Introduction to MX+OF Shunt Trip Units

The Shunt release MX+OF circuit breaker accessories trip unit is an integral component in modern electrical systems, offering enhanced safety and operational efficiency. This device combines the shunt trip functionality (MX) with auxiliary contact features (OF), providing both remote tripping capabilities and status indication for circuit breakers. Designed for seamless integration with miniature circuit breakers, the MX+OF unit is pivotal in managing electrical circuits effectively.

MX+OF Usage Scope

The MX+OF unit is tailored for AC circuits with frequencies of 50Hz or 60Hz and a rated voltage up to 400V. It is compatible with both miniature and multi-pole circuit breakers, facilitating remote operations and offering clear status indications. This versatility makes it suitable for a wide range of applications, from residential safety enhancements to industrial power management.

Operating and Installation Conditions

The MX+OF unit thrives under specific conditions: ambient temperatures from -5℃ to +40℃, with an altitude not exceeding 2000 meters, and relative humidity manageable up to 90% during the wettest months. These parameters ensure reliable operation across various environments, from dry, temperate climates to more humid settings.

Technical Performance and Parameters

With a rated insulation voltage of 500V and control supply voltages of AC 230 and 400V, the MX+OF unit is designed for robust performance. Its operational reliability spans from 70% to 110% of the rated control supply voltage, guaranteeing the circuit breaker’s effective tripping when necessary. The unit’s lifecycle supports no less than 10,000 operational cycles, underlining its durability and reliability.

Main Working Principle

The MX+OF unit operates by integrating a tripping mechanism with an electromagnetic system and auxiliary contacts. This design ensures that when the circuit breaker is engaged, the MX+OF unit simultaneously indicates the status and allows for remote control tripping, enhancing both safety and convenience.

Mx Of


Wiring the MX+OF Unit

Wiring the MX+OF unit requires careful attention to detail. Connections are made to terminals C1 and C2 for remote control functionalities, with specific terminals dedicated to indicating the breaker’s status (C2-14 for normally closed and C2-12 for normally open contacts). Correct wiring is crucial to avoid damage and ensure the unit’s proper functioning.

Installation, Use, and Maintenance

Before installation, verify that the MX+OF’s specifications match the operational conditions of your system. Installation involves aligning and securing the unit to the circuit breaker, ensuring a snug fit. Regular maintenance should focus on verifying connections and operational reliability, with any issues addressed promptly to maintain safety and efficiency.

Key Precautions

When installing and operating the MX+OF unit, it’s vital to ensure correct wiring to prevent damage. Connections should be secure, with all screws tightly fastened to avoid any loose contacts, which could lead to operational failures or safety hazards.


The MX+OF shunt trip unit represents a significant advancement in electrical safety and functionality. By understanding its working principles, installation requirements, and maintenance practices, professionals can enhance the safety, efficiency, and reliability of electrical systems. Following the guidelines and precautions outlined ensures that the MX+OF unit will provide optimal performance and safety for its intended lifespan.