ENERGY IMPLICATIONS OF HVAC FILTERS: DATA ANALYSIS FROM A MONITORED SYSTEM

The resistance to airflow of air filters for removing particulate matter causes energy implications and consequently the operating cost of heating, ventilating and air-conditioning (HVAC) systems. The objective of this dissertation is to determine the energy implications of air cleaning devices installed in the air handling unit (AHU) of a large classroom at Politecnico di Torino, with particular attention to the several sets of fine-filters used from 2010 to 2018. It was concluded that with the aging of the fine-filter is generated a decrease in the fan electric power draw (since the system is at constant volume, CAV), bringing with it possible energy savings. On the other hand, two constraints in selecting air filters were taken into consideration minimum ventilation rate prescribed by ventilation standards and guidelines, and minimum particle removal efficiency. In our investigation, the former shows a very wide range, in fact, the classroom has never reached unhealthy levels of ventilation rate. The filters installed in the AHU did not diminish their efficiency during their service life. Those filters were manufactured with media not electrostatically charged and their removal efficiency did not decrease during their lifetime. Special attention was paid to some specific points, taking into account the uncertainty of the measured data, as well as the normalization of the pressure drop caused by air filters, as detailed is some standardized procedures. Finally, the optimal replacement time was calculated by minimizing the life cycle cost of the filter, obtaining different results depending on the type of filter being examined. The bank of pre-filters installed in the return duct gets clogged faster than the fine-filters one because they tend to capture larger particles. Therefore, the effects of maintenance of the pre-filters were studied and we can conclude that they need to be changed much more often than fine-filters to maintain the classroom pressurized.