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. The enclosure is the only part of the equipment which is seen by users. It may be designed not only for its utilitarian requirements, but also to be pleasing to the eye. 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, esthetic and commercial constraints.
In the United States, the National Electrical Manufacturers Association (NEMA) publishes NEMA enclosure type standards for the performance of various classes of electrical enclosures. The NEMA standards cover corrosion resistance, ability to protect from rain and submersion, etc.
For IEC member countries, standard IEC 60529 classifies the ingress protection rating (IP Codes) of enclosures.
Electrical enclosures are usually made from rigid plastics, or metals such as steel, stainless steel, or aluminum. Steel cabinets may be painted or galvanized. Mass-produced equipment will generally have a customized enclosure, but standardized enclosures are made for custom-built or small production runs of equipment. For plastic enclosures ABS is used for indoor applications not in harsh environments. Polycarbonate, glass-reinforced, and fiberglass boxes are used where stronger cabinets are required, and may additionally have a gasket to exclude dust and moisture.
Metal cabinets may meet the conductivity requirements for electrical safety bonding and shielding of enclosed equipment from electromagnetic interference. Non-metallic enclosures may require additional installation steps to ensure metallic conduit systems are properly bonded.
Stainless steel and carbon steel
Carbon steel and stainless steel are both used for enclosure construction due to their high durability and corrosion resistance. These materials are also moisture resistant and chemical resistant. They are the strongest of the construction options.
Stainless steel enclosures are suited for medical, pharma, and food industry applications since they are bacterial and fungal resistant due to their non-porous quality. Stainless steel enclosures may be specified to permit wash-down cleaning in, for example, food manufacturing areas.
Aluminum is chosen because of its light weight, relative strength, low cost, and corrosion resistance. It performs well in harsh environments and it is sturdy, capable of withstanding high impact with a high malleable strength. Aluminum also acts as a shield against electromagnetic interference.
Polycarbonate used for electrical enclosures is strong but light, non-conductive and non-magnetic. It is also resistant to corrosion and some acidic environments; however, it is sensitive to abrasive cleaners. Polycarbonate is the easiest material to modify.
Fiberglass enclosures resist chemicals in corrosive applications. The material can be used over all indoor and outdoor temperature ranges. Fiberglass can be installed in environments that are constantly wet.
F.A.Q about Cabinet
What is a 19-inch Rack Cabinet?
A 19-inch rack cabinet is a standardized size frame or enclosure for mounting equipment. Each piece of equipment has a front panel that is 19 inches wide. To determine if your rack cabinet is a 19тА│ rack, measure the hole to hole spacing and it will measure 18.31 inches.
What are the types of rack cabinets available?
The most common types are:
- Rack cabinets or Server Racks
- Open Frame racks - 4post racks
- Relay racks - 2Post racks
- Portable rack cabinets
- Wall Mount enclosures
What is a Rack Unit (U or RU)?
The Rack Unit is a unit of measurement used for defining the vertical space available in an equipment rack cabinet. A 'U' equals 1.75 inches or4.45cm. Rack-mountable equipment is usually designed to occupy an integer number of U. This dimension has been standardized by the Electronic Industries Alliance (EIA).
What are some common or standard heights for rack cabinets?
Server racks come in a wide variety of heights anywhere from 1U to 50U and above.
When are Four- post racks used?
Four-post racks allow for mounting rails to support equipment at the front and rear. These racks may be open in construction or enclosed by front and/or rear doors, side panels, or tops. Four-post racks can provide both robust support and security.
When are Two- post racks used?
Two-post racks provide just two vertical posts. Equipment can be mounted either via its front panel holes, or close to its center of gravity, depending on the design of the rack. Two-post racks are most often used for telecommunication installations.
What are the Applicable Standards for rack cabinets/enclosures design and manufacturing?
- The EIA-310. It is standardizing features like the Rack Unit, vertical & horizontal hole spacing, rack cabinet openings and front panel width.
- IEC Standards. IEC 60297 (IEC 60297-3-100, -101, -102, -104, -105 and IEC 60297-5) standardize the dimensions and the mechanical structure of the 19 inch rack cabinets.
What is the significance of the Rack Cabinet Depth?
Rack cabinet depth is important not only because it has to allow room for the depth of the particular equipment to be rack-mounted (deep servers vs. routers or switches), but also it has to allow sufficient room for cables as well as airflow indispensable in cooling rack cabinets and enclosures.
What rack cabinet options for front and rear doors are available?
Front as well as Rear doors are available in many different materials, sizes and with various ventilation options. Locking systems are also available on most doors. Choosing a ventilated front and rear door is key in air circulation by creating a front to back flow pattern within the rack cabinet.
What Side Panel options are available for rack cabinets and enclosures?
The typical types of rack cabinet side panels are: solid removable, solid fixed and louvered removable and fixed.
What is the most economical rack cabinet cooling technique?
Our approach to efficient cooling of datacenter rack cabinets begins with a sealed separation between the cold isle in front of the equipment row and the hot isle in the back of the equipment. The sealing between hot and cold is done at the front rail level of the enclosure. We implemented this solution, for instance, for a wide variety of Cisco routers: 2821, 7613, 3560E, 3845, 2911, 6509E, 4507R, 4510R, 4510E, 4900M.
Since the router is designed to intake cold air from the side, which is now left by our separation in the hot isle, we needed to create a duct that would connect the router's intake to the cold isle in front of the cabinet. We accomplished the whole task by designing a cold air intake plenum mounted under the router, and connecting this plenum through a duct to the intake on the side of the router.