Feature
the highest level of filtration as well as additives to control and eliminate even pathogens .
As the globe struggles with outdoor air quality , this has a direct impact on the air that enters buildings and so the traditional solution of introducing fresh air into a space to dilute contaminants is changing quickly as outside air quality deteriorates .
Every unitary air conditioner type uses a particular air filter to clean the air as it passes through the blower unit . Some use rudimentary filters that only catch large particulates all the way through to units that make use of high efficiency particulate arrestor ( HEPA ) filters .
Unitary units are considered more efficient at “ cleaning air ” dependant on their configuration , as air in and blown back out is situated at the same location .
Filters are usually placed on the return air of the unitary system . The air ( that potentially contains contaminants ) is trapped here at the filter . “ Clean air ” is then discharged into the space together with the cooled air .
The sizes of contaminants that exist in general air range from 0.01 microns to 10 000 microns . Virus , oil smoke , fumes and suspended impurities have sizes ranging from 0.01 to 1 micron . Mould , pollen , fog , dust , mists and ashes range from 1 to 100 microns . Dust emitted from heavy industry factories is about 100 to 10 000 microns , as some examples .
The ability of these filters to trap particles is measured by using the industry standard known as MERV or Minimum Efficiency Reporting Value . The values range from 1 to 20 and can trap particle sizes from 0.3 microns to 10 microns . The higher the value , the better the filter is able to trap smaller particles .
Standard office and home applications usually range from 1 to 12 , with MERV 12 being able to trap particles from 1 to 3 microns . Highly specialised applications such as a clean room or a medical doctors facility would use MERV 16 to MERV 20 filters ( where applicable ).
TYPES OF COMMON UNITARY FILTRATION AVAILABLE Plastic mesh filters are the most commonly installed at the return air of most indoor unit of unitary units . They trap larger particulates such as dust and hair . They are also the easiest for users to clean themselves and usually only involve using soapy water . Regular cleaning helps to ensure that the efficiency of the unit and hence energy savings , as well as clean air is continuous . Electrostatic air filter technology is commonly placed in the return air of the unit where the air is subjected to high voltage up to 12kV between two plates . The ionised particles are then drawn to the grounded plates . The electronic circuit used to generate the voltage is usually embedded on the control printed circuit board or a separate module .
Carbon and adhesive filters are further other types available . The carbon type is made of activated carbon that is effective in removing odour causing gases and bacteria . Adhesive type is made of cotton and fibreglass material coated with adhesive oil or liquid which typically traps any particles .
Split or unitary equipment can meet the demands of many applications .
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RACA Journal I November 2022 www . refrigerationandaircon . co . za