Arkansas HVACR NewsMagazine May 2021

HVACR NewsMagazine May 2021

State National Chapter News

Control and Prevention (CDC) is recommending the use of the highest efficiency filters as possible that do not compromise the overall effectiveness of the HVAC system. Filtration is only one aspect of indoor air quality. The four basic factors that influence indoor air quality are: 1. buildings occupants; 2. pollution pathways; 3. other sources of contamination; and 4. the HVAC system. There are many variables within the HVAC system itself, including personal activity levels, uniformity of temperature, humidity, ventilation and air exchange. The HVAC system design and operation are at the heart of indoor air quality control. A properly balanced system isolates and removes contaminates through pressure control, filtration and exhaust. The MERV 13 factor MERV 13 is not the highest-rated filter available, but it is the filter rating that has risen to the forefront as the CDC has recommended the use of high-efficiency filters in response to the pandemic. The MERV scale rates filters from MERV 1- 20. The higher the number, the higher the efficiency over a range of particle sizes. Having a filter that is rated a MERV 13 or higher has a removal efficiency in the 0.30 – 1.0 micron, ranging from 50% to 95%. The bioaerosol particle size range that contains viruses, including corona viruses, is within this typically range. Installing a MERV 10 or less filter – as was typically the case in commercial and residential systems prior to the pandemic – has no effect on particulates in the 0.30 – 1.0-micron size range. There are some complications relating to the installation of MERV 13 filters in systems with 1” and 2” filter racks, as MERV 13 filters are typically deeper to minimize pressure drop. A basic switch to a MERV 13 from a lower-rated filter in a 1” or 2” system presents unintended consequences, which result in a cascade of increases within the

HVAC system. These manifest in higher resistance, increased pressure, as well as increases in energy use in the system. This can cause airflow reductions, freezing of the air conditioner coil and, potentially, damage to the compressor. A workaround could be to retrofit a larger rack to accommodate a deeper filter with significantly more filtration media. This is not a simple or cheap task. Cost is not the only factor though, as a retrofit would also require steps to ensure the enlarged filter rack is as airtight as possible to prevent air bypass or depressurization effects from occurring. High-efficiency filtration operating considerations After higher-rated filters are installed and operating, they should be monitored and maintained to provide maximum filtration, while not overworking the supply fan. Overloading the fan can lead to filter “blow - out” situations, which leads to virtually no air filtration. To help automate this, a differential-pressure measurement device can be installed across the filter bank to identify the appropriate change-out times. Also, pressure drop switches may be used to provide an alarm input to a Building Automation System that alerts operators to change the filter. With the internet of things (IOT), this technology is also becoming more accessible to residential applications. These articles on filtration were provided by Johns Manville and first appeared in their blog dated April 22, 2021. We appreciate their sharing their information to the Arkansas HVACR industry. We recommend that you subscribe to their blog for ongoing information and training. To learn more about Johns Manville HVAC Insulation go to https://www.jm.com/en/hvac/ or to their library at https://www.jm.com/en/hvac/the-source/