circuits of different voltage levels or providing galvanic isolation for sensitive electronic controls.
The Sirius 3TH series, including the 3TH2031-0HY4, is synonymous with reliability and durability. Its robust construction ensures stable performance over millions of switching cycles, even in demanding industrial environments with vibration and temperature fluctuations. The universal coil voltage eliminates the need for separate AC and DC relay stocks, reducing complexity. Furthermore, its compatibility with the wider Sirius system of accessories, such as auxiliary contact blocks and timers, allows for easy customization and expansion of functionality to meet specific application needs. This makes it a cost-effective and future-proof choice for system designers and panel builders.
The SIEMENS 3TH2031-0HY4 contactor relay is a quintessential component for efficient and reliable control circuit design. Its four-pole configuration, universal coil, and proven Sirius quality make it an indispensable tool for engineers building control panels across manufacturing, infrastructure, and automation sectors. By providing dependable switching performance, it forms a critical link in the chain of command that brings automated systems to life, ensuring that control logic is accurately translated into physical action.



