Arkansas HVACR NewsMagazine March 2022

HVACR NewsMagazine March 2022

Tech News

or end or the evaporator terminates, this length can be added to the 18” required prior to changing direction. At the end of the plenum, we must employ the use of rebound zone for terminate plenums or a reduced trunk on extended plenums. This keeps velocity up so once the distribution branches take over the air will have enough energy to move through the terminal device (register) effectively. 20” x 20” plenums in lengths of 4’ ( 1.5 tons) to 8’ (5 tons) nomi nal capacity is needed to provide enough surface area for tapping ducts. Properly configured and sized duct for the correct cfm and velocity- Over sizing duct will increase the chance of running out or air and lowering the velocity so air just trickles out the duct and never makes it to targeted ceiling, walls and windows. Under sizing ducts will place pressure against the fan either causing an old fan to slip in the air stream or a variable speed fan to use more energy and become noisy during operation. Correctly placed registers that target the proper placement of air- Terminal device (registers) placement is extremely important. Air flow above 50 feet per minute should never push against a perpendicular (wall) surface. We must utilize the insulation in the ceiling and walls as a buffer against ambient air temperatures. The low energy air during cooling or high energy air during heating, loads the insulation to push back ambient temperatures. It is good to remember high sidewall delivery with sidewall grills are the most efficient method to distribute air. Curved blade

grills that keep the air high against the ceiling is the second preferred method of delivery. Whenever possible abandon perimeter duct systems as they do not deliver air as efficiently or effectively as does the interior to exterior methods. This is particularly true in cooling dominate climates. A system where the refrigerant charge is weighed in- As a last point, nothing saves more time than weighing in a charge on a new installation, whether new construction or replacement. If evacuation procedures are followed and the charge is weighed in, chance are minimal you will have a callback at the address. Most install issues are charge related. By utilizing the process, you can rest assured the charge is correct and not due to an issue of temperature or pressure.

Your job is not an easy one. Poor performance of installed equipment proves the fact time after time. Make your job stand out with duct systems that allow the equipment to deliver air as the manufacturer intended. If you do, you will have more business than you ever believed possible.