Question

When performing infrared thermography on an electrical distribution panel, what does a localized hot spot on a single phase lug suggest regarding the mechanical integrity of the connection?

Accepted Answer

A localized hot spot on a single phase lug strongly suggests an increase in electrical resistance at that specific connection point, typically caused by a mechanical failure such as a loose terminal or corroded contact surface. This resistance causes electrical current to dissipate energy as heat rather than flowing through the conductor, similar to how a kink in a garden hose creates pressure and friction that slows down water flow. In this case, the connection has lost its mechanical integrity, meaning the hardware is no longer holding the wire firmly enough to provide a secure, low-resistance path for the electricity. If the lug is loose, the resulting microscopic air gaps between the wire and the terminal force the current through a smaller physical area, causing the metal to heat up significantly. This creates a dangerous cycle where the heat causes the metal to expand and then contract as it cools, further loosening the connection and increasing the resistance, which eventually leads to arcing or a total thermal failure of the component.

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When performing infrared thermography on an electrical distribution panel, what does a localized hot spot on a single phase lug suggest regarding the mechanical integrity of the connection?

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