ABYC Marine Electrical Practice Exam

What is the maximum allowable resistance on a grounding conductor?

1. 1 ohm

2. 0.5 ohms

3. 0.25 ohms

4. 0.75 ohms

The correct answer is: 0.25 ohms

The maximum allowable resistance on a grounding conductor is set to ensure that the grounding system functions effectively in case of a fault, which can help protect both equipment and individuals from electrical hazards. A resistance value of 0.25 ohms is recognized as an optimal standard for marine electrical systems. This low resistance threshold helps ensure that fault currents can pass through the grounding conductor quickly and safely to ground, minimizing the risk of electric shock or fire. When resistance is too high, it could impede the flow of electrical current during a fault condition, potentially allowing dangerous voltages to persist on equipment and increasing the risk of electrical shock. The value of 0.25 ohms is aligned with industry standards and regulations to promote safety and performance in marine environments where electrical systems are subject to wet and corrosive conditions. Higher resistance levels, such as those proposed in the other options, would not provide the same level of safety during fault conditions. Thus, maintaining a grounding conductor resistance of no more than 0.25 ohms is critical for the reliable operation of any marine electrical system.