In a residential system, which statement best distinguishes grounding from bonding?

• A. Bonding provides a reference to earth for the system, and grounding connects exposed metallic parts to maintain a safe, equal potential.
• B. Grounding bonds the building steel to the neutral conductor.
• C. Grounding and bonding both refer to protective coatings.
• D. Grounding provides a reference to earth for the system, while bonding connects exposed metallic parts to maintain a safe, equal potential.

Answer: (D)

Grounding and bonding serve different safety roles in a residential electrical system. Grounding establishes a reference to earth for the electrical system, giving a stable voltage reference and providing a path for fault current and lightning to dissipate into the earth. Bonding, on the other hand, ties together exposed metallic parts—such as water pipes, gas piping, and enclosures—so they are at the same electrical potential, minimizing shock risk if a fault occurs.

That’s why the best statement is the one that says grounding provides a reference to earth for the system, while bonding connects exposed metallic parts to maintain a safe, equal potential. In practice, the grounding conductor links the service equipment to a grounding electrode, and bonding ensures all conductive metal items are connected to that same network to prevent dangerous voltage differences. The other options either mix up these roles or reference concepts (like protective coatings) that aren’t about grounding or bonding.