ICC Residential Electrical Inspectors Practice Exam

How is the unbalanced load percentage calculated for feeder neutral loads in specific household appliances?

1. By summing all appliance ratings

2. By considering maximum load on all appliances

3. By using a standard percentage

4. By calculating based on the highest rated appliance

The correct answer is: By calculating based on the highest rated appliance

The calculation of unbalanced load percentage for feeder neutral loads focuses on the highest rated appliance because it provides a benchmark for the maximum potential current that the neutral conductor may have to carry. When balancing loads, the neutral conductor often carries the imbalance between the phases in a three-phase system. In a residential setting, where single-phase systems are more common, the highest rated appliance helps determine the worst-case scenario for current flow in the neutral. This is crucial because the neutral conductor is designed to handle the difference in loads across different phases. By specifically calculating based on the highest rated appliance, the assessment accounts for situations where one appliance may draw significantly more current than others. This ensures that the neutral is adequately sized to handle these peak loads without being overloaded. In contrast, summing all appliance ratings or considering maximum load on all appliances could lead to a misunderstanding of how the loads actually interact. Using a standard percentage may not adequately reflect the unique characteristics of the specific household configuration or appliances involved. Thus, focusing on the highest rated appliance provides a more accurate and practical approach for evaluating and ensuring the safety and effectiveness of the electrical system.