The grounding resistance of an optical distribution box should not exceed 5 ohms under typical conditions, and 1 ohm for highly sensitive or comprehensive communication installations.

Recommended Values

• Ordinary communication offices: The grounding resistance should be less than 5 ohms to ensure adequate protection of equipment and personnel .
• Comprehensive communication buildings or sensitive installations: The grounding resistance should be 1 ohm or less to provide optimal safety and minimize potential differences .
• High earth resistance areas: In regions with poor soil conductivity, resistance may be allowed up to 10 ohms, but additional grounding measures are recommended .

Practical Implementation

• All metallic components of the optical distribution box, including doors and panels, should be properly bonded to the grounding system using copper conductors with sufficient cross-sectional area (typically ≥ 1.6 sq. mm for cabinet connections and ≥ 25 sq. mm for main grounding conductors), .
• Conductive fiber optic cables must be bonded to the building's grounding electrode system, preferably via a dedicated bonding conductor connected to the Telecommunications Main Grounding Busbar (TMGB) or Central Office Ground Busbar (COG Busbar), .
• The grounding conductor should be as short and direct as possible, ideally less than 20 feet, to reduce impedance and ensure effective fault current dissipation .

Standards and Compliance

• The NEC 770.100 and ANSI/TIA-568-C.0 / J-STD-607-A standards require that metallic components of fiber optic systems be bonded to the building grounding system to maintain continuity and safety .
• Achieving a grounding resistance of ≤ 5 ohms is generally feasible in typical office or telecommunication environments, while ≤ 1 ohm is recommended for critical or high-risk installations . By adhering to these guidelines, the optical distribution box will maintain proper grounding, reduce the risk of electrical hazards, and comply with industry standards.