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the performance of processing speed and this is one of the major functions of a DC , so , protection of the investment and optimal operating conditions are the priority while also striving for best efficiency ,” says Andrew Koeslag , managing director at AIAC Airconditioning SA .
CONSIDERATIONS FOR DATA CENTRE DESIGNS When it comes to data centres , there are generally three primary points of guidance being :
• The Tier Topology that has been developed by the Uptime Institute .
• Power usage effectiveness – or PUE which has become the primary metric that is used for measuring the effectiveness of overall energy consumption in data centres .
• For cooling , the recommendations according to the American Society of Heating , Refrigerating and Air- Conditioning Engineers ’ ( ASHRAE ) Technical Committee 9.9 - Mission Critical Facilities , Data Centres , Technology Spaces and Electronic Equipment . Ranges from a class A1 to class A4 .
These three points are typically the starting position for any facility and subsequent design criteria that will follow based on the kilowatts of IT componentry to be cooled or cooling per square meter , utility load , whether the facility is going to be a new development , revamp or building retrofit , facility density and rack population rate , maximum load at capacity , air flow design , and also importantly available capital of the client .
It is also recommended , depending on the tier rating , that DCs are also designed and built incorporating two electricity grids for example one from the city where the data centre is located as well as a direct connection with Eskom . These facilities , and according to the Uptime Institute tier , will be designed with reference to N , N + 1 or 2N .
This refers primarily to the redundant capacity where you would see in an N + 1 installation with a capacity of 100kW , 3 x 50kW cooling systems – 2 x operating to meet the 100kW cooling need and 1 x standby in case of any failure . 2N installations have duplication of the entire site and components including the building management system , generators , battery backup , entire cooling system , and so on . For bigger players in the DC space , you also find that the entire 2N centre could be duplicated at an alternate site location – depending on the nature of the data stored of course .
An example of a contained rack with raised floor configuration , allowing cool air to be pushed through from the floor and circulated upwards .
COOLING CONFIGURATIONS AND DESIGN FACTORS “ IT density and power per rack are some of the minimum factors to ensure adequate cooling in a DC . As an industry design default COP of 2.5 is best practice . For the calculation of 1 x kW of power per Kw of IT , this equates to 0.4 kW of cooling required for an average system today . The reality is most data centres ’ cooling is designed for full capacity and redundancy , with no design diversity for capacity , and in the absence of cooling storage or free cooling , you get overdesigned infrastructure with a COP closer to 1.3 . From small to large sized DCs and with over 22 years in building these facilities and looking at best practices – given the various available solutions in cooling – the ever-increasing appetite for saving energy requires inclusion of some element of free cooling through direct or indirect adiabatic cooling or hybrid models with inclusion of naturally cool fresh air into the DC during cooler periods of the year ,” says Raymond Glaus , solutions architect at Dimension Data .
If you look at any DC environment , temperature and humidity control must be very precise . Most of the equipment manufacturers to the sector offer closed control technology that already comes with some type of air filtration for dust and particle control and humidity and dew point control , however , because of the fact that you will also need to comply with the legislation of the country you are operating in , you need to consider the need
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RACA Journal I January 2021 www . hvacronline . co . za