What percent demand factor is applied to the unbalanced neutral feeder load in excess of 200 amps?

In electrical design, the demand factor is a crucial concept used to estimate the load that will actually be drawn from a feeder compared to the total connected load. When dealing with unbalanced loads, especially in three-phase systems, it is essential to understand how to apply the demand factor to the neutral conductor, which can carry significant current if the loads across the phases are not equal.

For feeder loads exceeding 200 amps, a demand factor of 70 percent is applied to account for the unbalanced nature of the load. This means that rather than assuming the full capacity of the system will be utilized (which is often not the case in practical scenarios given that not all connected devices operate at peak demand simultaneously), the demand factor effectively reduces the load calculation. By applying a 70 percent demand factor, designers ensure that the system isn't oversized, which optimizes material use and ensures safety and efficiency within the installation.

This practice aligns with electrical codes and design standards, which recognize that certain levels of unbalance can lead to higher currents in the neutral, thus refining the way loads are calculated helps to mitigate potential issues such as overheating or safety hazards in unbalanced electrical systems.