What is the ampacity rating for a 250 kcmil THHN copper conductor at 101 degrees Fahrenheit?

To determine the ampacity rating of a 250 kcmil THHN copper conductor at 101 degrees Fahrenheit, one must refer to the NEC (National Electrical Code) or ampacity charts that provide specific ratings based on conductor size, insulation type, and ambient temperature.

For a 250 kcmil type THHN copper conductor, the standard ampacity under typical conditions—such as an ambient temperature of 86 degrees Fahrenheit (the standard reference temperature)—is generally around 260 to 270 amperes. However, when operating in a warmer environment, adjustments must be made due to the decrease in ampacity with increasing temperature.

At 101 degrees Fahrenheit, the ampacity is adjusted based on correction factors. Generally, if we apply the appropriate correction factor for this specific temperature, it results in an ampacity rating that is slightly lower than the value at the standard temperature. This adjustment leads to the ampacity rating approximating the value of 263.9 amperes, making it the most accurate answer among the options provided.

Understanding the diagrammatically expressed ampacity ratings and the associated temperature adjustments is crucial when dealing with electrical load calculations, as it ensures the safe and efficient use of conductors in various temperature conditions.