Arkansas HVACR NewsMagazine September 2019

S tate, National, Chapter News Tech News

find a value of 320 to 360 fpm. For a 3.5 ton, the numbers run at just under 500 fpm and 5 ton, just under 700 fpm. These numbers exceed practical flows by a factor of two to three times, taxing filter effectiveness and pressures (static) within the duct system. The result is ineffective filtering with excessive noise, energy use and the potential for short equipment life. History- First of all, widespread use of residential air conditioning is not that old. The 1970’s brought central HVAC to production builders. This leaves the industry a little less than 50 years old. Those first air handlers and furnaces used wire loops, baskets and cages to hold filter media in place. These type products made filter changes a difficult task for home owners. The results were filters did not get changed regularly and evaporators were cleaned periodically. Older evaporators were more accessible at that time and fin per inch count (density) was such that a light shined through the evaporator revealed whether or not the evaporator was dirty or clean. In some instances chemicals were sprayed onto the surface of the evaporator. These chemicals would loosen the dirt on the aluminum fins and a foaming action would push debris out of the spaces between the fins. The first attempt to provide a practical solution came when a company realized filter access shortcomings and devised a

filter frame to fit beneath an up-flow furnace or air handler. This frame, when installed with new or existing equipment allowed a homeowner to change the filter in 10 seconds and leave the furnace or air handler access undisturbed. The product was very popular and gained market share quickly. As energy efficiency gained greater importance, manufacturers found adding more mass (copper and aluminum) to evaporators gave betters performance numbers. So gradually the evaporators became denser, air flow more restrictive and filtering more important. Today’s evaporators have more fins per inch and the fins are pleated or waved for more surface area. This fact emphasizes the importance of providing protection for the evaporator with proper filtering because new evaporators can no longer be cleaned in place. Solutions- The lack of available product information has been an issue for years. Filter manufacturers are reluctant to publish data on filter performance due to complexity of the issue and the confusion the data can provide. Just as there are many formulas to obtain a particular conclusion to a mathematical equation, there are ways to test filter designs and justify their use. Two filters may look identical from a consumer’s standpoint however the particulate size the filter stops and the