underground concrete electrical pull box

The following is a professional analysis of the **Underground Concrete Electrical Pull Box**, combining industry standards,

 product features, and installation key points:

 I. Core Definitions and Functions

The **Underground Concrete Electrical Pull Box** is an electrical connection device **buried underground or in a concrete structure**

, which is used to protect wire and cable joints, provide access for maintenance, and meet the requirements of **waterproofing, 

compression resistance, and corrosion resistance**. Its core functions include:

- **Protection Function**: Resist the influence of external environmental factors such as groundwater, soil corrosion, and mechanical

 pressure.

- **Convenience for Maintenance**: The modular design facilitates the later maintenance and expansion of the electrical lines.

- **Structural Adaptability**: It can be pre-embedded in concrete walls, floors, or directly buried in the ground, and supports both 

surface-mounted and recessed installations.

 II. Classification and Typical Products

1. Classification by Material

2. Examples of Mainstream Products

1. **Protection Rating**

   - General scenarios: **IP66** (Resistant to water jets);

   - Long-term damp or buried environments: **IP68** (Continuous submersible level, for example, DATA-E003 can withstand 

a water pressure of 0.4MPa for 72 hours).

2. **Compression Strength**

   - For concrete materials: In **non-traffic areas**, it should be ≥2000 psi, and for **roadway areas**, a **load-bearing type** 

needs to be customized (such as Oldcastle products).

3. **Sealing Design**

   - **Threaded compression + Silicone ring**: The box cover and the box body are fixed by threads, with a built-in double-curved 

surface silicone ring (such as the patented pull box);

   - **Epoxy resin potting**: Fill the cable entry with epoxy resin to prevent water seepage;

   - **Airtight rib structure**: In civil air defense scenarios, an **airtight rib** (with a thickness ≥3mm) needs to be welded to block 

capillary gaps (refer to the GB 50038 civil air defense specification).

 IV. Installation Process and Precautions

1. Pre-embedded Installation (Mainstream Method)

1. **Positioning and Fixing**

   - Fix it before the concrete is poured: Fix it to the formwork with a steel bar bracket or iron nails, and the elevation should be 

**1cm higher** than the design value (to avoid sinking during pouring).

   - Connect the pull box and the electrical conduit: Use a **wedge-shaped straight-through joint** (patented design) or a 

**waterproof gland** to reduce the impact of bends on the structure.

2. **Sealing Process**

   - Fill the gap between the electrical conduit and the pull box with **sealing putty** (such as polysulfide sealing paste);

   - For civil air defense projects, a **3mm hot-dip galvanized protective cover** needs to be added, and after tightening the bolts,

 seal it with epoxy putty.

3. **Grounding Requirements**

   - The metal pull box needs to be reliably connected to the **main grounding conductor**. The diameter of the welded round 

steel should be ≥6mm, or a special grounding clip can be used.

2. Later Installation (For Formed Concrete)

- **Surface-mounted Method**: Fix it to the wall with expansion bolts, and place a **waterproof rubber pad** between the cover 

and the wall;

- **Grooving Limitations**: The grooving depth in load-bearing walls should be ≤1/4 of the wall thickness. It is preferred to operate

 within the plaster layer (with a thickness ≥5cm), and the depth of the bottom box should be ≤3.8cm.

V. Typical Application Scenarios

1. **Municipal Engineering**: Underground cable branching, streetlight power distribution;

2. **Civil Air Defense Projects**: Sealing of electrical pipelines passing through protective walls (Needs to comply with the GB 

50038-2005 civil air defense specification);

3. **Sewage Treatment**: Wiring of underwater sensors, control of submersible pumps;

4. **Building Power Distribution**: Protection of recessed electrical lines in concrete floors/columns.

VI. Purchase Suggestions

1. **Selection According to the Environment**

   - Damp but without water pressure: **Plastic pull box** (IP68, such as DATA-E003);

   - Buried or load-bearing scenarios: **Concrete/Hot-dip galvanized steel** (such as Oldcastle, Hubbell);

   - Civil air defense/Explosion-proof scenarios: **Hot-dip galvanized steel + Airtight rib** (Needs to provide civil air defense 

certification).

2. **Selection According to Functions**

   - Requiring frequent maintenance: **Quick-lock cover** (such as Hubbell);

   - Multiple cable access: **Expandable interface** (Standard configuration with 2 holes, up to 4 holes at most).

VII. Conclusion

The core of the underground concrete electrical pull box lies in its **waterproof and airtight performance** and **structural 

adaptability**. During pre-embedded installation, the positioning and sealing process needs to be strictly controlled, and in civil 

air defense scenarios, additional requirements for protection and airtightness need to be met. In terms of brand selection, 

Oldcastle's concrete products are suitable for municipal engineering, Tangshan Pingsheng's IP68 plastic box is suitable for 

damp environments, and for civil air defense projects, the hot-dip galvanized steel material should be identified and the

 national standard certification should be verified.