Enclosure Selection Basics

Enclosure Basics

An electrical enclosure is a cabinet for electrical or electronic equipment to mount switches, knobs and displays and to prevent electrical shock to equipment users and protect the contents from the environment. Regulations may dictate the features and performance of enclosures for electrical equipment in hazardous areas, such as petrochemical plants or coal mines. Electronic packaging may place many demands on an enclosure for heat dissipation, radio frequency interference and electrostatic discharge protection, as well as functional, aesthetic and commercial constraints.

Electrical enclosures are usually made from rigid plastics, metals, particularly stainless steel, carbon steel, and aluminum. Enclosures for some purposes have partially punched openings (knockouts) which can be removed to accommodate cables, connectors, or conduits. Where they are small and primarily intended to conceal electrical junctions from sight, or protect them from tampering, they are also known as junction boxes, street cabinets or technically as serving area interface.

NEMA Ratings

NEMA - National Electrical Manufacturers Association uses a standard rating system that defines the types of environments in which an electrical enclosure can be used, and frequently signifies a fixed enclosure's ability to withstand certain environmental conditions. Examples of NEMA ratings and environments they can be used in:

• NEMA 1 & NEMA 12. Rated for indoor use that protects against solid objects, dust and dirt.
• NEMA 4 Can protect against solid objects and is also waterproof and rust resistant. Commonly used outdoors.
• NEMA 7 Explosion proof enclosure. Design to contain an explosion within the enclosure and not causing any external hazards. Designed to be used in Class 1 Div. 1 and Class 1 Div. 2 environments.

There are several other types of NEMA ratings that can help us to determine which enclosure is best suited for our particular application. Things to consider besides NEMA rating when choosing an enclosure:

• NEMA ratings are just one of the many things we should consider when selecting an enclosure - Size
• Take into consideration how many different components you have to put in the enclosure, and how much room each component will need.
• Keep in mind the back plate (which is what the components are mounted to, will take up and inch or two of the total depth the enclosure can offer.
• Heat - Make sure that all of the heat generated be all of the components can be dissipated by the enclosure you decide to select.
• External obstacles - Think about what obstacles are surrounding the enclosure and how that might affect wire coming out of the panel, or other externally mounted components, such as disconnects, HMI’s switches, push buttons, etc.
• Material Type - Determine which material will best suit your needs. Steel, Stainless Steel, and many different kinds of non-metallic options are available and are all suited for different types of applications
  

By taking time to educate ourselves about the many different functions that an electrical enclosure and can offer and asking ourselves a few simple questions, we can ensure we select the proper enclosure for our specific application.