The type of enclosure that you select for a project depends on where and how it will be used. Will the enclosure be used indoors or outdoors? Will it need to be waterproof? (Many indoor enclosures have this requirement.) Do you need to house networking and communications equipment? In that case, you need a cabinet or rack. Will your enclosure be used as a junction box? Will it accommodate DIN rails, or will it need to be DIN rail mountable itself? This article will help you answer these questions, guiding you to the right type of electronic enclosure, and offering selection considerations.
Computers started as an indoor phenomenon, but as chips grew smaller and more powerful, and as wireless connectivity evolved, computing power moved outdoors as well. Now, applications like traffic regulation, security cameras, and automated sprinklers need control electronics and wireless communications components to be housed close to where they are used. This is driving an increase in the use of weatherproof electrical enclosures.
While outdoor electronic enclosures are nothing new, the finer points may be new to some design engineers, who can easily make mistakes during the enclosure selection process. For helpful tips, see our blog post, Five Typical Mistakes in Specifying and Outdoor Enclosure.“
To understand what requirements are needed for your outdoor enclosure, you must think about the environmental threats imposed on your design.
Water. Electronic devices and PCB traces must be kept dry to prevent unintended paths for power and signal lines. Water causes corrosion, leading to premature failure. In most cases, water comes from rain, which may not always fall straight down, but may be driven by the wind at angles. During a downpour, an enclosure may be enveloped in water.
Wet conditions will affect the enclosure, too. Outdoor plastic enclosures, along with aluminum and fiberglass, are the most popular for outside settings because they are naturally corrosion resistant. Stainless steel is a suitable (but very costly) material for outdoor use. Powder-coated sheet metal is another possibility, but be aware that steel may rust if improper coatings are used.
Wind. While not as conductive as water, wind blown dust too can cause shorts between circuits. A coating of dust on devices can also provide unwelcome insulation, limiting heat dissipation and eventually leading to premature failure.
Heat. When the mercury rises, so too will the temperature rise on your outdoor designs. Heat dissipation should be a consideration. Metal enclosures have the ability to transfer heat away from components. Keep in mind that metal enclosures can also conduct heat into enclosures, especially if they are located in the sun.
Sun. Ultraviolet light degrades plastic, causing it to crack, discolor, and disintegrate. The light causes a chemical reaction that breaks the polymer chains. Special additives are added to plastic to make it resistant to the effects of the sun. UV-rated plastic is more expensive, up to twice the cost of regular plastic, so not all plastic enclosures have this protection.
Moisture. Carried in the air, moisture can eventually cause corrosion of delicate electronic devices. Eventually, moisture can cause components to fail prematurely.
Air pressure. Changes in air pressure can cause a gasket to fail, exposing internal components to moisture, water, and wind.
Selecting electrical enclosures for an indoor application is not as critical as selecting an enclosure for an outdoor application exposed to weather. On the other hand, the designer faces a bewildering array of enclosure options. Consider the needs of your application and start narrowing down your options by material and type.
Remember that, just because your application is indoors, it does not mean that the ingress of dust and moisture is not a concern. In manufacturing settings, there may be factory-floor washdown, airborne metal filings, corrosive vapors, and splashing coolant. Even in a clean indoor environment, your design needs basic protection from spilled coffee and dust.
Material
Box style enclosures are available in molded plastic, fiberglass, sheet metal steel, sheet metal aluminum, extruded aluminum, die-cast aluminum, and stainless steel. Racks and cabinets are always usually made of steel but are sometimes made of aluminum to reduce weight
Cost. Cost is always the first engineering consideration. When manufactured in quantity, molded plastic enclosures are the most cost effective. Simple sheet metal enclosures are affordable even in low quantities. Die cast aluminum is an excellent choice for the cost. Fiberglass is more expensive, although now there are available plastic enclosures with 10% fiberglass that have added strength at minimal extra cost. Stainless steel is extremely expensive. Naturally, standard off-the-shelf enclosures are far less costly than a custom enclosure. A custom enclosure is a great option when a standard enclosure will not work for your application.
Performance. Metal enclosures are best for transferring heat away from electronic components, and they offer EMI shielding. Molded plastic and fiberglass enclosures are corrosion resistant, as are die-cast enclosures and stainless-steel enclosures. Molded and die-cast boxes make cost-effective NEMA and IP-rated enclosures, compared to sheet metal boxes. Metal boxes can be powder-coated to add corrosion protection. In addition, special-purpose enclosures are available. For example, some enclosures offer optional infrared panels for communication, while others are designed specifically for use as fiber optic or electrical junction boxes.
Appearance. Molded plastic provides a polished look for designs that have frequent user interaction, such as a consumer good or medical device. If the enclosure will be used to house controls for a machine in a factory, then you can get away with the less sophisticated look of die-cast aluminum or sheet metal. Many extruded aluminum enclosures have attractive, colorful finishes and plastic end caps.
There is a lot to consider, so check out our article devoted to this topic, ”Choosing the Right Material for Your NEMA Enclosure.”
Type
There are many types of enclosures, ranging from large cabinet racks to tiny plastic boxes. Here are some things to think about.
How will the enclosure be used? If it will be portable or hand-held, then choose plastic for its light weight. Fiberglass is lighter than steel, so for large enclosures, fiberglass will be easier to ship and install.
Will it be exposed to impact, such as from forklifts? Then choose a die-cast aluminum, steel, or fiberglass-reinforced enclosure. Bud’s PTQ Series of fiberglass reinforced plastic enclosures are surprisingly strong, as shown in this video of a car driving over an enclosure.
Will it house indicators or displays? Plastic enclosures are available with clear plastic covers.
Will it include components of different types? Bud offers a dual compartment enclosure that is ideal for power components on one side and indicators on the other side. Also, our DPS and DPH Series of plastic boxes accept internal mounting panels in the cover, base, and body, giving the designer great flexibility in the location of internal components. These designs allow power components can be located far from signal electronics.
What is the weight of the components? Power supplies and heat sinks may need to be mounted on internal metal or plastic panels, which are available on some enclosures.
Will it need in-the-field maintenance? Hinged covers with latches make it easy for technicians to access internal components quickly.
How will your components be mounted? Bud offers enclosures made for internal DIN rail mounting. As well, some Bud electronic enclosures are able to be din rail mounted themselves.
How many circuit boards does your design have? Extruded aluminum enclosures often have an integrated card guide for holding a circuit board as do many die-cast enclosures. Bud also offers a multiboard terminal box that holds multiple small PCBs. Larger enclosures have internal mounting bosses.
Does your design need security? Cabinets are available with locking doors. Some box-style enclosures have hasps for padlocks.
What defines weatherproof electronic enclosures? The key factor is the seal between the cover and the body of the enclosure. The gasket should be continuous, made of an environmentally durable material that remains pliable in a wide temperature range, and is secured by a tight-fitting cover that is screwed down or tightly latched.
How to select a waterproof enclosure for electronics
The degree of protection is rated based on standards defined by the NEMA in North America and the IEC in Europe. Most designers know they need a NEMA-rated or IP-rated waterproof box for electronics, but they may not know which level of protection they need. A NEMA 4X enclosure goes beyond drip protection to defend against hose-directed water and windblown dust. The X signifies that the enclosure will not corrode. NEMA 4X is the minimum level of protection for an outdoor location. If your product will be used in a marine location, or even if you just want to be extra safe, then go with NEMA 6P, which protects internal components even when the enclosure is submerged for a short period of time.
Similar standards for Europe include IP66, which seals out wind and rain. IP67 adds protection against temporary submersion, and IP68 protects against submersion for an hour, often at little additional cost. IP54 rated enclosures should not be considered waterproof, as they protect against falling drips but not against a storm or factory washdown.
To preserve the waterproof rating, all cables going to the electronic enclosure must be sealed using cable glands. Similar seals must be provided around switches, indicators, and displays. A good option is a plastic enclosure with a transparent polycarbonate lid, so indicators can be read without creating the need to drill holes in the box which must then be properly sealed. When mounting an enclosure, be sure to look for options such as molded in brackets or externally attached mounting brackets to avoid having to seal all holes for mounting purposes.
Air pressure and heat can be managed with vents. The challenge, of course, is that the vent makes an opening in the enclosure. Breathable IP-rated vents have a waterproof vent membrane that allows air to pass but blocks moisture and dust. Some vents are even submersible. See our blog post, “Bud Industries Introduces IP67 Rated Vents.”
A network cabinet is an enclosed metal frame designed to house data and communications equipment such as servers, routers, switches, and data storage devices. There are different names for these cabinet racks depending on the application of the equipment they contain: networking, communications, servers, etc. If you hear a cabinet rack referred to as a communications cabinet or server rack, understand that the terms are interchangeable. Equipment racks are also used to house test equipment, factory controls, and scientific instruments.
Equipment suppliers design their products for mounting to a standard 19-inch rack via mounting flanges that are also known as mounting rails having standardized spacing that matches screw holes in the rack’s mounting rails. Other equipment can simply sit on a shelf within the rack or be installed inside a chassis mounted to the rack.
Network cabinets enable technicians to install equipment vertically, which conserves floor space and provides an organized layout. Sometimes cabinet racks are bolted to the floor, and sometimes they sit on casters. Wall-mount network cabinets free up floor space.
To keep equipment secure, protected from dust, and to avoid accidental contact, sides and cabinet doors are added around the frame to provide a protective enclosure. High ambient operating temperatures can shorten the life of electronic components, so fans are usually added to cabinets to maintain cooling airflow. Ventilation (such as louvers) may be incorporated into the cabinet sides, doors, tops and shelves.
Open racks (those without sides or doors) aren’t enclosed, but people call them enclosures anyway, and the same manufacturer that makes cabinet rack enclosures also makes open racks. Some users only need two point mounting so they use a relay rack which only has the mounting rails but no other sides.
Selection considerations include:
Load. Know the weight of your equipment, and make sure your cabinet’s load specification is up to the job.
Height. Many cabinets are ordered by height. The industry decided long ago that a standard unit for vertical space should be 1.75 inches, and equipment suppliers still describe their equipment as 1U, 2U, etc. If you know how many units you need, it’s easy to order the cabinet; enclosure suppliers state the number of U for each model. Note that the “u” dimension refers to the amount of space that is available for mounting equipment and excludes the top and base which is why overall height is often given as well.
Doors. Do you need a locking door? Clear plastic doors and glass doors let technicians view indicators. Steel doors allow for more privacy and security
Accessories. Shelves, fan trays, cable organizers, drawers, and other accessories turn a basic structure into a useable cabinet. Some cabinet racks, like our BudRack Professional Series, include accessories for a turn-key solution.
For more selection tips, see our blog post, “Five Tips for Selecting a Network Cabinet.”
A junction box is used to enclose electrical connections, such as the wires bringing electricity to machines, lighting, IT equipment, video cameras, and many other devices. The box provides protection in both directions: it keeps the connections safe from tampering, dust, and water, and it keeps people safe from unintentional contact with electricity. Electrical needs change over time, and a junction box provides an access point to the electrical system. In situations where maintenance is frequent, a hinged junction box enables convenient access.
For outdoor locations or for indoor factory washdown locations, use a NEMA junction box that is sealed against the elements. Typically, these are made of plastic for their corrosion resistance. A good example is Bud’s PN-A Series enclosures, which come in a wide range of sizes. For added strength, fiberglass junction boxes are available, such as Bud’s PIP Series boxes and PTQ Series enclosures.
For indoor locations, a metal junction box is the traditional solution. The steel construction provides a sturdy platform for connections and a long service life. Often these enclosures are referred to as NEMA 1 junction boxes, because electrical codes call for a box that will protect against the intrusion of fingers (NEMA 1 rating). Often such boxes include optional knockouts.
A terminal junction box also houses electrical connections, but the wires used are signal wires rather than electrical power wires. For machine controls and automation, input and output signal wires connect to electronics via terminal blocks having screw terminals. A good example is our PTT Series Terminal Junction Box.
Bud also offers an ATEX-rated box that can be used as an explosion-proof junction box in explosive atmosphere environments.
A DIN rail enclosure is an enclosure to which one or more DIN rails may be mounted. A DIN rail is a flat metal bar of standardized dimensions that provides a convenient means of mounting components to a wall or inside an enclosure. Installers simply snap or slide components into place on the rail. This is a popular format in control applications because the components tend to be modular and can be easily changed: power supplies, solenoids, actuators, circuit breakers, and terminal blocks. Manufacturers know this and design their products with DIN rail brackets.
Bud offers to these manufacturers several electronic enclosures designed to mount on DIN rails, such as our extruded aluminum DMX Series enclosure and our plastic DIN Rail Mount Multi-Board Box that accommodates up to three PCBs. Add your own printed circuit boards and your design is ready for DIN rail mounting. Our video shows a box attached to a DIN rail.
Bud also offers cabinets and enclosures capable of housing DIN-rail mounted components. Most of our large NEMA/IP-rated boxes have mounting bosses in the base to which DIN rails may be mounted. These DIN rail boxes are ideal for factory floor locations subject to washdown. A good example is our NBG Series of large plastic enclosures that, unlike metal cabinets, will not block the RF signals used in IoT applications.
This article has covered some of the main areas of application and types of enclosures. If your application requires a special solution, one that an off-the-shelf enclosure cannot satisfy, then visit our web page on custom electrical enclosures.
