metal electrical box reducer bushing

The following is a professional analysis of the **Metal Electrical Box Reducer Bushing**, combined with electrical installation specifications and practical applications:

 I. Definition and Core Functions

The **Metal Reducer Bushing** is a fitting used for **connecting metal conduits of different diameters** (such as Rigid Metal Conduit (RMC) and Intermediate Metal Conduit (IMC)). Its core functions include:

1. **Diameter Transition**: Achieve threaded connection of two conduits with different diameters (for example, transitioning from a 1.5-inch conduit to a 1-inch one);

2. **Cable Protection**: Provide a smooth inner surface to prevent cables from being scratched by sharp edges when passing through the conduit;

3. **Sealing and Protection**: Work with sealing rings or sealants to meet the requirements of protection ratings such as **IP54/IP66**;

4. **Grounding Continuity**: The metal material can conduct grounding current to ensure reliable grounding of the system.

 II. Types and Typical Applications

1. Classification by Structure

2. Classification by Standard

III. Key Technical Parameters

2. Classification by Standard

III. Key Technical Parameters

 IV. Installation Specifications and Key Points

1. Thread Matching

- It is necessary to fully match the **NPT threads** of the conduit (for example, an external 1/2" NPT thread with an internal 

3/4" NPT thread) to avoid loosening;

- It is recommended to use **thread sealing tape** (such as Teflon tape) to enhance the sealing performance.

2. Grounding Requirements

- The metal bushing needs to be reliably connected to the **PE busbar of the box** or the **conduit grounding system**, 

and the grounding resistance ≤ 4Ω;

- The bushing with a grounding plate can be directly fixed to the grounding post of the box with bolts.

3. Environmental Adaptation

- **Outdoor/Wet Environment**: Select materials such as **galvanized steel + sealing ring** or **316 stainless steel** to 

prevent corrosion;

- **High-temperature Environment**: Avoid using plastic bushings, and preferentially select metal materials (with a

 temperature resistance ≥ 150℃).

 V. Key Technical Points for Purchase

1. **Size Compatibility**:

   - Clearly define the conduit type (RMC/IMC) and diameter (such as Trade Size 1/2"~4");

   - Example: To connect a 3/4" IMC conduit to a 1/2" knockout hole of the box, a **3/4"→1/2" reducer bushing** needs to be selected.

2. **Certification Compliance**:

   - For projects in North America, products with **UL certification** (such as Halex, Orbit Industries) need to be selected;

   - For domestic projects, they need to comply with **GB/T 14823.1** (Standard for Metal Conduit Fittings).

3. **Additional Functions**:

   - Give priority to bushings with **anti-slip serrations** to prevent slipping during installation;

   - **Insulated bushings** (with a plastic sleeve inside) can be selected to isolate the metal conduit from the cables.

 VI. Recommendations for Typical Products

 VII. Common Errors and Solutions

 Conclusion

The metal reducer bushing is a key fitting for connecting the electrical box and the conduit. Its core functions are **diameter 

transition, sealing, and grounding**. When purchasing, attention should be paid to **diameter matching, material anti-corrosion,

 and certification compliance**. During installation, strictly follow the thread sealing and grounding specifications to ensure the 

safety and reliability of the system.