Which of the following voltages are nominal system voltages specified for use in calculations by the Code?

In the context of electrical systems and codes, nominal system voltages refer to the standard voltage levels that are used as references for electrical calculations, design, and equipment ratings. These nominal voltages provide a basis for sizing equipment and verifying that installations comply with safety standards and regulations.

480 V is a commonly used nominal system voltage for industrial three-phase systems. It is a standard voltage for many motors and industrial applications, making it a critical voltage level in electrical engineering and installations. Because of its prevalence in industrial settings, the Code recognizes it as an appropriate reference voltage for calculations related to the design and implementation of electrical systems.

On the other hand, while 120 V and 220 V are also utilized in various applications, including residential and small commercial settings, they do not have the same level of specification for industrial calculations within the Code as 480 V does. The inclusion of 135 V does not align with typical nominal system voltages recognized for broad applications.

The designation of 480 V as a nominal system voltage highlights its significance in electrical calculations and ensures that equipment and installations are designed effectively to handle the operational demands of industrial environments.