Thinking Inside the Box

Thinking Inside the Box – Industry Trend or Event

Eric Wentz

The importance of proper enclosure choice.

The world’s communications networks are adding traffic at an amazing alarming rate. Nowhere is this growth more apparent than in the wireless sector of the communications industry. Increased network demand requires more bandwidth, more agility and greater overall network reliability.

One of the results of this growth is the migration of significant network components from a traditional central office to outside plant installations. This increased investment in outside plant hardware must be well protected for the network business model to succeed.

Outside plant equipment “boxes” come in a variety of shapes, sizes and colors, and house an array of different network hardware components. These enclosures are often the sole means of containment and protection offered otherwise sensitive and fragile electronic-transmission equipment.

Ironically, enclosure selection is not always considered a critical or decisive element of the overall network. You should consider and discuss several key criteria before specifying a particular enclosure for deployment. These include enclosure technical design, durability and flexibility.

Enclosure Design

An enclosure’s ability to provide both protection and long service life is highly dependent on its technical design. Outside-plant-equipment enclosures should meet stringent safety and agency standards, including, UL/CSA, Nema, NRTL and, in some cases, Telcordia and NFPA standards. Certain regions also demand seismic considerations, requiring Zone 2 or Zone 4 certifications.

Each enclosure should be tailored specifically for the application. For example, if the enclosure houses powering electronics or other network hardware that produces heat as an operational byproduct, thermodynamics become critical. Appropriate air movement within the enclosure will not only become key to hardware reliability, but also a significant contributing factor to maximizing the equipment’s service life.

Thermal management is one of the most significant aspects of enclosure design. Temperature-related design criteria are even more critical when you need to contend with wide temperature variations. Such conditions can result from either large disparity between day and nighttime ambient temperatures or extreme seasonal fluctuations. Solar loading or extreme wind conditions can complicate thermodynamics. All design calculations must be verified by testing under full temperature and solar loading conditions. Because national standards don’t address these specific operational requirements, decision makers should require enclosure manufacturers to provide an operational certification or actual test results to ensure satisfactory performance in the field.

Enclosure designs that consider such temperature conditions and work to maximize convection cooling without fan-forced air displacement address this issue without creating new maintenance concerns. Fans may require both routine maintenance and filter replacement, while strategically placed cooling louvers can create natural-convection air movement without the associated maintenance concerns. Some applications will need to take advantage of both fans and ventilation openings to obtain acceptable inside temperature ranges.

Compartmentalization within the enclosure also can serve to isolate temperature-sensitive components from heat-generating electronics. Batteries used in backup-power systems, for example, are highly susceptible to temperature variations. The effects of temperature on battery life are well documented. For every 10[degrees] C (18[degrees] F) rise in ambient temperature, battery life is cut in half.

Many generic enclosure systems place batteries in less than ideal configurations, either near heat-producing equipment or in areas with limited convection cooling. As a result, service providers are faced with premature and costly battery replacements. Separation, as well as placing the batteries in either a top or bottom shelf area within the enclosure, can work to either warm or cool the batteries (depending on the climatic requirements of the region).

Additionally, enclosures must serve to protect sensitive — and costly — network hardware from dust, moisture and insects. Although seemingly inconsequential, such intrusions can cause serious hardware damage and can affect overall system reliability negatively.

As competition among communications service providers increases, the need for rapid deployment also has risen on the priority list. Enclosure design must enable a quick and efficient installation process, free from time-consuming complexities.

Enclosure Durability

Outside plant enclosures are subjected to the most demanding environmental conditions imaginable. They must endure wide temperature variations, prolonged exposure to an array of harsh weather conditions, and hold up against both manmade and natural disasters.

Material choice and fabrication techniques are of obvious importance. Leading OSP enclosures incorporate non-rusting, all-aluminum, IS0-controlled, welded construction and weather-resistant, powder-coated finishes. These elements allow enclosures the greatest advantage in maximizing service life of both the enclosures themselves and the network equipment they house.

The strategic significance of choosing a quality enclosure is less obvious. It’s becoming increasingly difficult and more costly to obtain enclosure-placement easements. Pole space is limited, and utility and private easements are both scarce and expensive. A long-life enclosure helps prevent difficulties, including possible easement forfeiture, when more frequent enclosure replacement or upgrading is required.

Maximizing the service life of the enclosure is both a fiscal and a strategic issue. The fiscal benefits of a quality enclosure are clear — a quality enclosure with a long service life helps maximize return on investment of both the enclosure and its contents.

Enclosure security also is a critical consideration. The cost of network hardware certainly warrants appropriate protection from potential vandals, thieves and intruders. The use of industry-standard lock and latch systems provides an appropriate level of security, while not inconveniencing or impeding access for maintenance personnel. In high-risk locations, additional security measures should be incorporated. Leading enclosure manufacturers offer optional security devices to increase the level of protection.

Enclosure Flexibility

Another important enclosure-selection criteria is its ability to meet both current and future network needs. Ideally, and for the easement-acquisition issues already mentioned, an enclosure should have the ability to grow with network requirements.

Scaleability is a critical factor when considering the addition of expanded communications services. Many network business models work only if scaleability will allow the system to grow incrementally as additional revenue-generating communications services are added. Replacing network hardware is much more capital-intensive than installing a platform that can grow incrementally as new services and subscriber bases increase.

For example, if a power installation requires additional capacity as a result of either expanded services or additional subscribers, adding to an existing enclosure is often a much more efficient means of expanding the system’s overall capacity than completely replacing the installation.

Leading enclosure manufacturers have recognized this need for incremental growth and have developed enclosure systems that add both capacity and application flexibility to their product offerings.

As easement space becomes scarce, mounting flexibility has taken on new importance. Having the option of either pole- or ground-mounting enclosures, while retaining common connections and equipment shelves, assists network personnel in both the installation and maintenance processes. The ability to co-locate network hardware in common enclosures or integrate installations in underground vaults also is sometimes required.

Maintenance personnel will need the enclosure to be service-friendly and accessible. Housed equipment and network connections should be reachable. This element becomes especially important in pole-mount or aerial applications where maintenance personnel are accessing the installation from bucket or ladder trucks.

Other important flexibility criteria include size, configuration and color choice. With increasing regulatory pressure from individual municipalities to limit the amount of visible-hardware intrusion, the ability to make network-hardware installations blend into their surroundings is important. Low-profile or small-footprint enclosures may allow service providers to make the most of smaller easements and limit the amount of hardware visibility.

Enclosure color choice, while a seemingly benign issue, can work miracles in helping otherwise obtrusive enclosures blend into their surroundings. Green enclosures in landscaped, treed environments blend much more readily into the background than a tan-colored enclosure better suited for an arid, southwest installation.

Although enclosure choice may not be the most exciting or compelling element of network technology deployment, appropriate selection is critical to both system reliability and longevity.

An enclosure’s value is only as good as its ability to protect its contents, and its technical design, durability and flexibility should be key criteria in the selection process.

Wentz is vice president of marketing and Cross is product manager at Alpha Technologies (www.alpha.com).

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