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.

Ventilation in Health Care Facilities #IAQ

Ventilation in Medical FacilitiesOutside air management is extremely critical in health care facilities. Today’s HVAC system designer has many choices when it comes to managing outside air. However, reviewing the requirements identified in the building codes permits the designer to focus on the control strategies that are compliant. With this knowledge, the HVAC designer can eliminate several alternatives and choose among the appropriate strategies.

ASHRAE, the American Institute of Architects (AIA), and the International Building Code (IBC) provide designers with the necessary IAQ standards and goals that will permit “acceptable indoor air quality,” but they are not intended to necessarily describe how to devise a ventilation system that applies these instructions to actual applications.

The Centers for Disease Control (CDC) recommends that ventilation systems be monitored to ensure proper ventilation, early detection of operational problems, optimized performance for particulate removal, and elimination of excess moisture. The CDC also advises that AIA and ASHRAE guidelines be used as minimum standards where state or local regulations are not in place for health care facilities.

IBC identifies requirements for ventilation that apply to all building types. Therefore, it is important that the system designer consult the ASHRAE Handbook—HVAC Applications, the AIA Guidelines for Design and Construction of Hospital and Health Care Facilities, as well as the IBC (or local building and mechanical codes). The Handbook further states that where higher outside air requirements are called for, they should be used.

Pressure Seal DampersIn addition to providing a controlled ventilation system that regulates and maintains a constant supply of design ventilation air, the HVAC designer must be cognizant of energy codes as well. A leakage criterion exists for dampers that are integral to the building envelope. More than half of the states have adopted the International Energy Conservation Code (IECC), referenced by the IBC. The IECC states that dampers integral to the building envelope “shall be equipped with motorized dampers with a maximum leakage of 3 cfm/ft² at 1.0 in. w.g. when tested in accordance with AMCA 500.” This requirement is only important for health care environments that are not occupied 24/7 (day care facilities, administration offices, doctor offices, etc.), as well as areas that utilize and require emergency lock-down systems.

Critical Air Paths

Ruskin PSD Pressure Seal Dampers are ideal for buildings with critical air paths including food facilities, federal buildings, pharmaceutical facilities, laboratories, hospitals, biotech labs, nuclear facilities, chemical process plants and military installations.

RSKN_Go_Green_LogoFor 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.

High Performance Air Systems – HPAS

spiral duct High performance ducted air systems (HPAS) use the best of what ducted systems can offer, and compared to VRF, provide better comfort, meet ventilation codes, have a lower initial cost, consume less energy, carry no refrigerant risk, require less maintenance and performance is certified by AMCA, AHRI.

HPAS consists of advanced digital controls, low-leak economizers for free-cooling, spiral/oval static-regain ducting, variable air volume technology, well-placed diffusers,  high efficiency fans,  superior filtration systems, air-to-air energy recovery, and variable flow compressors.

air control damperComfort, flexibility, and efficiency remain the key objectives of office HVAC.  With high performance air systems it begins with multiple zones using temperature control which can be as small as one individual office. VRF zone size is limited by the necessity for rooms large enough to disperse the refrigerant charge of the entire system per ANSI/ASHRAE Stds. 15 and 34 and local codes.

High performance air system offers better filtration with the option for MERV-13 or better filters, or photocatalytic air cleaning compared to the residential type filters found in VRF systems. Noise can also be an issue with non-ducted systems because of the small fans in the room or above the ceiling. Regarding ventilation, ASHRAE 62 ventilation codes must be met at all times during occupied hours.  VRF systems must use a separate ducted system to provide ventilation air to each and every zone.  This coupled with the need to run refrigerant lines throughout the building drive up the first cost significantly beyond a HPAS.

From a flexibility standpoint, it is easier to move diffusers and duct take-off branches, vs. DX fan coils and refrigerant lines.

What about cost?  Typical installed costs* for various systems are summarized here 

VRF $20 to $26/sq.ft.
Chilled beam $30 to $45/sq.ft
VAV Rooftop/ High Performance Air System $15 to $20/sq.ft.
Chiller and High Performance Air system $17 to $24/sq.

spiral ductSeveral energy-reducing features distinguish high performance air systems from basic ducted systems. For lower fan energy consumption, system designers achieve the best airflow performance by selecting the fan with the lowest power (not always the lowest cost, or the smallest fan).  All AHU (air handler unit), rooftop, and fan manufacturer’s selection programs provide a variety of fan selections to meet the airflow and system pressure requirements  Further optimization comes by avoiding oversizing design loads, lowering design supply air temperature, and specifying low leak spiral/oval ducting.  Next is design of a lower pressure drop air systems using large coils, large filter banks, static-regain duct design, and aerodynamic ducts (large radius elbows and fewer transitions and joints), low pressure drop terminals and plenum returns.  Complete the fan power equation by selecting efficient motors and drives, or  efficient variable speed motors and drives for part load energy savings. A fan running at one-half the design airflow operates with one-eighth the power consumption.

RSKN_Go_Green_LogoFor 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.

High Performance Air Systems – History of Ducted and Ductless Systems

Ducted or non ducted air systems

Ducted air systems are used in the majority of comfort cooling applications in North  America. In contrast, ductless refrigerant systems in Asia, and ductless water systems in Europe dominate their respective HVAC markets. These practices reflect the historical evolution of air conditioning in each market.

Use of the coal-fired basement furnace evolved in the in the late 19th and early 20th century in North America to keep coal dust and storage away from occupied spaces.  Coal was used for coal-fired boilers  or coal-fired furnaces.  Older buildings in the Northeastern part of the US used hydronic heat distributed via radiators.  District steam in New York City and other major cities gave rise to ‘cast-iron’ and the pipefitting trade.  With the invention of air conditioning, radiators were replaced with two to four pipe fan coil systems and existing pipe chases were upgraded to handle chilled water as well as hydronic heat.  This expertise and influence for water-based systems still exists today in the Northeast US.

Different factors influenced construction practices with the western expansion of the US.   Both wood and land was plentiful.   Demand for detached multi-room single-family homes grew at a rapid pace.   It became common practice to duct heated air from the basement furnace to all the rooms – first by gravity and then forced air.  Wood construction was common and the space between the wall studs and floor/ceiling joists became the ductwork.  After WWII, contractors invested heavily in duct-fabrication to satisfy the new construction demand for housing and quick-build commercial applications. When the market for central air conditioning began during the 1960’s and 70’s, it was easy to add an “A” coil (evaporator) to the top of the furnace and add a condensing unit outside. Because residential and commercial practices influence each other, the use of a common duct for both heating and cooling carried over to all commercial building types as well. DX (direct expansion) Rooftop VAV (variable air volume) exploded in the 80’s as the demand for cost-efficient and fast installation increased dramatically.

Air Conditioning CondensersEurope and Asia’s HVAC evolution was driven by different construction practices and constraints.  Europe’s path was/is similar to that of the Northeast US.  Older buildings (and there are a lot of them in Europe) allowed no provision for ductwork – masonry construction had no hollow walls.  These buildings were heated using piped radiation systems.    Contractors developed a strong pipe-fitting culture and engineers developed tremendous knowledge of designing water-based systems.   Hence, non-ducted water-based systems are still preferred today.

Asian apartments were/are predominantly one or two room.  Through the 1950’s, many were heated by a single kerosene heater. Again, construction was/is poured concrete or concrete blocks with no hollow walls. Central heating using hydronic radiators were rare. The window unit boom in the 1960’s and 70’s provided cooling and safer electric-strip heating in one device to satisfy the needs of these small living quarters that had no provision for piping or ductwork.  In the late 1970’s and 1980’s, the evaporator/heating and compressor/condenser were separated into indoor and outdoor components– hence, mini-split.  This was not only a quieter alternative to the ‘window-shaker’, but gave the owner back his/her outdoor view.  The next logical evolution was multiple DX fan coils from one condensing unit for commercial and multi-family applications.   VRF split systems with multiple indoor units were introduced for multi room applications.

Ducted or Non-ducted?

Ducted SystemAs the above history lesson shows, the driver for ducted or non-ducted has nothing to do with efficiency.  The driver has to do with simple evolution of HVAC in relation to cultural building market drivers.

When deciding which system to use, each has advantages and disadvantages dependent upon application, climate, building construction, and other factors.  Multi-family housing, dormitories, and hotel applications all are construction-types where a common air return is not permitted.  This  is the logical market for non-ducted products.  VRF provides an alternative to hydronic fan coil systems, water-source heat pumps, and PTAC’s.  Existing masonry buildings – where ducting may be too expensive to add – also is a sensible solution for non-ducted products. Several building types require a mix of system types. Health care applications are an excellent example of a mixed-use system approach (e.g., fan coils for patient rooms, ducted for common areas).

For other commercial applications – e.g., schools, education, offices, retail/restaurants, theaters, casinos, factories – a high performance ducted system makes sense from a total life-cycle cost standpoint.  Ducted systems offer lower installed cost, better efficiency (e.g., cooling with compressor-free outside air) and code compliant ventilation within the same system.

RSKN_Go_Green_LogoFor 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.