Arkansas HVACR NewsMagazine November 2020

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The second question should be is “What quantity and quality of filtration does this system require?” No system should be installed relying on the filter space at the bottom of an air handler or furnace. These spaces are provided only to keep trash out of the unit during installation. One-inch filters should become extinct in your shop replaced by media filters with thickness of three and a half inches or more. This will require forward thinking and planning. On systems more than 3- ton nominal capacity, two filters at a minimum should be used as a rule.

work as engineers design is by providing effective air delivery. With today’s inverter or variable capacity equipment it would seem velocity has been forgotten. With equipment continually changing capacity and air flow, terminal devices are rendered useless. Duct systems should be designed to maintain velocities 600 and 900 feet per minute. Distribution begins with a properly configured plenum or reduced extended trunk line. Homes with variable capacity equipment other than simple unloading scrolls should always be zoned to take advantage of the technology. This means incorporating remote thermostats and dampers that operate fully open or fully closed. Modulating damper systems that open and close to match the current running capacity completely disregard distribution requirements. Your target for delivered air remains the same as discussed under the prior heading of “Assessing the Issues”. Duct systems should be designed to maintain velocities 600 and 900 feet per minute.

Photo 2: Filter Resistance

The third question should be “Is the air deli very effective?” The HVAC contracting community must remember that air flow within every section of the system is controllable by installation methods. The only way the blower section can

Photo 3: Transitions