Washington Administrative Code(WAC) and Revised Code of Washington (RCW) Electrical Practice Exam

What is the required ground resistance for rod, pipe, or plate electrodes?

1. 10 ohms or less

2. 15 ohms or less

3. 25 ohms or less

4. 30 ohms or less

The correct answer is: 25 ohms or less

The correct requirement for ground resistance for rod, pipe, or plate electrodes is 25 ohms or less. This standard is established to ensure adequate grounding for electrical systems, which enhances safety by minimizing the risk of electrical shock and reducing the potential for damage during fault conditions. The 25-ohm threshold is significant because it provides a guideline for effective grounding. Lower resistance enables more efficient dissipation of fault currents into the ground, facilitating the operation of protective devices like circuit breakers and fuses. When grounding systems have lower resistance, it offers improved protection for both equipment and personnel. Understanding this requirement is crucial for ensuring compliance with safety codes and standards, specifically those outlined in the National Electrical Code (NEC) and corresponding local regulations. The choice of a threshold such as 25 ohms reflects a balance between achieving effective grounding and practical implementation of grounding methods in various environments.