Which of the following is NOT an approved method for coupling ground rods together for deeper grounding?

The reason that tie wire is not considered an approved method for coupling ground rods together for deeper grounding lies in its insufficient reliability and electrical conductivity. Grounding systems must maintain a low-resistance path to earth to effectively dissipate lightning strikes or fault currents, which is critical for safety.

Welding, exothermic bonding, and wrap-around connectors provide robust connections that reduce resistance and enhance the integrity of the grounding system. Welding creates a continuous metal bond that can handle high currents without introducing significant resistance. Exothermic bonding uses a chemical reaction to create a strong metallic bond between materials, while wrap-around connectors securely fasten ground rods with minimal resistance.

In contrast, tie wire may not provide a solid and secure electrical connection capable of withstanding high-energy events, leading to potential points of failure in the grounding system. Hence, manual alternatives like tie wire are discouraged when creating reliable grounding systems.