Feature for people to go into , and do various maintenance within the white space , even if it ’ s only for a few minutes in a week .
You need to thus ensure that all the necessary building regulations are complied with that includes introduction of an amount of fresh air into the space . This requirement will determine the filtration system you want to put into place so that you are not just taking outside air into the space because any particulate matter may cause a number of instances of damage to the components . This function is typically managed through the design of the air handling unit ( s ) ( AHU ).
“ Part of the ASHRAE TC 9.9 recommendations are classes A1 to A4 . These are a temperature and humidity range to design your cooling system according to . Class A1 will be ranges between 18C and 27C , while the relative humidity can vary between 20 % and 80 %. These ranges apply to any type of data centre . The two most popular types of cooling systems currently are direct expansion ( DX ) and chilled water ( CW ). Further you can also add cooling towers – depending on the location and evaporative cooling to the list of solutions for DCs ,” says Olu Soluade , managing director at AOS Consulting Engineers .
In most cases the cooling configuration and systems will be drawn from three of the considerations mentioned above , these being :
• the type of project ( new / revamp / retrofit )/ location
• the required Tier level or rating
• the IT / cooling capacity required
Data centre development has boomed due to the increased demand for digital services .
opting for a chiller system is just going to be too costly for the client proportionately , but anything above 500kW , a CW system is the better solution because of the flexibility it allows and in adding more capacity at a later stage . The detriment on CW systems is the initial capital cost compared to DX , so if the client has a tight budget the design and choice of cooling can accommodate .
The reason these particular aspects are usually the starting point is due to the fact that with a new development you could pretty much have a blank canvas to work and design according to , while a building revamp or retrofit may limit the design parameters – for example a raised floor may be impossible to install . The Tier of the DC also depends on the redundancy requirements . The kilowatts ( kW ) in cooling required coupled with redundancy then determines the size and choice of cooling system .
“ There are also many configurations that revolve around the IT rack itself , these are your down blow or under floor cooling configurations , in-rack cooling or pod type and you also get a flooding solution which means you flood the entire data centre / hall with serviced air . Flooding is more common in hyperscale , or very large-scale applications . You will also find rear-door coupling configurations which provides minimum impact with respects to footprint . In the past the tight humidity range had a lot to do with tape drives and other legacy equipment with its associated issues in relation to humidity , but as you can see from the allowable ranges in humidity today this is much less of a factor ,” adds Mikhail Poonsamy , sales engineer at AIAC Airconditioning SA .
Although each installation has its own different parameters , generally if you take the load of any space that is up to 500kW ,
www . hvacronline . co . za RACA Journal I January 2021 35