energy savings

Data Center HVAC Design Considerations

Data Center #HVACData centers today not only require protection from the elements, but also need to be designed to save energy as it is estimated they consume about 1.5 percent of all total demand. According to the Natural Resources Defense Council, data centers are one of the largest and fastest growing consumers of electricity in the United States. In the U.S in 2013 three million computer rooms used enough electricity to match the annual output of 34 large coal-fired power plants. Annual consumption is projected to increase by roughly 47 billion kilowatt-hours by 2020. The NRDC recommends that best-practice efficiency behaviours across the data center industry need to be adopted as demand rises to unprecedented levels.

Energy Savings in Data Centers through HVAC Equipment

Traditionally when a building needs cooling, compressors engage and fans start to move air over cooling coils. This cooled air is used to condition the internal environment where the temperature is required to be lowered. This process is extremely effective but requires costly compressor and fan energy, adding avoidable cost considering external building temperature is lower than the temperature inside. When the outdoor enthalpy (a combination of temperature and humidity) is preferred over the indoor enthalpy, conditions are suitable for “free cooling”.  Depending on the geographic location of the facility, economizer cooling can represents a dramatic reduction in overall energy consumption.

Economizer Data CenterWhat is an Economizer and how can it reduce energy usage?

An economizer is like a window that automatically opens itself – with the added advantage of going through the rooftop AC’s filtration system. An airside economizer simply recognizes the preferred enthalpy of the outside air. When enthalpy conditions are suitable for “free cooling”, the economizer controls position outdoor air, return air, and relief dampers to facilitate free cooling through the first and sometimes second stages of cooling.

Economizers can contribute to a reduction in data center power consumption by utilizing the cooler external building temperatures to assist in cooling the facility and equipment when required. In maximizing energy savings and reducing HVAC cooling load, the cooling system’s product life can be extended.

A study on building control systems by Battelle Laboratories found that, on average, the normalized heating and cooling Energy Use Intensity (EUI) of buildings with economizers was 13 percent lower than those without economizers. When an airside economizer works properly, the savings are significant. Whether your company is looking to burnish its environmental credentials, to lower the cost of operating its data center, or both, a properly designed system integrating an airside economizer is a cornerstone of achieving both goals.

Economizers and Indoor Air Quality (IAQ)

A confined, un-aerated indoor space within a building allows gaseous fumes, odors, germs, and even fungi to grow in concentration to the point that the indoor air is qualitatively different from the ambient air. IAQ is important because the health and the comfort of people working indoors are an important factor in sustainable productivity. Poor IAQ in a working environment can cause discomfort or health problems sometimes resulting in a loss of productivity, increased errors, and even litigation. With the added benefit of reducing cost in power consumption, introducing outside air into a building via economizers can also contribute to improving indoor air quality. Following the relevant ASHRAE standards that apply to ventilation, air movement and exhausting of contaminants ensures that IAQ requirements will be met. To meet the requirements of ASHRAE 62 the outside air entering a building should be measured and controlled.

The most important part of an airside economizer are the damper blades that allow the control and supply of a fixed amount of outside air into the building. Parallel bladed economizers do a better job of mixing the outside and return air to provide optimal benefit to the system.  The sealing ability of the damper is essential to the system as a whole, when contending with extreme temperatures external to the building. AMCA certified dampers can ensure leakage rates meet the appropriate standards.

It has to be recognized that during different seasons and in different climates the benefits from economizers may vary.

Relevant Codes and Standards applicable to Data Center HVAC

Ruskin EconomizerFeaturing Ruskin’s exclusive one-piece galvanized airfoil blade and stainless steel jamb, the Economizers provide low-leakage performance as described in ASHRAE Standard 90.1.  Each unit also features Ruskin’s “SUREFLOW” sensing tubes and blade position indicator to help determine minimum airflow.  This also helps assist in mixed air temperature verses blade position field adjustments.

Data Center Protection

The Natural Resources Defense Council states that Data centers can be regarded as the back bone of a modern economy serving businesses and communications. Defending data means not only protecting it from Mother Nature but also giving back to her with sustainable designs. A question that must be considered during the design of a data center, is ‘How likely could the facility be compromised in extreme weather conditions such as tornadoes and hurricanes?’

When evaluating potential HVAC equipment it is advisable to use FEMA rated louvers and grilles. FEMA rated grilles and hurricane-resistant louvers have been tested against high windloads and large missile impacts. Outside air control dampers can seal up the center when necessary to reduce humidity and heat.

XP500 FEMA GRILLERuskin’s XP500S Extreme Weather Grille protects wall penetrations from flying debris caused by tornadoes, hurricanes, and severe storms.  This type of protection is critical in the design of Community Shelters (ICC-500) and Safe Rooms (FEMA 361). It offers designers a ventilation solution for their near-absolute life safety requirements. The heavy duty grille can be mounted internally, externally, or in conjunction with other louvers providing protection and certified performance. Rated for an industry leading 266 psf windload, the XP500S Grille meets or exceeds the building envelope protection requirements while complementing the construction of data centers.

Relevant Certification

  • FEMA P-361, Safe Rooms for Tornadoes and Hurricanes
  • ICC-500 – ICC/NSSA Standard for the Design and Construction of Storm Shelters

For more information about Ruskin’s complete product line, application and design support, and our state-of-the-art manufacturing capabilities, contact your local Ruskin representative nearest you or Contact Ruskin directly at (816) 761-7476.

Spiral Duct – The Energy Efficient Way to Go!

With energy costs going through the roof and no relief in sight, HVAC system designers and specifiers are taking a much harder look at the many choices in ductwork available to them today. One question that is being asked more and more is whether to choose rectangular or spiral duct for an HVAC system. If the healthy state of the spiral duct manufacturing industry is any indication, the trend in the United States is moving towards spiral duct, as specifiers become more enlightened to the advantages of circular duct.

The inherent energy- and labor-savings features of the duct’s design are what are causing this shift. This changeover has already happened in Western Europe, where the cost of energy has always been higher than that in the U.S. In the region of Scandinavia, for example, the percentage of the spiral duct market share has gone from 5 percent 40 years ago to 85 percent currently.

Some of this changeover resulted from specialist manufacturers intensifying their level of automation, standardization, and R&D, but the bottom line has been that growth was spurred along by the competitive edge created by spiral duct.

The design, installation, and performance benefits of spiral duct are many, with some appealing to HVAC contractors and others to HVAC system designers. Since energy efficiency is the biggest advantage.

AIRTIGHTNESS = ENERGY EFFICIENCY
Quality spiral duct, which includes round, oval, and flat oval configurations, exhibit a very high level of air tightness. Many leading manufacturers of sheet metal spiral duct can guarantee a line of spiral duct that meets or exceeds the highest air leakage standard, Class 3, recognized by the Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA). Since some duct is manufactured with self-sealing double-gaskets, the connection is guaranteed to prevent duct leakage.

Duct air leaks can waste energy and cause IAQ problems, such as condensation. Loose-fitting joints or blow outs of improperly maintained seams can cause problems in supply ductwork, while air leakage can allow soil gases and molds in crawl spaces and below slabs to enter return ductwork. When leakage is virtually eliminated, the cost for filtering, heating, cooling, and distributing the air is kept to a minimum. In addition, studies have shown that round duct has a lower airflow resistance, which significantly contributes to the energy efficiency of the system.

One industry study demonstrated that a shift in the U.S. to more airtight systems would mean an annual energy savings of approximately 10 TWh (terawatt hours, each equivalent to one billion kilowatt hours), which is comparable to the annual energy product of three nuclear power plants.

So that the correct flow of heated or cooled air can reach the areas to be conditioned, fans must transport the total airflow. A poorly designed or leaking duct system needs larger, and often more expensive fans to achieve the desired effect, as well as more space in the building’s design, where extra space is often at a premium.

With the many flow measurement units specially designed for circular duct that are now available, HVAC engineers also find that it is easier to measure the airflow passing through circular ductwork. With these relatively inexpensive devices, the ventilations systems can include fixed measuring units as a low-cost method of enabling regular check ups or continuous monitoring.

Another benefit of spiral duct that contributes to the overall IAQ of buildings with spiral ductwork is the ease of duct cleaning, using industry-recognized duct cleaning equipment outlined in the North American Insulation Manufacturers Association (NAIMA) Duct Cleaning Guide.

Aesthetics plays a very important role today as mechanical engineers, architects, and other decision makers are specifying ductwork. Innovative design elements often include exposed ductwork, to give a property a contemporary look. Spiral duct with gasketed joints requires no unsightly sealant at the connections, which enhances the clean look of the ductwork. Contributing to the attractive look of the duct is the fact that this type of duct requires fewer joints and flange connections, and requires less supports and hangers. In addition, the tight, gasketed seal allows the system to remain free of dirt streaking, common with manually sealed systems, ensuring that it will look good for many years. And those systems with RGS-3 registers do not require register taps, since they are mounted directly to the ductwork, again giving it a progressive, streamlined appearance.

Finally – of concern to the HVAC system designer – is the fact that round duct that includes a double wall system with a non-woven poly fabric liner can deliver a level of acoustical performance competitive with other types of ducts.

CONTRACTOR FRIENDLY
How do the HVAC contractors who install ductwork view the choice of spiral ductwork? The overall cost of spiral ductwork can be relatively low because installation moves more quickly than with other forms of duct. Correct fit at each joint can be counted on with premium spiral duct because standardized components are manufactured to tolerances of -0.25 percent. And elimination of sealants speeds installation along, as well.

Likewise, the lighter weight of spiral ductwork enables one worker to install some sections of round duct into place, rather than two, which also adds to labor savings. Manufacturers say that the complete weight for a typical system comprising a normal combination of straight ducts, bends, and diffusers, can typically be 30 to 40 percent lower for a circular system.

Other advantages to the contractor are the ability of circular duct to be nested, with various sizes resting together, which helps with storage and transportation, and the duct’s inherent strength, created by the strong seams made during the fabrication process, which gives each section an increased rigidity. This also reduces the need for additional stiffeners and hangers during installation.

Specifying the best duct system for each project requires a careful study of the many choices of duct products and their inherent benefits. With energy costs on the mind of everyone much more in recent years, it always pays to study and compare ductwork design before selecting the best type to be used for a specific application.