Choosing the right enclosure maybe as important as selecting the right product. An electronic enclosure, also known as housing, helps protect the circuit board allowing it to function properly. Elements (e.g. water, wind, dust, dirt, heat, cold, humidity, and chemicals) in the surrounding environment could damage or deteriorate the product.

For example, large temperature variations between the inside and outside of the enclosure can result in pressure differences that may create a vacuum and draw water through the fittings or component and gasket seals. Or when moist air reaches its dew point, it can no longer hold its form and forms moisture droplets being formed on any available surfaces. This is called condensation. When temperatures are below freezing, it will condense into frost. After time, corrosion occurs and causes electrical resistance, which in turn generates additional heat, product performance problems, rusting, increasing risk of circuit shorting out, and arcing and sparking incidences.

Here are six factors to think about before choosing an enclosure:

• Environment
• Application
• Thermal management requirements
• Enclosure performance standards
• Material
• Size

ENVIRONMENT
To determine which enclosure offers the best protection, think of the most important, potential environmental threat. Some questions to think about are:

• What are the environmental conditions?
• What is the primary environmental concern?
• What are the temperature and humidity extremes?

APPLICATION
Application can be associated with market or product. Market applications would be locations such as water treatment plants, parking garages, pools, arenas, repair shops, food plants, etc. Product applications would be physical enclosure requirements such as wall mount, duct mount, easy access, etc.

THERMAL MANAGEMENT REQUIREMENTS
To maximize the efficiency and lifecycle of products, it is important to be able to manage heat buildup. Whether it’s to dissipate or to add heat, effective thermal management is vital.

ENCLOSURE PERFORMANCE STANDARDS
It is important to understand the enclosure ratings and the level of protection they provide because a single enclosure does not protect against all the elements equally.

To standardize enclosure performance in North America, the National Electrical Manufacturers Association (NEMA), Underwriters Laboratories Inc. (UL), and Canadian Standards Association (CSA) are the commonly recognized standards organization. To standardize enclosure performance internationally, the International Electrotechnical Commission (IEC) prepares and publishes international standards for all electrical, electronic, and related technologies.

Table 1 describes the NEMA, UL, CSA, and IEC enclosure ratings for both non-hazardous and hazardous locations. For hazardous locations in North America, NEMA has categorized it further and separated it by class, division and groups as seen in Table 2. The class defines the general nature of hazardous material in the surrounding atmosphere, the division defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere, and the group defines the hazardous material in the surrounding atmosphere. The difference between NEMA and UL is that NEMA does not require a third party testing and leaves compliance completely up to the manufacturer.

Table 1: Enclosure Ratings for Non-Hazardous & Hazardous Areas

Table 2: NEMA Classes, Divisions & Groups for Hazardous Areas

Table 3: IEC Enclosure Ratings

MATERIAL
Deciding on the appropriate material for the enclosure, potential environmental threats and application location should be considered. Enclosures are constructed of metals (eg. aluminum, steel) or non-metallic materials (eg. plastic, fiberglass), depending on application performance requirements as seen in Table 4. Table 5 describes the advantages and disadvantages of each enclosure material.

Table 4: Application Performance & Enclosure Materials Application Performance Enclosure Materials

Table 5: Advantages & Disadvantages of Enclosure Materials

SIZE
When specifying, enclosure size needs to be considered. Some questions to think about are:

• Where will the equipment be mounted?
• Does your application have specific enclosure location requirements?

It is essential to look at all six determinates – environment, application, thermal management requirements, enclosure performance standards, material, and size – prior to choosing an enclosure. Understanding all six factors will help you make a better choice when it comes to choosing the correct enclosure for the job. In essence, it will promote safety, define minimum levels of product performance, and minimize future maintenance expenses.