Electrical enclosures: not just a box anymore

The ideal electrical enclosure should install and remove easily, protect valuable equipment, allow the housed components to be accessed easily, and resist environmental hazards. The key steps in determining the best enclosure include assessing the building's environment, the electrical equipment's protection and size requirements, and the accessibility needed for time- and cost-efficient mainte...

02/01/2008


The ideal electrical enclosure should install and remove easily, protect valuable equipment, allow the housed components to be accessed easily, and resist environmental hazards. The key steps in determining the best enclosure include assessing the building's environment, the electrical equipment's protection and size requirements, and the accessibility needed for time- and cost-efficient maintenance and service. By identifying the required demands, engineers can simply and accurately specify an optimal electrical enclosure to provide dependable protection and long operational life.

The most important step is to consider the enclosure's environment. First, in order to determine the resistance needed, evaluate the environmental contaminants that could potentially harm the electronics and/or enclosure, including dust, dirt, and other debris; water in washdown environments; and harsh chemicals and UV light. The temperature both inside and outside of the enclosure is a key environmental factor to consider as well. Plus, invisible hazards such as electromagnetic or radio frequency interference also can obstruct equipment operation, and busy industrial environments may result in accidental impact or shock, damaging improperly protected electrical components.

Because some components are more susceptible to damage than others, note whether the application involves sensitive electronics—requiring significant protection—or moreresistant electric switches and relays. Enclosures are developed in various materials, many of which effectively resist corrosion and protect equipment in harsh applications. Enclosures are available with keylocking and padlocking systems to deliver additional equipment security.

Electrical equipment must be protected while remaining accessible. Anticipating the frequency of maintenance will help determine which additional enclosure features your application requires. Removable panels, double-hinged doors, and data interface ports assist in streamlining equipment maintenance.

Additionally, enclosures are available in horizontal, low-profile, wall-mount, and several additional models to integrate seamlessly into a variety of floor plans while providing operators with improved ergonomics and equipment accessibility.

Periodic enclosure inspection ensures proper performance in the environment and protection against electric shock. Where applicable, check the gasket for compression set, the latching to make certain the door seals properly, and the door interlock to ensure the accessibility meets the requirements. Also check the enclosure for corrosion and make sure all the conductive parts are properly bonded. Replacement parts and accessories, such as touch-up paint, are available from most enclosure manufacturers to enhance product life.

Common enclosure requirements are found in the National Fire Protection Association (NFPA 70, also known as National Electric Code, NFPA 79) National Electrical Manufacturers Assn. (NEMA 250), Underwriters Laboratories (UL 50, UL 508A), Canadian Standards Assn. (CSA 22.2), and International Electrotechnical Commission (IEC 60529). North American practice is to match the environmental protection requirement to a specific enclosure Type rating.

The most common Type ratings are:

  • Type 1: Enclosures are intended for indoor use, primarily to provide a degree of protection against contact with the enclosed equipment or locations where unusual service conditions don't exist.

  • Type 3R: Enclosures are intended for outdoor use, primarily to provide a degree of protection against falling rain and sleet; they are undamaged by the formation of ice on the enclosure.

  • Type 4: Enclosures are intended for indoor or outdoor use, primarily to provide a degree of protection against windblown dust and rain, splashing water, and hose-directed water; they are undamaged by the formation of ice on the enclosure.

  • Type 4X: Enclosures are intended for indoor or outdoor use, primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, and hose-directed water; they are undamaged by the formation of ice on the enclosure.

  • Type 12: Enclosures are intended for indoor use, primarily to provide a degree of protection against dust, falling dirt, and dripping non-corrosive liquids.

Third party listing from UL/CSA ensures that the selected type rated enclosure is performance tested for ingress, bonding, and corrosion, and that it meets additional construction requirements for minimum metal thickness, latching, and coating finishing.

The size and mounting requirements of the application's electronics also are critical to determining a proper fit. Engineers should calculate the minimum height, width, and depth that the equipment requires, including wire bend space, and note any space and installation limitations in the application area.


Author Information

Glen Kampa is program manager with Hoffman, Anoka, Minn.




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