The grounding wire of a distribution box should be connected to the designated PE or grounding terminal inside the box, ensuring a secure and low-resistance path to the main ground.

Identifying the Grounding Terminal

Inside a distribution box, the grounding input terminal is typically marked with PE (Protective Earth) or a grounding symbol. This terminal may be part of a grounding bar or a dedicated grounding stud attached to the metal backpanel of the enclosure ( ). The terminal serves as the main connection point for the incoming ground wire from the power supply and for grounding internal components.

Connecting the Ground Wire

1. Select the appropriate wire: Use a yellow-green insulated copper wire with a cross-sectional area meeting local standards (e.g., 10 AWG in the US or 6 mm² elsewhere) ( ).
2. Prepare the wire: Strip the insulation for the required length to expose the copper conductor.
3. Attach to the terminal: Insert the stripped wire into the PE terminal or grounding bar and tighten the screw securely to ensure a firm connection ( ).
4. Ground internal components: If the distribution box contains electrical components that require grounding, connect them to the same PE bar using copper wires to maintain a continuous grounding path ( ).

Ensuring Proper Grounding

• The ground resistance between all system parts should be less than 0.1 Ohm to ensure safety ( ).
• For metal enclosures, the PE bar or grounding terminal should be bonded to the enclosure backpanel, and doors or removable panels should have independent bonding jumpers to maintain continuity ( ).
• Clearly label all grounding connections for inspection and maintenance purposes ( ).

Optional Enhancements

• Grounding terminal blocks can be used instead of studs or lugs. These blocks clamp onto a DIN rail and distribute ground potential to multiple terminals efficiently ( ).
• In complex systems with multiple spindles or long tool cables, additional grounding wires may be added between mounting plates and components to reduce total resistance ( ).

By following these steps, the distribution box will have a reliable and safe grounding system, protecting both equipment and personnel from electrical faults.