The design of enclosures to house networking servers and components should be guided by one overriding concern — heat. Servers, in particular, generate a great deal of heat, so an enclosure must be capable of dissipating that heat to ensure that the components deliver their expected life.

Aside from heat dissipation, enclosures for networking systems should provide for easy access to the interior, facilitate assembly and mounting, and provide for wiring management. Here are some practical guidelines for designing enclosures for networking equipment.

Exhaust fans should be mounted in the top of the cabinet to remove heat.
1. Beat the heat. The more servers used, the more heat generated. While networks consisting of just a few servers can be housed in standard cabinets and enclosures, systems with multiple or densely packed servers should be housed in special server racks. Such racks include perforations or ventilation slots on the front, sides, rear and top to promote maximum airflow around components.

To increase airflow, the enclosure should incorporate fans and blowers at strategic locations. Exhaust fans mounted at the top of the cabinet are most common and are very efficient in removing heat. However, if the cabinet is densely packed with servers and other equipment, the air flow path gets blocked and this creates back pressure inside the cabinet. Such back pressure will lower the performance (CFM capacity) of the fans. For such conditions, blowers should be used in addition to exhaust fans. Blowers are generally mounted at the bottom of the cabinet rack and blow cold ambient air into the cabinet. Fan tray assemblies can be mounted directly below critical components to direct airflow against local hot spots and to prevent hot air from being trapped within the enclosure.

2. Plan for the environment. Local conditions may dictate the use of specially designed racks and enclosures. For example, seismic racks should be specified for areas prone to earthquakes. These racks conform to Telcordia (formerly Bellcore) #GR-63-CORE, Issue 1, and feature reinforced construction to provide seismic protection.

In a factory, NEMA enclosures should be used to protect components from water and dust. NEMA cabinets have door seals to prevent water and dust entry. However, care must be taken to specify the correct NEMA designation. For example, many users specify NEMA 12 enclosures thinking they provide more environmental protection than NEMA 4. In fact, the opposite is true.

For office settings, open racks are often sufficient. These racks are typically located in a separate room, and do not need protection from water or dust. The open rack configuration provides maximum airflow around components and costs less than a fully enclosed cabinet rack.

3. Provide easy access. Despite all best efforts, components do occasionally fail. In addition, networks often must be reconfigured to provide more capacity. Thus, the enclosure should be designed for easy access to the interior by incorporating removable doors, side panels and backs

Enclosures should be designed for easy access to the interior.
4. Plan for assembly and mounting. The most time-consuming part of building a rack assembly is mounting the components. Some vendors ease this task and speed assembly by supplying equipment mounting rails with pre-tapped holes. In addition, some servers require special adapters and mounting rails, so care must be taken to ensure that the servers fit the racks being considered.

5. Plan cable management. Un or - ganized cables can significantly increase the time required to assemble equipment and make repairs. There fore, the enclosure should include cable management accessories. These parts not only simplify routing and repair, but also provide a neat, orderly appearance.

6. Ask about custom and pre-assembled enclosures. Most vendors offer these modifications at little or no extra cost. Pre-assembly at the factory can provide a more cost-effective solution than standard enclosures.

7. Ask about design support. Work with a vendor who will accept your drawings and recommend cost-saving alternatives. In addition, choose vendors that offer a broad range of enclosure types and sizes, and accessories, so you can more exactly match your needs.

mind when designing and specifying enclosures to house servers and other sensitive electronic components will not only extend the life of your equipment, it will also make it much simpler to maintain.

This article was written by Ravi Jain, Director of Engineering, Bud Industries Inc. (Willoughby, OH). For more information, contact Mr. Jain at This email address is being protected from spambots. You need JavaScript enabled to view it., or click here .

Embedded Technology Magazine

This article first appeared in the November, 2008 issue of Embedded Technology Magazine.

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