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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.

Guide for Facility Managers on the Testing and Maintenance of Fire Dampers

fire damperA fire damper can be defined as “a device installed in ducts and air transfer opening of an air distribution or smoke control system designed to close automatically upon detection of heat. It also serves to interrupt migratory airflow, resist the passage of flame, and maintain the integrity of the fire rated separation.” Its primary function is to prevent the passage of flame from one side of a fire-rated separation to the other.

The significant protection capabilities of fire dampers to life and property are now widely recognized by Facility Managers throughout the United States. More and more Authorities Having Jurisdiction (AHJ’s) and building owners are requiring fire dampers to be operational tested and maintained on a regular basis.

AHJ’s are requiring operational tests to determine if the damper will function when needed in order to resist the spread of fire. Operational testing normally involves removing or melting the fusible link and letting the damper close. Once the damper has proven to close, it is reopened and the fuse link replaced. All the dampers installed in a building must be tested prior to occupancy and again 1 year later under normal operating conditions. Reference NFPA 80 and NFPA 105 for more information.

Applicable Standards

NFPA 80 is the National Fire Protection Association standard that regulates the installation and maintenance of assemblies and devices used to protect openings in walls, floors and ceilings against the spread of fire and smoke within, into, or out of buildings.

NFPA 105 is the standard which prescribes the minimum requirements for smoke door assemblies and smoke dampers that are used as a means to restrict the flow of smoke though openings to provide safety to life and protection of property.

Fire Dampers must meet the UL555 Test Standard. UL (Underwriters Laboratories) states that the requirements of UL555 cover fire dampers that are intended for use where air ducts penetrate or terminate at openings in walls or partitions; in air transfer openings in partitions; and where air ducts extend through floors as specified in the standard for installation of air-conditioning and ventilating systems, NFPA 90A.

Testing and Maintenance

AMCA presents a valuable guide for commissioning and periodic performance testing of fire, smoke and other life safety related dampers. This guide provides recommendations for the proper commissioning of fire and life safety related dampers and details the appropriate intervals and methods for performing periodic performance testing of these dampers. This guide can be downloaded for free from AMCA’s website below.

AMCA Guide for Commissioning and Periodic Performance Testing of Fire, Smoke and Other Life Safety Related Dampers

To the facility manager operational tests and regular maintenance can present a couple of challenges:

  1. Most fire dampers are installed in areas of the building that are not easily accessible. Fire dampers are installed in penetrations of fire rated walls and floors as required by the building code and access to the damper itself is normally through an improperly sized access door.
  2. Fire dampers can be extremely difficult to test and reset due to their design (all manufacturers’ utilize the same basic curtain type design). There are two main types of fire dampers: dynamic fire dampers and static fire dampers. Dynamic fire dampers have been UL tested and proven to close against system air pressure and velocity. Static fire dampers, on the other hand, are UL tested but have not been proven to close against system air pressure and dynamic fire dampervelocity. The main difference between the two designs is dynamic dampers (in most cases) utilize springs to pull the curtain closed against the air pressure and velocity while static dampers rely solely upon gravity to pull the curtain closed (static dampers designed for floor installation utilize closure springs). The spring shape and size determine the air pressure and velocity against which the dynamic fire damper closes.

Dynamic fire dampers are becoming more popular with designers as dynamic dampers may be used in either a static system (fans off) or dynamic system (fans on) while static dampers can only be used with static systems.

Limited access and closure springs do not make dynamic fire dampers testing and maintenance friendly despite being life and property friendly as they are guaranteed to close if properly applied and installed.

A solution to the operational acceptance testing problems is to know the testing requirements beforehand. Coordinate with the AHJ and determine what they will accept for testing procedures.

Since dynamic dampers are proven to close, the solution may be a simple installation inspection to make sure the dampers are installed properly with no obstructions.

A solution to the maintenance testing is not so simple. Maintenance should be performed per NFPA80 and NFPA 105 requirements: “Each damper shall be tested and inspected after the damper is installed, then one year after installation. The maintenance testing and inspection frequency shall then be every 4 years, except in hospitals, where the frequency shall be every 6 years.”

Motorized fire damperMore often than not, the building will be occupied and access to the damper remains a problem; however the use of a motorized fire damper that can be operated from a remote, easily accessible location and can be equipped with position indication for operation verification. A motorized fire damper can be more easily maintained compared to a standard dynamic fire damper and contributes to maintenance and insurance savings. All motorized fire dampers are dynamic rated and may be utilized in place of any static or dynamic curtain blade fire damper.

Dynamic, multiple blade fire dampers provide another solution to the access and maintenance issues posed by the dynamic curtain blade dampers. Multiple blade fire dampers are easy to both test and reset since the blades can be operated and held open via a hand lever or a pair of pliers while the fuse link is replaced. An additional solution for round ducts is the use of a true round fire damper. Round fire damper allows the fusible link to be replaced easily then the damper can be adjusted to its full-open position.

Summary

Testing and maintenance of fire dampers, especially dynamic, curtain fire dampers, can be extremely difficult. There are, however, alternative types of dynamic fire dampers that make testing and maintenance easier. The cost of these other dampers is typically greater than standard dynamic fire dampers but savings can be easily realized in other areas like maintenance and insurance. Before designing around “standard” curtain type dynamic fire dampers, check with the Authorities Having Jurisdiction (AHJ’s) and the building owner to determine the testing and typical multi-blade dynamic fire damper maintenance requirements.

Ruskin Wireless InspectorRuskin Damper Testing Solutions

Ruskin can present a solution to your testing problems, our patented Wireless Damper Inspector system. Utilizing radio frequency, this remote control system cycles actuators of all life safety motorized dampers especially those that are installed in hard to reach or even inaccessible locations. Ruskin Wireless Damper Inspector satisfies NFPA requirements* for both initial and periodic testing of life safety dampers.

Ruskin Classic InspectorRuskin’s Classic Inspector™ consists of a Panel PC, UPS and pre-loaded software. The Panel PC communicates with damper interfaces to provide intelligent monitoring of motorized dampers and manual fire dampers. The data network cabling represents a substantial cost reduction when compared with conventional systems.

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.

Useful References

Miami-Dade County Approval Tests for Louvers

Louver Building Miami DadeThe South Florida Building Code (SFBC) states that products installed on the exterior of buildings must be designed to withstand the severe conditions produced by hurricanes. However, the widespread failure of various building products during Hurricane Andrew in 1992 identified a need for stronger code enforcement. Recognizing that standardized testing and product control could assist enforcement, the Metro-Dade County (later changed to include all of Miami-Dade County) Florida Building Code Compliance Office (BCCO) developed a series of test protocols that subject products to the rigors of hurricane wind and rain conditions.

Miami DadeTo gain Miami-Dade County Approval, louvers may be required to pass as many as four different tests — three are structural and one measures wind driven rain penetration resistance. These tests are referred to as PA’s or Protocol and Application Standards.

PA-100(A): Wind Driven Rain Penetration Test

The Building Code Compliance Office (BCCO) requires this test if the room the louver is installed in is designed to be dry (room is not designed to drain water and/or houses items that are not water resistant). This test subjects the louver to high velocity winds and heavy simulated rainfall. Using a wind generator and water jets that inject the equivalent to 8.8″ per hour rainfall into the airstream, 15 minute tests are run at wind velocities of 35, 70, and 90 mph. The final 110 mph test is performed for 5 minutes. The louver must allow no water penetration at 35 and 70 mph, and only .05% penetration at 90 and 110 mph.

PA-202: Uniform Static Air Pressure Test

If a louver is installed in a room that can drain water and houses water resistant items, the wind driven rain test is not required. Instead, the PA-202 test is performed. In this procedure, the louver is installed in a chamber and uniform static air pressure is applied in positive and negative directions. Several pressure levels are applied in increasing magnitude until a load equal to 1.5 times the design windload is attained. Pressures are sustained for 30 seconds. The deflection of blades, frames and supports is measured during the test and the amount of recovery is checked afterwards. Throughout the test the anchorage system is also monitored for failure. Design windloads for hurricane applications can produce static pressures in excess of 28″ w.g. If the room is considered a closed structure that cannot withstand this pressure or if it houses equipment that cannot handle the pressure, the BCCO code requires the louver/damper assembly be subjected to the PA-201 and PA-203 tests.

PA-201: Large Missile Impact Test

Impact on Miami Dade LouverThis test simulates wind-driven debris that is often present in hurricanes. In the test, the louver assembly is impacted with a 2″x 4″ board weighing 9 lbs. and traveling at approximately 34 mph. At least three separate impacts are conducted and the louver must prevent the board from both penetrating the assembly or creating a significant opening.

PA-203: Cyclic Wind Pressure

This test is conducted only after the Missile Impact Test has been done. By simulating the forces applied to a louver by repeated severe wind gusts, this test exposes possible weaknesses in the assembly created by the missile impacts. In this test, the louver assembly is installed in a chamber similar to the Uniform Pressure test. However, the pressures are applied for only a few seconds and repeated several hundred times. Pressure is increased until 1.3 times the design windload is achieved. As in the PA-202 procedure, the deflection of the components and the anchorage system are examined.

Miami Dade Louver Cross SectionRuskin’s Hurricane Louvers

Ruskin’s Hurricane Louvers are designed to exceed impact resistance and windload requirements with predesigned proven installation methods. Ruskin was the first manufacturer to gain Miami-Dade County approval for louvers. These louvers are built to withstand up to 160 psf on some products based upon the criteria in TAS 201, 202 and 203 as well as AMCA 540/550.

Hurricane Louver Products

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.

High Performance Air Systems – In Conclusion

building envelopesToday’s tight building envelops with high occupant density and internal loads require year-round cooling in interior zones.  High performance air systems offer free cooling from airside economizers at lower outside temperatures, while VRF systems must run the compressors at all outdoor air [latent too]conditions to satisfy cooling demand.  VRF proponents often talk about energy-recovery.  However, that requires simultaneous compressor-heating and compressor-cooling operation (compression cycle).  Contrast this to a modern airside economizer used with HPAS.  Additionally, HPAS offers further part load energy saving measures using advanced control technologies which include ventilation optimization based on fresh air demand by zone, comparative enthalpy economizers with remote indication, supply air temperature reset tied to measured system demand and optimum start/stop.

As with VRF, HPAS are also available with variable compressors and fans.  This combined with the refrigeration/heating energy saving options not available with VRF save even more energy. These options include the ability to provide lower cost, and efficient gas heating systems, trending and automated reporting of total system diagnostics, user-specific building automation control strategies, measurement and control of airflow, thermal energy storage in the building structure (pre-cooling with economizer-flush at night) can reduce peak demand and shift the cooling load to times of cooler OA.

The most publicized comparison of energy use of between a ducted air system and a VRF system  is the ASHRAE Headquarters Building in Atlanta, GA. The building uses three separate HVAC systems: a variable refrigerant flow (VRF) system for spaces on the first floor, a ducted ground source heat pump (GSHP) system, primarily for spaces on the second floor, and a dedicated outdoor air system (DOAS), which supplies outside air to both floors.  The VRF system consumed 61% more energy than the ducted GSHP.

2012 Energy usage for GSHPs – 24,430.89 kWh (Jan – Dec)
Heating / cooling area for GSHPs – 15,558 sq. ft.
GSHP = 1.57 kWh / sq. ft.

Energy usage for VRF – 46,066.54 kWh (Jan – Dec)
Heating / cooling area for VRF – 18,226 sq. ft.
VRF = 2.53 kWh / sq. ft.

VRF consumed 61% higher annual kWh/sq. ft. in 2012
(2.53-1.57)/1.57* 100 = 61%

ASHRAE 15

gas monitorRisk of refrigerant leakage in occupied spaces is a safety issue for VRF but not for high performance air systems where refrigerant is located in an equipment room, rooftop unit, or minimal line-runs. Users must be cognizant of ASHRAE 15 requirements. The space served by each zone must be large enough to disperse the entire system refrigerant charge per ANSI / ASHRAE Stds. 15 and 34 and local codes.  A maximum of 25 lbs of R-410A per 1000 cuft of room volume is allowed for non-institutional spaces. Transfer ducts between rooms may be required. ASHRAE 15 refrigerating machinery room requirements also require venting of fusible plugs. When any system contains more than 110 lbs. of refrigerant these fusible plugs must be discharged “to the atmosphere at a location not less than 15 feet above adjoining ground level and not less than 20 feet from any window, ventilation opening, or exit”

High performance air systems require no scheduled maintenance in occupied spaces. For VRF indoor unit filter replacement, coil cleaning, and visual inspection of condensate drain must be done for every indoor fan coil on a scheduled basis. Both maintenance above the ceiling, condensate pan overflow risk and refrigerant leaks can result in ceiling damage and inconvenience to occupants.

Equipment performance is certified by ASHRAE and AHRI for high performance air systems and assures owners that performance meets specified levels.   ASHRAE certified air performance covers fan efficiency grades, sound levels and ducted air system leakage. AHRI certified thermal performance covers refrigeration system efficiency.

Summary

High performance ducted air systems overcome many of the disadvantages of non-optimized ducted systems. And compared to VRF, HPAS systems provide better comfort, meet ventilation codes, have a lower initial cost, consume less energy, carry no refrigerant risk, require less maintenance and provide performance certified by AMCA, AHRI.

VRF and other non-ducted systems certainly have their application as described herein. Additionally, they make sense for many mixed-use applications.   However, when system designers have a choice, it is easy to see why ducted systems – especially HPAS ducted systems – are North America’s number one choice for comfort cooling.

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.