Electrical Inspection, Testing and Certification Practice Exam

In assessment of insulation resistance, what minimum value is generally acceptable?

1. 1 Mohm

2. 1.5 Mohm

3. 2 Mohm

4. Megohm varies by installation

The correct answer is: Megohm varies by installation

The minimum acceptable insulation resistance value can vary significantly depending on the specific installation type, conditions, and regulatory standards that apply to that installation. Different systems and environments may necessitate different minimum resistance requirements to ensure safety and proper operation. For instance, electrical systems in industrial settings might require higher insulation resistance values compared to residential systems. Additionally, different types of equipment and their exposure to environmental factors, such as moisture or conductive contaminants, will also influence the insulative properties required for safe operation. National and international standards, such as those from the Institute of Electrical and Electronics Engineers (IEEE) or the National Electrical Code (NEC), provide guidelines for acceptable insulation resistance values, but these are not one-size-fits-all. Therefore, it’s crucial to refer to the specific standards and regulations that pertain to the given installation to determine the appropriate insulation resistance value for that context. This flexibility underscores the importance of tailoring assessments to individual circumstances, making the assertion that the acceptable value can vary widely a critical understanding in electrical inspection and testing.