NEMA Symbology: Electrical Classification for the North American Market - Blog

In today's article, we explore what there is to know about NEMA symbology by analyzing its distinctive characteristics.
Specifically, we see how it fits into the context of SPAC Automazione 2024, the professional CAD designed for the industrial sector.
In a world where each continent regulates its own electrical products with specific standards, the National Electrical Manufacturers Association (NEMA) plays a fundamental role by providing guidelines and standards for the North American market.

What is the National Electrical Manufacturers Association (NEMA)?

The National Electrical Manufacturers Association (NEMA) represents the national association of U.S. electrical manufacturers, located near Washington D.C.
Founded in 1926, it consists of about 450 companies. Additionally, the NEMA Board of Governors is composed of thirty high-level corporate executives, elected by the general members for a three-year term. This board is organized into policy committees, which guide the organization's various operations.
The association publishes over 1000 standards and technical documents in the electrical field, facilitating collaboration between manufacturers and users of electrical equipment.

NEMA Graphic Standard: Some Details to Know

The NEMA graphic standard constitutes a standardized system of graphic representation, designed to clearly outline elements within electrical diagrams.

In addition to facilitating understanding, these symbols represent a series of unique characteristics that contribute to defining the specificity of each element, adding value to the entire design process.

Below are some aspects of the graphic representation of NEMA diagrams for electrical installations:

• Drawing conventions: follow specific schemes. For example, circuits are often drawn so that current flow goes from top to bottom or from left to right.
• Conductor identification: NEMA specifies a system of coloring and markings to recognize conductors. This includes the use of specific colors for cables and wires: line and load circuits (AC and DC), power circuits, and motor circuits are black. Control circuits foresee AC in red and DC in blue.
• Component labeling: each is clearly classified with a reference number or letter. This labeling helps uniquely identify each component and simplifies the understanding of the diagram.

This series of symbols translates into a common language, facilitating both electrical engineers and technicians in the interpretation and design of electrical systems in full compliance with NEMA standards.

Key Differences Between NEMA and IEC Symbology

Protecting electrical enclosures from dust and moisture is an important aspect. Therefore, gaining a full understanding of the differences between the IEC (International Electrotechnical Commission) and NEMA (National Electrical Manufacturers Association) classifications becomes necessary.
The IEC classification is predominant in Europe and Asia, while NEMA is widely adopted in the United States. The differences between NEMA and IEC clearly emerge when examining symbology, contact designation, device sizes, and marking approach. Let's look at them together:

• NEMA contacts are often designated with letters or numbers following the NEMA 250 standard. Devices can vary significantly in size and shape based on specific applications. Moreover, North American symbols tend to be more detailed and specific, including details on the construction and physical configuration of the device.
• The IEC classification is based on numbers from 1 to 11 standardized to indicate the level of protection against hazardous parts and water ingress. This methodology, with uniform shapes to facilitate global installation, focuses on functionality, using stylized and simplified symbols instead of physical details.

In conclusion, choosing between NEMA and IEC requires attention to local specifications and safety regulations.

IEC-NEMA Conversion with SPAC Automazione 2024: The Key to Compliant Electrical Schematics

To support those who need to generate electrical documentation for North America, SPAC Automazione 2024 has fully integrated the NEMA graphic standard, making electrical schematics compliant with these standards, particularly the UL regulation.

The process of modifying and transforming an electrical schematic made with IEC symbology is straightforward. If schematics with IEC symbols have already been produced, SPAC Automation 2024 does not automatically perform the conversion. However, changes to already drawn elements can be made via the "Edit symbols" and "Replace symbols" command.

The application detects all the blocks present in the drawing, allowing the selection of new symbology, such as NEMA. 

Replacement can be performed on the entire multi-sheet or the whole project. Subsequently, it is advisable to perform a cross-reference operation to replace the registration crosses, pressing "Update".

Another innovation of SPAC Automazione 2024 concerns the data packages that will be published, when possible, already with the NEMA symbols included.