New Design Trends for Air Conditioning Installations in Data CentresBest Practice for trouble-free and efficient operation of the Data Center cooling systemKURT JÜRGEN PLÖTNER Director Global Product Sales & MarketingSTULZ GmbH May 2009Best Practice - Data Centre Cooling1New Design Trends for Air Conditioning Installations in Data CentresBest Practice • What is precision air conditioning ? • Why energy efficient precision air conditioning ? • Requirements of the IT-equipment and the data-centre • Elements influencing the data-centre cooling efficiencyMay 2009Best Practice - Data Centre Cooling2New Design Trends for Air Conditioning Installations in Data CentresWhat is Precision Air Conditioning ?May 2009Best Practice - Data Centre Cooling3New Design Trends for Air Conditioning Installations in Data CentresDefinition Precision Air Conditioning (PAC) or Computer Room Air Conditioning (CRAC) Close control units are able to maintain defined, constant and therefore precise temperature and humidity conditions in the room. The tolerances for room temperature and humidity are controlled in a small band. These tolerances are usually as follows: - Temperature: +/- 1K - Humidity: +/- 5% => The units have to: • Cool • Reheat • Humidify • DehumidifyMay 2009Best Practice - Data Centre Cooling4New Design Trends for Air Conditioning Installations in Data CentresDefinition Precision Air Conditioning (PAC) or Computer Room Air Conditioning (CRAC) In addition the air is filtered with a high grade of air filter.The cooling capacity is offered typically as >90% sensible cooling capacity – this portion of the total cooling capacity is able to reduce the temperature. The latent cooling capacity portion typically <10% is able to reduce the humidity in the room – the dehumidification is a control function. The absorbed energy of a close control air conditioning system is used to reduce the temperature of the room !!! May 2009Best Practice - Data Centre Cooling5New Design Trends for Air Conditioning Installations in Data CentresCooling Capacity – What does total and net sensible cooling capacity mean? InputFunctionConditions98,5 kW Total Cooling CapacityAirflow 24.000 m³/hReturn Air 24° C; 45 % r. H. 8.3 g water / kg air93,5 kW Sensible Capacity (cooling) and 5 kW Latent Capacity (dehumidification)Temperature Decrease 12.0° C and Humidity Decrease 0.3 g / kg Cooling Air 12.0° C; 92 % r. H. 8.0 g water / kg air5,9 kW Heat Rejection Fan absorbed power converts to heat87,6 kW Net Sensible Cooling CapacityMay 2009Temperature Increase 0.8° CExample: ASD 1062 ABest Practice - Data Centre CoolingCooling Air (supply air) 12.8° C; 87 % r. H. 8.0 g water / kg air6New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Application•Air conditioning for technical applicationsCooling capacity•4 to 200 kWMay 2009Best Practice - Data Centre Cooling•Air conditioning for human requirements•2 to 30 kW7New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Environmental requirements•Electronic requirements•Human requirementsSource: ASHRAE» A much smaller band has to be controlled more precisely !! May 2009Best Practice - Data Centre Cooling8New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Sensible heat ratio•> 90 %•50 to 60 %The sensible part of the cooling capacity reduces the temperature, while the latent part reduces the humidity. Comfort air conditioning units use up to 50% of their capacity for dehumidification, whereas precision air condition units convert more than 90% of their energy into cooling capacity. May 2009Best Practice - Data Centre Cooling9New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Temperature control••+/- 1K+/- 3KIT-equipment only works reliable and without faults within a relatively narrow temperature range. Precision air conditioning units ensure optimum temperature accuracy with maximum tolerances of +/- 1K, while comfort units can normally deviate from the set value by as much as +/- 3K. May 2009Best Practice - Data Centre Cooling10New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Humidity control•Controlled humidification and dehumidification•Unregulated dehumidification for comfortable cooling(+/- 5% relative humidity)Unlike comfort air conditioning units, precision air conditioning units can feature proportional controlled and accurate humidification (+/- 5%), as too much humidity can lead to corrosion and condensation, while too little can cause static charges, data loss and damage to hardware.May 2009Best Practice - Data Centre Cooling11New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Airflow and filtration• •200 to 300 m³/h per kW High grade of air filtration (minimum G4)• •100 m³/h per kW Low grade of air filtrationPrecision air conditioning units filter and circulate approx. 3 times the amount of air as comfort units with the same rated capacity. That means they reliably are able to dissipate isolated thermal loads even from distant corners of a room. May 2009Best Practice - Data Centre Cooling12New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Diversity of options•High, due to individual productionOperator controls•Technical, many parametersMay 2009Best Practice - Data Centre Cooling••Low, due to mass productionSimple, few parameters13New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Method of operation•Permanent operation (8.760 hours per year)•Cyclical operation (1.200 hours per year)Comfort air conditioning units mainly operate in summer and only a few hours a day. By contrast, precision air conditioning units need to be available whenever the electronic equipment to be cooled is in operation. This is normally the case for 24 hours a day, 365 days a year. May 2009Best Practice - Data Centre Cooling14New Design Trends for Air Conditioning Installations in Data CentresPrecision and comfort A/C-units comparison Summary: If you have to cool electronic equipment that has to be in operation 24 hours a day and 365 days a year – the only choice is a precision air conditioning unit. Only a precision air conditioning unit is able to control the room temperature and humidity exactly according to the demand of the IT-equipment.May 2009Best Practice - Data Centre Cooling15New Design Trends for Air Conditioning Installations in Data CentresWhy Energy Efficient Precision Air Conditioning?May 2009Best Practice - Data Centre Cooling16New Design Trends for Air Conditioning Installations in Data CentresThe Need for Energy Efficient Data Centres Some headlinesIn general: One 20 MW data-centre and 80.000 households (“western standard”) consume the same energy a year. Germany: Altogether approximately 50.000 server rooms and data-centres consumed 10,1 TWh (= 10.100.000.000 kWh) in 2008 (equivilant to 6.4 million tons of CO2). Worldwide: It is estimated that server rooms and data-centres consumed about 123 billion kWh in 2005. If the status quo continues, by 2011, data-centres will consume about 216 billion kWh of energy. This is approx. 1 to 1,3% of the total power consumption. May 2009Best Practice - Data Centre Cooling17New Design Trends for Air Conditioning Installations in Data CentresThe Need for Energy Efficient Data CentresMay 2009Best Practice - Data Centre Cooling18New Design Trends for Air Conditioning Installations in Data CentresThe Need for Energy Efficient Data Centres Considering the „buisiness-as-usual“ scenario it would mean that in 2013 in Germany about 2,2 billion € have to be paid for energy in datacentres. Taking into account the „moderate-efficiencyincrease“, what does mean that an energy saving of 10% in all datacentres is possible, the number would be 1,4 billion €.May 2009Best Practice - Data Centre Cooling19New Design Trends for Air Conditioning Installations in Data CentresEnergy flow through the Data Centre PUE Example: Having a facility that uses 100.000 kW of total power of which 80.000 kW is used to power the IT equipment, would generate a PUE of 1.25. DCE (DCiE) Example: Having that same facility that uses 100.000 kW of total power of which 80.000 kW is used to power the IT-equipment, would generate a DCiE of 0,8. => That means, the lower the PUE or the higher the DCiE the more power can be used for the IT load and the more efficient the cooling of the data-centre.May 2009Best Practice - Data Centre Cooling20New Design Trends for Air Conditioning Installations in Data CentresEnergy flow through the Data Centre …so: Why energy efficient cooling? Lighting 1% 100%Switchgear/Generator; 1%90%• Save operating cost throughout the data centre's lifetimeUPS 18%80%PDU 5%70%• Get more IT capacity out of IT Equipment 30%60%your data centre at a given available power by reducing power use of secondary physical infrastructure50%CRAC 9%40%Humidification 3%45 % Air conditioning30%20%Chiller 33%10%0% 1May 2009Best Practice - Data Centre Cooling21New Design Trends for Air Conditioning Installations in Data Centres…so: Why energy efficient cooling?Source: Lawrence Berkeley National Lab; Data centre energy benchmark case studies May 2009Best Practice - Data Centre Cooling22New Design Trends for Air Conditioning Installations in Data CentresRequirements of the IT-equipment and the data-centreMay 2009Best Practice - Data Centre Cooling23New Design Trends for Air Conditioning Installations in Data CentresTarget of computer air conditioning: Cold supply air in front of the rack at any time of the year for trouble-free operation of the IT-equipmentMay 2009Best Practice - Data Centre Cooling24New Design Trends for Air Conditioning Installations in Data CentresTarget of computer air conditioning: Cold supply air in front of the rackSource: INTELSource: HPhorizontal air distribution through the rackMay 2009Best Practice - Data Centre Cooling25New Design Trends for Air Conditioning Installations in Data CentresServer air inlet temp. !!Source: ASHRAE May 2009Best Practice - Data Centre Cooling26New Design Trends for Air Conditioning Installations in Data CentresThe updated ASHRAE recommended Environmental Envelope:Limits:• • • •May 2009Best Practice - Data Centre CoolingMax. room temp. Min. room temp. Max. room hum. Min. room hum.27°C 18°C 60% 25%27New Design Trends for Air Conditioning Installations in Data CentresEquipment requirements – Air conditions return airHeat load QRecommendation for return air 26 °C ; 40 % r. H.Only reachable by ΔT of approx. 8Kand supply conditions: 18 °C ; ~ 80 % r. H.supply air May 2009Best Practice - Data Centre Cooling28New Design Trends for Air Conditioning Installations in Data CentresEquipment requirements - Airflow return airDesign air volumeQ VL = ρ A * cpA * ΔT Heat load QVL = Q = ρA = cpA =Air volume [m³/s] Heat load [kW] Density [kg/m³] Specific heat capacity of air [kJ/kgK] ΔT = Difference between discharge and supply temperature [K]supply air Reference value approx. 300 m³/h per kW May 2009Best Practice - Data Centre Cooling29New Design Trends for Air Conditioning Installations in Data CentresEquipment requirements - Filtration return air Filtration of the circulated air is required.Heat load QEquipment has to be protected against dust from outside air, walls, ceiling and the raised floor. Suggested: filter class EU4 Mainfilter EU5 or Pre-filter EU2, EU5 Mainfiltersupply air May 2009Best Practice - Data Centre Cooling30New Design Trends for Air Conditioning Installations in Data CentresEquipment requirements – Relative Humidity The printed circuit boards (PCBs) have to be protected against: - Electrostatic discharge (ESD) - Conductive anodic filament (CAF) CAF is caused by too high humidity, the relative humidity in the room therefore should not exceed 60% ESD is caused by too low humidity, the relative humidity in the room therefore should not be lower than 25%May 2009Best Practice - Data Centre Cooling31New Design Trends for Air Conditioning Installations in Data CentresElements influencing the Data Centre Cooling efficiencyMay 2009Best Practice - Data Centre Cooling32New Design Trends for Air Conditioning Installations in Data CentresElements influencing the Data Centre Cooling Efficiency Ambient Conditions (Location) Free CoolingRoom TemperatureAir DistributionRoom HumidityRefrigerant Charge Raised Floor HeightFilter StatusPerforated Tile QuantityInstalled Options Redundancy LevelPerforated Tile Opening FactorPump Technology Leakage Airflow RatePipe Sizing RefrigerantWater TemperaturesDimensions Part Load Behaviour Fan TechnologyHeat Exchanger SurfaceDrycooler Size May 2009Filter SurfaceBest Practice - Data Centre Cooling33New Design Trends for Air Conditioning Installations in Data CentresElements influencing the Data Centre Cooling Efficiency 1. The room:• • • • • • • • •Air distribution The raised floor Raised floor height Perforated tile quantity Perforated tile opening factor Airflow leakage rate Pressure in the raised floor Room temperature Room humidityMay 20092. The CRAC-unit:• • • • • • • • • • • •Return air temperature Return air humidity Water temperatures Type of expansion valve Heat exchanger surface Part load behaviour Filter surface / status Fan technology Unit dimensions Refrigerant / refrigerant charge Installed options Standby-unit operationBest Practice - Data Centre Cooling34New Design Trends for Air Conditioning Installations in Data Centres1. The roomMay 2009Best Practice - Data Centre Cooling35New Design Trends for Air Conditioning Installations in Data Centres• Air distribution <= • The raised floor • Raised floor height • Perforated tile quantity • Perforated tile opening factor • Airflow leakage rate • Pressure in the raised floor • Room temperature • Room humidityMay 2009Best Practice - Data Centre Cooling36New Design Trends for Air Conditioning Installations in Data CentresAir distribution The parameters of the air circuit: Reduction of air side pressure drop 1 2External statical pressure3Installed equipment „supply air“4Quantity open tiles5Air flow leakage rate6Air flow77Filter/Heat exchangerInstalled equipment „return air“6 1 5431 May 2009to 72: reduction of air side pressure drop = reduction of fan power consumption Best Practice - Data Centre Cooling37New Design Trends for Air Conditioning Installations in Data CentresAir distribution 1 to 7The parameters of the air circuit: A pressure drop reduction of 10 Pa in the air circuit means:- 2 to 3% reduction of EC-fan power consumption - 1 to 2% reduction of power consumption of a standard radial fanCaution: Reduction of air side pressure drop: Yes, but the raised floor has to be pressurized. For an even air distribution in the raised floor an overpressure of approximately 20Pa is needed. The open tiles have to be balanced and a sufficient pressure has to be ensured.May 2009Best Practice - Data Centre Cooling38New Design Trends for Air Conditioning Installations in Data CentresAir distribution Further parameters of the air circuit: Separation of cold and hot air28°C 8 Avoiding of bypasses 99 Rack-design8ΔΤ1010 Installed equipment18°C Separation of cold and hot air = max. ΔΤ = max. energy efficiency! May 2009Best Practice - Data Centre Cooling39New Design Trends for Air Conditioning Installations in Data CentresAir distribution Air Cooling – A matter of a Defined Air PathHot/Cold Aisle Concept• Cold supply air distribution only in the cold aisles • Warm return air only in the hot aisles • Open tiles only in the cold aisle • Risk of mixing cold and hot air is high May 2009Best Practice - Data Centre Cooling40New Design Trends for Air Conditioning Installations in Data CentresAir distribution Air Cooling – A matter of a Defined Air PathDucted Return Air Concept• Cold supply air distribution only in the cold aisles • Warm return air only in the hot aisles into a false ceiling • Open tiles only in the cold aisle • Risk of mixing cold and hot air is lower May 2009Best Practice - Data Centre Cooling41New Design Trends for Air Conditioning Installations in Data CentresAir distribution Air Cooling – A matter of a Defined Air PathDucted Supply and Return Air Concept• Cold supply air into ducts fitted to the supply air side of the racks • Warm return air through ducts fitted to the exhaust side of the racks • Open tiles only in the area of supply air ducts • No risk of mixing cold and hot air May 2009Best Practice - Data Centre Cooling42New Design Trends for Air Conditioning Installations in Data CentresAir distribution Air Cooling – A matter of a Defined Air PathCold Aisle Containment• Cold supply air distribution only in the cold aisles • The cold aisle is separated from the hot aisle • Warm return air only in the hot aisles into a false ceiling • Open tiles only in the cold aisle • No risk of mixing cold and hot air May 2009Best Practice - Data Centre Cooling43New Design Trends for Air Conditioning Installations in Data Centres• Air distribution • The Raised floor • Raised floor height • Perforated tile quantity • Perforated tile opening factor • Airflow leakage rate • Pressure in the raised floor • Room temperature • Room humidityMay 2009Best Practice - Data Centre Cooling<= <= <= <= <= <=44New Design Trends for Air Conditioning Installations in Data CentresThe Raised Floor = Supply Air Duct ! Raised Floor void according to Room size and Load Density Sufficient Pressure in order to deliver a equal air volume pattern through the whole Room, cable sealing for power and IT Cabling Avoid Installation such as Pipes, Cable Trays etc. Cable Management IT Cabling „from above“ especially for Rooms with limited Floor Void Unused IT cable should be removed Each barrier creates a pressure drop and results in higher energy consumption of the CRAC unitsMay 2009Best Practice - Data Centre Cooling45New Design Trends for Air Conditioning Installations in Data CentresRaised floor – unused cables should be removed…May 2009Best Practice - Data Centre Cooling46New Design Trends for Air Conditioning Installations in Data CentresRaised floor – For supply air (and cables/pipes)May 2009Best Practice - Data Centre Cooling47New Design Trends for Air Conditioning Installations in Data CentresLeakage Airflow - …to be avoided…May 2009Best Practice - Data Centre Cooling48New Design Trends for Air Conditioning Installations in Data CentresRaised floor height Rule of thumb: The higher, the better ! Tile number1 2 3 4 5 6 7 8 9 10 11 12 13 14 15A certain obstacle free area is required for a proper supply of cold air to any area of the room ! May 2009Best Practice - Data Centre Cooling49New Design Trends for Air Conditioning Installations in Data CentresRaised floor pressureTile number1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Only a raised floor with sufficient height and perforated tiles with limited openings allow an even air distribution !!!Source: IBM May 2009Best Practice - Data Centre Cooling50New Design Trends for Air Conditioning Installations in Data Centres• Air distribution • The Raised floor • Raised floor height • Perforated tile quantity • Perforated tile opening factor • Airflow leakage rate • Pressure in the raised floor • Room temperature <= • Room humidity <=May 2009Best Practice - Data Centre Cooling51New Design Trends for Air Conditioning Installations in Data CentresReturn Air temperature ≠ Room temperatureReturn Air 24°C 24° I M P O R T A N T !!! Return Air≠Room 21°C 21° Depending on heat load the return air temp. is at least 2 - 3K higher than room temperatureSupply AirMay 200916°C 16°Best Practice - Data Centre Cooling52New Design Trends for Air Conditioning Installations in Data CentresBlanking plates in the rack – separation of cold and hot aisle in the rackSource: HP informs: How to Meet “24 by Forever” Demands of Your Data CentrePrevent internal hot air recirculation by sealing the front of cabinets with blanking plates, including empty areas in the equipment – mounting surface, between the mounting rails, and the edges of the cabinets (if necessary). May 2009Best Practice - Data Centre Cooling53New Design Trends for Air Conditioning Installations in Data CentresPlanning vs. RealityMay 2009Best Practice - Data Centre Cooling54New Design Trends for Air Conditioning Installations in Data Centres2. The Close control unitMay 2009Best Practice - Data Centre Cooling55New Design Trends for Air Conditioning Installations in Data CentresDesign of the CRAC unit: Build in Energy Efficiency Target:• Reduction of fan power consumption• Reduction of compressor power consumption Main aspects:• Maximisation of heat exchanger surface• Maximisation of filter surface• Reduction of airside pressure drop• Fan technology, reduction of the fan speed May 2009Best Practice - Data Centre Cooling56New Design Trends for Air Conditioning Installations in Data CentresEnergy and cost saving by reducing power consumptionMay 2009Best Practice - Data Centre Cooling57New Design Trends for Air Conditioning Installations in Data Centres2. The close-control-unit:• Fan technology <= • Part load behaviour • Standby-unit operation • Filter surface / status • Heat exchanger surface • Unit dimensions • Return air temperature • Return air humidity • Water temperatures • Type of expansion valve • Refrigerant / refrigerant charge • Installed optionsMay 2009Best Practice - Data Centre Cooling58New Design Trends for Air Conditioning Installations in Data CentresInfluence of the fan technology on the power consumptionCentrifugal fanvs.Example: CSD 431 A • Air volume:EC-fan Example: ASD 451 A13.000 m³/h• Air volume:13.000 m³/h• Total cooling cap.: 44,0 kW• Total cooling cap.: 43,9 kW• Fan power cons.:• Fan power cons.:3,9 kW2,3 kW• Reduction of fan power consumption by 42% • Savings: 1.822,- €/year @ 0,13 €/kWh May 2009Best Practice - Data Centre Cooling59New Design Trends for Air Conditioning Installations in Data CentresInfluence of the fan technology on the power consumption …but, EC-technology is much more than efficiency…••Scalable air volume setting via Controller on demand Direct drive technology, no belts+ + + + +• May 2009Low vibration Best Practice - Data Centre Cooling+Easy adaption to changing space conditions Additional energy savings Reduced noise levels Long and maintenance-free operation No abrasion, No belt dust , No additional filtration neededQuiet running AC unit 60New Design Trends for Air Conditioning Installations in Data Centres2. The close-control-unit:• Fan technology • Part load behaviour <= • Standby-unit operation <= • Filter surface / status • Heat exchanger surface • Unit dimensions • Return air temperature • Return air humidity • Water temperatures • Type of expansion valve • Refrigerant / refrigerant charge • Installed optionsMay 2009Best Practice - Data Centre Cooling61New Design Trends for Air Conditioning Installations in Data CentresInfluence of the fan technology on the power consumption EC-fan part load behaviour100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% AirflowMay 2009Absorbed PowerBest Practice - Data Centre Cooling1/2 Airflow 1/8 Absorbed PowerAirflowAbsorbed Power62New Design Trends for Air Conditioning Installations in Data CentresInfluence of the fan technology on the power consumption EC-fan part load behaviour (CW-Standby-Management) Sample: 4x ASD1900CW at 26°C/40% Water 10/15°CAirflow: 3x 39.000 m³/h Fan power = 3x 12,6 kW = 37,8 kW Lpa,2m = 3x 71,6 dB(A) = 76,4 db(A)Standby3x 146,8 kW = 440,4 kW net sensibleAirflow: 4x 29.000 m³/h Fan power = 4x 5,3 kW = 21,2 kW Lpa,2m = 4x 50,8 dB(A) = 56,8 db(A) 4x 114,6 kW = 458,6 kW net sensible=> Energy savings: 16,6 kW x 8760h x 0,13 = 18.904 €/year @ 0,13 €/kWh May 2009Best Practice - Data Centre Cooling63New Design Trends for Air Conditioning Installations in Data Centres2. The close-control-unit:• Fan technology • Part load behaviour • Standby-unit operation • Filter surface / status <= • Heat exchanger surface • Unit dimensions • Return air temperature • Return air humidity • Water temperatures • Type of expansion valve • Refrigerant / refrigerant charge • Installed optionsMay 2009Best Practice - Data Centre Cooling64New Design Trends for Air Conditioning Installations in Data CentresFilter surface / status Anfangsdruckverlust „Clean filter“, "sauber" pressure dropEnddruckverlust „Dirty filter“, "schmutzig" pressure drop1 FiltermatteG4ZigZagFilterG4ZigZagFilterHPG480..85Pa2160..200Pa65..70Pa130..150Pa35..45Pa70..100Pa1„from a clean filter to a dirty filter“:Reduction of airflow at same fan power consumption . Too less airflow may lead to „hot spots“ in the room ! Intelligent filtermanagement will avoid this.2„from a small filter surface to a large filter surface“:Reduction of fan power consumption at same airflow!May 2009Best Practice - Data Centre Cooling65New Design Trends for Air Conditioning Installations in Data CentresFilter surface / status Filter Control Management What does it mean?•Intelligent airflow control in case of dirty filter =>the fan speed will be adapted according to the actual filter pressure drop•A required filter change will automatically be indicatedBenefits:+ Protection against low airflow and hot spots + The airflow across the unit is constant at any time + Longer lifetime of the filter May 2009Best Practice - Data Centre Cooling66New Design Trends for Air Conditioning Installations in Data Centres2. The CRAC-unit:• Fan technology • Part load behaviour • Standby-unit operation • Filter surface / status • Heat exchanger surface <= • Unit dimensions <= • Return air temperature • Return air humidity • Water temperatures • Type of expansion valve • Refrigerant / refrigerant charge • Installed optionsMay 2009Best Practice - Data Centre Cooling67New Design Trends for Air Conditioning Installations in Data CentresUnit dimensions / Heat exchanger surfaceStandard ASD 612 A Footprint: Cooling capacity: tot abs power: Noise level: COP: 51,0kW EER:LowNoise/Energy ALD 612 A1,91 m² 61,3 kW 12,6 + 4,5 kW 60,4 dBA 4,87 3,58Footprint: Cooling capacity: tot abs power : Noise level: COP: EER: May 2009Footprint: Cooling capacity: tot abs power : Noise level: COP: EER:+ 0,36 m² +2,0 kW - 1,9 kW - 5,7 dBA + 0,23 + 0,53Best Practice - Data Centre Cooling2,27 m² 63,3 kW 12,4 + 2,8 kW 54,7 dBA 5,10 4,11=> savings: 2.163 €/year @ 0,13 €/kWh 68New Design Trends for Air Conditioning Installations in Data Centres2. The CRAC-unit:• Fan technology • Part load behaviour • Standby-unit operation • Filter surface / status • Heat exchanger surface • Unit dimensions • Return air temperature <= • Return air humidity <= • Water temperatures • Type of expansion valve • Refrigerant / refrigerant charge • Installed optionsMay 2009Best Practice - Data Centre Cooling69New Design Trends for Air Conditioning Installations in Data CentresInfluence of the return air conditions The leading and most important temperature is the air entering the IT equipment (server). According to the new ASHRAE environmental envelope supply air temperatures up to 27°C are possible. That would lead to return air temperatures of approx. 37°C.35°C 35°8K27°C 27°May 2009Please note: A low return air set-point does not „cure“ problems with heat load. It is the other way around: The lower the return air setpoint the lower the usable cooling capacity of the unit. Furthermore the operating costs are increasing.High return air temperatures and lower return air humidity do not change the content of water in the room. The risk of ESD is as low. Best Practice - Data Centre Cooling70New Design Trends for Air Conditioning Installations in Data CentresInfluence of the return air conditions Advantages of high return air temperatures: (1) CW-units: High return air temperatures are leading towards higher water temperatures. The starting temperature of the free-cooling is much higher. (2) CW-units: To get the same cooling capacity with high return air temperatures and high water temperatures the airflow of the unit can be reduced. Lower airflow leads to lower fan power consumption and a lower noise level. (3) DX-units: Higher return air temperatures are leading towards higher evaporating pressure. With constant condensing pressure the delta between evaporating and condensation pressure is reduced. The compressor power consumption is decreasing. Furthermore the fan speed also can be reduced. But please be aware that too high evaporating pressure can damage the compressor. May 2009Best Practice - Data Centre Cooling71New Design Trends for Air Conditioning Installations in Data CentresThank you for you attention !May 2009Best Practice - Data Centre Cooling72