Arkansas HVACR NewsMagazine March 2019

S tate, National, Chapter News Tech News

perform with only one high efficiency air filter. Some systems require commercial grade returns grills to obtain flows while others (platform return) may need extensive alteration. Supply plenum design criteria- Substantial gains in air flow performance and comfort can be achieved with simple changes in plenum design. These include increased plenum length to accommodate air stabilization off the blower, a pressure rebound zone and adequate take off surface. We must also include more efficient transitions when installing evaporators or adapting existing plenums and duct work. The study found unexpected gains by avoiding taps at specific areas of the plenum formerly utilized without hesitation. Duct design and proper installation- Duct flows and their performance have been over rated for quite some time. New duct performance flow criteria are available through a few sources. Even more important than equipment selection is the fact actual duct installation quality will determine performance outcomes. We must pay attention to air duct installation. Terminal device use- Very little attention is paid to grill location and the type grill used. Contractors found same size grills with

differing flowing upward of 20 percent more air. Some homes could be fixed with grill replacement. With homes located in hot and humid climate it is extremely important to avoid air delivery to exterior wall at velocities above fifty feet per minute. During mild weather the practice can cause condensation and deterioration of construction material. In the U.S. the over arching goal has been to weatherize the structure by sealing the envelope and adding insulation. With less than fifteen percent of homes without a central air conditioning system the need to adopt a change becomes more apparent. Our industry must look to provide sustainability through a process of fixing the air delivery system, and sealing the envelope and finally adding insulation. Fixing the air delivery system later only calls for additional weatherization measures to be repeated. Consumers will be slow to accept the idea. After all, we put the air conditioning in. There must me an honest effort to advance a “System Performance” approach to inform the home owner so an intelligent decision can be made on possibly their most valuable investment. To conclude, poor system performance in the retrofit market left unaltered, costs everyone. Obviously, it costs the manufacturers