NEC Y6XC24 PCB

The demand factor is the ratio of the maximum demand of the system (or portion thereof) and thetotal connected load. This value is always less than one.

This is not to be confused with thediversity factor, which is not found in the NEC—instead it is found in the IEC61439(Low VoltageSwitchgear and Control Gear Assemblies),

and is used in electrical switchgear designs outside thepurview of the NEC.Think of this as the requirements for industrial low voltage assemblies.

The diversity factor is the ratio of the sum of the individual maximum demand of the systems tothe total connected load.The diversity factor is greater than or equal to one.

The distinction is ademand factor is time independent (and conservative), which results in the need for larger wires—and thus is the standard in the NEC.The diversity

factor accounts for time, meaning,not all themaximum loads will occur at the same time. So, for example, an 80% diversity means a device orsubsystem operates at its

maximum 80% of the time it is turned on.Residential loads have thehighest diversity factors while industrial systems generally have the lowest.

When performing feeder calculations with the NEC, the load is multiplied by the demand factorlowering the overall wiring size. When performing feeder calculations

for feeders upstream of theservice entrance panel to a residence or in and industrial facility for switchgear assemblies, theload is divided by the diversity factor to lower the overall wiring size.