When performing voltage drop calculations, you can set how the voltage drop is calculated for transformers. Typically, this option is set depending upon how and whether you decide to account for voltage drop by making changes to the system.
For Design Master Electrical RT in Revit, the option is set in the Voltage Drop section of the Project Options command. For Design Master Electrical in AutoCAD, the option is set in the Distribution Equipment section of the Options command.
There are three settings available:
Include transformers in voltage drop
The voltage drop through the transformer will be calculated and added to the voltage drop through the upstream feeders.
This option is the most complete calculation available; however, including the voltage drop through the transformer results in values that typically exceed the recommendations given in the NEC.
The other options allow you to approximate adjusting the taps on the transformers to account for the voltage drop.
The voltage drop through the transformer will be ignored when the voltage drop for the system is calculated. The voltage drop through the upstream feeders is carried through the transformer.
This option assumes the taps on the transformer are adjusted to account for just the voltage drop through the transformer itself. The voltage drop in the system will still include all of the feeders.
Reset voltage drop at transformers
The voltage drop will be set to zero at each transformer. The voltage drop through the transformer and upstream feeders is ignored.
This option assumes the taps on the transformer are adjusted to account for both the voltage drop through the transformer and the voltage drop through the feeders to the transformer.