Home Inspection State Practice Exam

What is the most probable cause of melted insulation on a neutral conductor in a sub panel?

1. The neutral conductor is overloaded.

2. Inadequate grounding.

3. The neutral conductor is loose at the terminal bar.

4. The circuit is undersized.

The correct answer is: The neutral conductor is loose at the terminal bar.

The scenario of melted insulation on a neutral conductor in a sub-panel is most likely caused by a loose connection at the terminal bar. When a neutral conductor is not securely fastened, it can lead to high resistance at the connection point. This high resistance generates excess heat due to the electrical current that passes through the point of contact. As the heat builds up, it can melt the insulation surrounding the conductor. This is particularly critical in a sub-panel, where it is essential for all connections to be tight and secure to ensure proper current flow and to prevent hazardous conditions. Loose connections can often go undetected until they cause noticeable issues such as overheating or even electrical fires. While other choices present potential concerns, they do not specifically explain the melting of insulation in the same way that a loose connection does. Overloading the neutral conductor can lead to current overload, but typically the insulation would not melt in that case unless the neutral was not adequately sized or another factor was compounding the issue. Similarly, inadequate grounding would pose a different set of problems and wouldn't directly cause the insulation of a neutral conductor to melt. Circuit size plays a role in overall load management but does not singularly indicate why insulation would melt on a neutral.