When there are four or more appliances fastened in place, which demand factor shall be applied to the appliances?

When four or more appliances are fastened in place, the appropriate demand factor to apply is 75%. This reduction acknowledges the fact that when multiple appliances are used simultaneously, they do not typically operate at their full rated capacity at the same time.

This concept is based on the principle of demand factors outlined in the National Electrical Code (NEC), which allows for a more efficient and accurate calculation of the load that a system needs to be designed to handle. By applying a 75% demand factor, it recognizes that the combined load of all appliances will be less than the sum of their individual capacities, providing a more realistic approach to calculating service requirements, and ensuring the system is not oversized unnecessarily.

Applying this demand factor helps in calculating the maximum load that will practically be experienced in a given installation, which is particularly important in preventing overloading circuits and ensuring the safety and efficiency of electrical systems.