Journeyman Electrician Practice Exam

How is the ampacity of conductors affected in a raceway with multiple conductors?

1. Increases due to heat dissipation

2. Reduces due to heat accumulation

3. Remains unchanged

4. Varies based on conductor size

The correct answer is: Reduces due to heat accumulation

The ampacity of conductors in a raceway with multiple conductors reduces due to heat accumulation. When multiple conductors are placed in close proximity within a raceway, they generate heat as they carry current. Each conductor produces heat, and the confined space of the raceway impedes the ability of that heat to dissipate effectively. This buildup of heat can cause the conductors to exceed their rated capacity, leading to potential overheating and increased risks of insulation degradation or failure. Standards and codes often take this into account, specifying derating factors to provide guidance on how much current can safely flow through conductors when they are bundled together. Therefore, the presence of multiple conductors leads to a situation where the total allowable current (ampacity) must be reduced to ensure safety and reliability in electrical systems. This is why heat accumulation is a critical factor when considering the ampacity of conductors in such arrangements.