When can farm loads be combined into a single load for calculation purposes?

Combining farm loads into a single load for calculation purposes is permissible when the loads have the same function. This allows for a more efficient calculation of the total load demand since these similar loads may operate in tandem and have similar electrical characteristics. For instance, if multiple pieces of equipment perform the same task, such as irrigation pumps, they can be assessed together to simplify the calculation and ensure that the electrical system is adequately sized to handle the combined load without unnecessary complexity.

This approach aligns with the NEC's provisions aimed at simplifying calculations and ensuring safety without compromising the effectiveness of the electrical system. The other answers introduce different conditions that may not necessarily ensure the same operational load characteristics, making them less relevant for combining loads effectively.