Each distribution box must be grounded using appropriately sized wires connected from the housing to the mounting plate and then to the central grounding point, ensuring total resistance below 0.1 Ohm.

Grounding Procedure

1. Qualified Installation Grounding must be performed by a qualified electrician to ensure safety and compliance with local regulations .
2. Wire Sizing
   • US market: Use a 5.26 mm² (10 AWG) ground wire from the distribution box to the mounting plate.
   • Other markets: Use a 6 mm² ground wire .
   • For connections between the mounting plate and spindle plate, use a 16 mm² wire (US: 13.29 mm², 6 AWG) to maintain low resistance, especially for long tool cables or multiple spindles .
3. Connection Points
   • Attach a ground wire from a threaded stud at the bottom of the distribution box housing to the mounting plate.
   • Connect a second ground wire from the mounting plate to the factory central grounding point .
4. Resistance Requirements
   • The total ground resistance between all system parts must be less than 0.1 Ohm.
   • For long tool cables, calculate the combined resistance of the tool cable and ground wire in parallel to ensure it remains below the threshold. For example, a 60 m tool cable with 3 mOhm/m resistance and a 6 AWG ground wire with 1.4 mOhm/m results in a total resistance of 57 mOhm, which is acceptable .
5. Alternative Configurations
   • In some applications, the extra ground wire between the mounting plate and spindle plate can be omitted if the tool cable resistance is sufficiently low .

Best Practices

• Use high-quality copper or copper-bonded steel wires to prevent corrosion and maintain long-term conductivity .
• Test the grounding system after installation to verify resistance is within limits.
• Ensure all metallic parts of the distribution box and connected equipment are bonded to the same grounding network to prevent potential differences and electrical hazards . Following these steps ensures personnel safety, equipment protection, and compliance with electrical standards for distribution box installations.