How To Avoid IT System Failures
Prevent equipment overheating in server rooms using ceiling-mount spot air conditioners.
April 1, 2013 by Eddie Stevenson
As businesses and organizations increase their reliance on IT equipment such as servers and telecom switches for their vital, everyday business functions, they face a new and serious challenge: finding a cost-effective way to keep the equipment cool.
IT equipment is usually housed in a dedicated server room, also referred to as a server closet, office data centre, computer room, telecom room, network closet, and so on. Even for small businesses, a server room can easily contain two or more racks of equipment that are heat-sensitive and a source of considerable heat themselves. This equipment must be kept cool in order to prevent it from malfunctioning or incurring expensive damage. More serious consequences can result when a heat-related IT equipment failure causes a business interruption.
A building’s central air-conditioning system can sometimes provide the necessary cooling, but it is usually expensive, as well as being a wasteful use of energy. This is especially true since most IT equipment must operate continuously, including periods when the building is unoccupied and does not otherwise require cooling.
Moreover, the temperature in the server room usually needs to be kept lower than the rest of the office space, and its higher heat-load requires more cooling power. Unless air conditioning can be delivered separately to the server room, other parts of the office can become uncomfortably cold for employees working there. In addition, during cool-weather months, if the central air conditioning system switches to heating mode, the server room and its equipment will be heated along with the rest of the building. When that happens, a heat-caused IT equipment disaster is almost inevitable. For these reasons, server rooms usually require their own dedicated air-conditioning system.
GROWTH IN THE USE OF SERVER ROOMS
Computers and associated electronics equipment have become essential to a wide range of business activities, including general operations, accounting, Internet transactions, internal and external e-mail, IP telephones, hotel pay-per-view and satellite television systems, etc. The dynamic growth in the amount of electronics equipment used by businesses to perform these functions means that dedicated server rooms are increasingly required to house this equipment, separate from general office space. Electronics equipment can suffer both short- and long-term effects from overheating.
In some situations, inadequately cooled equipment may continue to function and show no immediate signs of overheating, but its life cycle may be considerably shortened, adding to investment costs. In other situations, severe overheating and accompanying system failure can occur very quickly, especially if there are several or more racks of equipment, which can generate a large amount of heat.
If the temperature rises to a dangerous level, servers, which contain a company’s critical data, will usually shut themselves down to prevent possible damage or data loss. Network routers, which handle a company’s internal and external data transmissions, such as e-mail and telephone communications, however, are even more vulnerable. Overheating can permanently damage these, requiring costly replacement. Potentially even more costly than equipment replacement is system downtime, which will bring business activities and transactions supported by the electronics equipment to a halt.
A HISTORICAL PERSPECTIVE
Originally, mainframe computers, which produced very high amounts of heat, were housed in their own rooms the size of basketball courts. Huge air-conditioning systems kept the ambient temperature at a constant 55F. Later, with the introduction of server technology, sophisticated precision cooling systems were specifically designed to accommodate the many dozens or even hundreds of racks of equipment contained in large, dedicated data centres.
Today, the proliferation of server rooms within general-use office space presents new challenges for air conditioning. Until recently, providing server rooms with dedicated air conditioning has most commonly been accomplished with either mini-split or precision cooling systems. The introduction of a relatively new class of self-contained commercial air conditioners, called spot air conditioners or spot coolers, offers an alternative to those systems.
HOW THEY WORK
Conventional air conditioners, including precision cooling and mini-split systems, consist of two separate units, one containing a condenser and the other an evaporator coil. Self-contained spot air conditioners, as shown in Figure 1, combine both a condenser and an evaporator coil in a single unit. Cold refrigerant flows through copper tubing from the condenser to the evaporator coil. A fan blows over the coil, pushing cold air out. A second fan pushes hot exhaust air out through a flexible duct, which is usually directed into the crawl space above a drop ceiling.
In addition to air-cooled spot air conditioners, water-cooled models can be used in applications where there is no available space for the hot exhaust air. With air- or water-cooled units, excess moisture removed from the air collects in a small condensation tank and is automatically pumped out to a drain or, in the case of portable units, can also be disposed of manually.
PORTABLE VERSUS CEILING-MOUNT
Spot air conditioners are available in both portable as well as ceiling-mount models. Even though portable models are primarily designed for applications where they can be quickly and easily moved, they are often used in permanent installations as well.
An advantage of portable spot air conditioners is their small size. This makes them suited for use in applications where space is at a premium, such as small to medium-size server rooms. Many server rooms, however, do not have even the small amount of floor space that a portable spot air conditioner requires. In such cases, a ceiling-mount model is usually a practical choice (see Figure 2).
In addition to their low cost, ceiling-mount spot air conditioners are smaller than precision cooling systems, so they are easier to install in the limited crawl space found above most server rooms. Also, ceiling-mount spot air conditioners consist of only a single, precharged unit. Some ceiling-mount spot air conditioners are available in 115-V models.
In some crawl spaces, obstructions such as light fixtures can limit where an air conditioner can be placed. To overcome this, ceiling-mount spot air conditioners use flexible air ducts for both supply and return. Also, the location of the supply and return can be changed to eliminate any new hot spots that may result from changes in equipment configuration.
WHAT TO LOOK FOR
When choosing a ceiling-mount spot air conditioner, features can vary greatly. Here are some important things to look for:
High sensible cooling capacity: Heat-generating IT equipment requires a higher sensible cooling capacity than most applications, so before choosing an air conditioner it is essential to determine the minimum sensible cooling capacity needed. Also, be sure to take into account possible future increases in the amount of equipment to be cooled.
Quality of manufacturing: Look for a system with fan motors that are fully enclosed in protective housings to prevent dust from building up. Dust that accumulates on the motors can absorb moisture, leading to corrosion or electrical shorts. Sheet-metal panels should have stress-relief notches at the bends and should be attached to the frame at load-bearing points by machine screws, or by lighter-duty sheet-metal screws. Is the refrigeration unit hermetically sealed, or does it have service valves, which are prone to leaks? Are the refrigerant pipes connected by reducers and expanders or distributors, instead of by pinchi
ng and brazing? Pinching and brazing can restrict the flow of the refrigerant, reducing cooling efficiency and long-term performance. In addition, the connections created using this method are weaker and more subject to vibration-caused stress cracks and subsequent leakage.
Built-in features: The best self-contained air conditioners will usually come with built-in features that can have a major impact on the cost and ease of installation, as well as on the ease of use in daily operation. Some of the most important features include:
• Vibration isolators
• Mounting brackets that allow installation with off-the-shelf hardware
• Condensate pump
• Air supply and return flanges
• Wall-mounted, programmable controller
• Easy integration with an energy management system (EMS)
• Connection to building fire alarm, for automatic safety shutoff
• Connection to building control system, for remote control and monitoring of operation
• High seasonal energy efficiency ratio (SEER)
Established manufacturer: Look for a company that has established itself for many years in the industry and stands out as a leading manufacturer of air-conditioning equipment. This is a good sign that the company will be around to support their equipment well into the future.
Also look for a company with a broad distribution base and a large number of dealers who will support and service their equipment where you are located. Additionally, some manufacturers cover their equipment for both parts and labour for the entire length of the warranty. <>
Eddie Stevenson is CIS marketing supervisor with Denso Sales. Stevenson can be reached at firstname.lastname@example.org.