Malpractices of application of air filters
(1) Use metal mesh filter for Fan Coil Unit
Metal mesh air filter is commonly used as an air filtration device for fan coil
unit (FCU) in Hong Kong. Is it the only choice that we can take? As shown in the graphs below, metal mesh filter has very low filtration efficiency (>27%) for particulates of PM5 or below. It just achieves a MERV 2-3 rating according to ASHRAE Std 52.2. According to application guidelines of
NAFA (National Air Filtration Association), air filter of MERV 5-8 is recommended for FCU in order that the cooling coil is adequately protected against fouling to avoid decrease in thermal transfer efficiency and biological contamination.
Meanwhile, research revealed that fouled cooling coil could lead to colonization of various species of fungi/bacteria that could spread to the building occupants and cause allergies and diseases.
In an office space, the dominating sizes of particulate matters are 3μm and below given no irregular activities other than normal office activities are undertaken. Metal mesh filter installing on FCU therefore does not protect the FCU itself nor improve the IAQ (Indoor Air Quality).
Fine dust and organic substances
passing through metal mesh filter will get into cooling coils and fins; trapped and deposited therein. An increase in coil fouling material thickness could lead to an increase in thermal resistance between cooling coil and the airstream and consequently, decreasing the coil overall heat transfer coefficient.
In addition to performance degradation of FCU, it could give rise to narrowing of Delta T of chilled water system and in turn degradation of Coefficient of Performance (COP) of the MVAC system.
Nanofil Filtration Technology Ltd. has developed different types of fan coil filter with their patented nanofibrous filter media that achieves a high filtration efficiency (>65% for PM2.5 and above) and low pressure drop. It also has a high antibacterial (99.99%, SGS) and antiviral (COVID-19 Omicron Variant virus – over 99%, VRS* (UK)) efficacy.
It can bring the following benefits to the building owners and occupants.
2.Reduce risk of spread of viruses/fungi/bacteria
3.Reduce fouling and cleaning cost of cooling coil
4.Improve COP of MVAC system
* Virology Research Services Ltd. (UK)
Challenge the status quo!
Call us if you want to save energy, reduce maintenance cost and improve IAQ.
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