Which of the following reflects a correct ampacity calculation for three current-carrying conductors?

To determine the correct ampacity calculation for three current-carrying conductors, it's essential to understand the derating factors that apply when multiple conductors are bundled together. The ampacity of a conductor is typically reduced due to the increase in temperature that results from having multiple conductors carrying current close together.

In this context, the calculations provided represent the original ampacity values for the conductors, adjusted by a derating factor. The calculation begins with the nominal current that the conductors can handle, which is then multiplied by the corresponding derating factor.

Choosing the first option is correct because it accurately applies the derating factor of 0.58 to the original ampacity of 225 amps. The product, 130.5 amps, reflects the adjusted capacity considering the situation of having three conductors. This results in a safe and acceptable ampacity level under those conditions.

Each of the other calculations uses different initial values and derating factors, which may not align correctly with established ampacity tables or principles. Therefore, the first option stands out as the one that follows the principles of ampacity calculations correctly.