Waterproof Enclosures
Suitable waterproof enclosures come in many varieties. Metal or plastic may be used to create a watertight container for outdoor embedded equipment.
Of course, equipment needs power to work, and will likely need to connect to an antenna and Ethernet cable. Each time you pierce a watertight enclosure, you provide another potential place for water to seep in.
The National Electrical Manufacturers Association (NEMA) provides guidelines for protection of electrical equipment from rain, ice, dust, and other contaminants. An enclosure with a rating of NEMA 3 or better is suitable for outdoor use in a fair climate. A NEMA 4X or NEMA 6 provides excellent protection, even from hose driven water and ice. For fixtures that pierce the body of an enclosure (such as cable glands and bulkhead connectors), NEMA assigns an ingress protection (IP) rating. An ingress protection rating of IP66 or IP67 will protect these holes from very strong jets of water. A good outdoor enclosure should also provide UV protection to prevent breakdown of the seal from exposure to the sun, as well as to protect the equipment inside.
Of course, finding NEMA rated enclosures may be a challenge in your local area. Often, locally available parts can be repurposed for use as enclosures. Rugged plastic or metal sprinkler boxes, electrical conduit housings, or even plastic food containers can be used in a pinch. When piercing an enclosure, use quality gaskets or o-rings along with a cable gland to seal the opening. UV stabilized silicone compound or other sealant can be used for temporary installations, but remember that cables flex in the wind, and glued joints will eventually weaken and allow moisture to seep in.
You can greatly extend the life of a plastic enclosure by providing some protection from the sun. Mounting the box in the shade, either beneath existing equipment, solar panel, or thin sheet of metal specifically for this purpose, will add to the life span of the box as well as the equipment contained inside.
Before putting any piece of electronics in a sealed box, be sure that it has minimal heat dissipation requirements. If your motherboard requires a fan or large heat sink, remember that there will be no airflow, and your electronics will likely bake to death on the tower. Only use electronic components that are designed to be used in an embedded environment.
Enclosures are given a NEMA rating according to the types of applications the enclosure serves.
- NEMA 1
NEMA 1 industrial enclosures are typically used for protecting controls and terminations from objects and personnel. This style of enclosure, while offering a latching door, does not have a gasketed sealing surface. NEMA 1 enclosures are used in applications where sealing out dust, oil, and water is not required. Motor start/stop stations are often housed in NEMA 1 enclosures. - NEMA 3R
NEMA 3R electrical enclosures are typically used in outdoor applications for wiring and junction boxes. This style of weatherproof enclosure provides protection against falling rain, sleet, snow, and external ice formation. Indoors they protect against dripping water. This style of enclosure does not have a gasketed sealing surface. Some models have hasps for padlocking. - NEMA 4
NEMA 4 industrial enclosures are used in many applications where an occasional washdown occurs or where machine tool cutter coolant is used. They also serve well in applications where a pressurized stream of water will be used. NEMA 4 enclosures are gasketed and the door is clamped for maximum sealing. They have continuous hinges, mounting feet, and padlock hasps. NEMA 4 enclosures are available in sizes from small wall mounts to two-door floor mount models. - NEMA 4X
NEMA 4X enclosures are typically made of stainless steel or plastic. These NEMA enclosures are used in harsher environments than standard NEMA 4 units. Applications where corrosive materials and caustic cleaners are used necessitate the use of a NEMA 4X enclosure. Applications include food, such as meat/ poultry processing facilities, where total washdown with disinfectants occur repeatedly and petro-chemical facilities, including offshore petroleum sites. NEMA 4X is used when protection from the worst environments is required. NEMA 4X industrial enclosures are available in sizes from small wall mounts to two-door floor mount models. Hubbell Wiegmann metal NEMA 4X enclosures are made of 304 stainless steel. - NEMA 12
NEMA 12 enclosures are designed to prevent the ingress of dust, water, and oil. NEMA 12 enclosures are most often used for indoor applications of automation control and electronic drives systems. Some examples are packaging, material handling, non-corrosive process control, and manufacturing applications. Gasketed doors seal the enclosure’s contents from airborne contaminants and non-pressurized water and oil. These NEMA enclosures are available in sizes from small wall mounts to two-door floor mount models. - NEMA 4 & 12
Hubbell Wiegmann’s “412” enclosures combine the attributes of NEMA 4 and NEMA 12 in an attractive, clean line enclosure. This enclosure features reversible doors for left or right opening, concealed hinges, and rear mounting holes for a more attractive installation. Optional mounting feet are available for conventional wall mounting. Wiegmann’s 412 enclosures are available in wall mount models up to 60″ x 36″.
