LG Duct UVnano Filter Box

The arrival of COVID-19 and its impact on our lives has stressed the importance of air quality. The trend to improve indoor environments not only relates to comfort and convenience but also takes indoor air quality into consideration. Air quality is measured by the concentration of pollutants in the air such as gases, dust particles and microbes. According to ASHRAE 62.1, if the concentration of these pollutants in a space exceeds a certain level, the air quality is considered poor and may negatively affect the occupants. Thus, solutions to control these concentrations are essential.  

LG provides various solutions for air quality control from stand-alone air purifiers to air purification kits for VRF and single/multi split cassette-type indoor units (except the 2-way cassette).   

The UVnano Filter Box is a new option for Mid Static Duct units (M1, M2, M3 Chassis) that is installed at the return air side of the unit and aims to clean indoor air and improve air quality. The new UVnano Filter Box is expected to be launched globally by October of this year. The features of the new UVnano Filter Box will be introduced in this article.

The filter box consists of three main components; pre-filter, UVnano (UVC LED), and MERV 13 filter (ePM1 50% filter). There are 2 of each component and they are accessible either from the side or the bottom of the unit.

In order to verify the performance of UVC LED, two types of tests were carried out. The first one was to verify bacteria sterilization performance, and the other one was to verify sterilization of viruses parasitizing on bacteria. The tests are conducted in accordance with TUV Rheinland Standard.   
 
In the first test, three types of bacteria were cultured on 6 membranes. They were, then, fixed on the pre-filter as a setup for the test. After that, the UVC LEDs were implemented as shown in the table below: 

The TUV verification report shows that the UVC LED has a 99.99% sterilization performance on each type of cultured bacteria at the measuring points. This result would be different in practical usage conditions of an air conditioning system considering the airflow rate and other factors.

Similarly, in the second test, a virus was prepared and the host bacteria were cultured. 6 samples were prepared and attached to the pre-filter and the UVC LEDs were implemented in the same way as in the previous test. The test was conducted three times to confirm the results. And the results at each measuring point for the three test runs showed a virus sterilization performance of 99.99% as the TUV Rheinland report shows.  

According to ASHRAE recommendations, the risk of infection per high filter grade can be improved slightly by increasing the ventilation rate. And with MERV 13, Bacteria and smoke can be removed, in addition to PM1 at an efficiency of at least 50%. Test results for filters’ ability to reduce infection risks with proper ventilation rates show that MERV 13’s risk of infection rate at no ventilation is slightly higher than that of HEPA filters. However, with ventilation rates at more than once per hour, this small gap can be covered.

With improved filtration (MERV 13 or higher), increasing ventilation provides a negligible contribution to the removal of bioaerosols from indoor air. Therefore, designing for high filtration and ventilating based on ASHRAE 62.1 is recommended to save energy and operating costs.

Note: MERV 13 filters cause a pressure drop that can be compensated for by adjusting the E.S.P value of the duct unit. For further details, please refer to the PDB and standard proposal.

MERV 13 filters have a more than 90% trapping efficiency when viruses spread in droplet form. Usually, normal activities such as coughing, speaking and even just breathing release droplets that vary in size from less than 1μm up to 10μm. Viruses on their own are very small in size, but they stick easily to these droplets which, in turn, are captured efficiently by MERV 13 filters.