What is the ampacity for conductors installed open in free air with an ambient temperature of 40°C, when using Table 310.19?

To determine the correct ampacity for conductors installed in free air at an ambient temperature of 40°C using Table 310.19, it is important to consider how conductor ampacity is affected by installation method and temperature.

Table 310.19 provides ampacity ratings for various conductors under different conditions. When conductors are installed open in free air, their ability to dissipate heat improves compared to being in conduit or insulated bundles, which allows them to carry more current.

At an ambient temperature of 40°C, it is essential to refer to the correct column of Table 310.19 that specifies ratings for conductors in free air. In this case, the table indicates that for common conductor sizes, the ampacity can significantly increase. The selection of 198 A aligns with the ratings provided for typical conductor sizes when accurately taking into account the installation conditions and temperature adjustments.

Choosing 198 A indicates a recognition of the increased capacity afforded by free air installation and the specific ambient conditions, highlighting the importance of consulting the code tables correctly to ensure compliance with the National Electrical Code. This emphasizes the need for a structured approach to code calculations, ensuring safety and reliability in electrical installations.