Arkansas HVACR NewsMagazine May 2019

S tate, National, Chapter News Tech News

latent loads continue to gather, producing high humidity. There also remains the issue of making sure the system sold has the ability to cool the space installed within. Where performance is concerned, nominal tonnage is a term that needs to be removed from the contractor’s vocabulary. When dealing with today’s equipment, there is a capacity penalty for higher EER. It is imperative a load calculation be performed to minimize the probability of failing to calculate the load on the home. Diligence with respect to Manual S is the contractor’s responsibility in correcting performance of equipment to ensure capacity delivery.Adjusting performance should be researched long before equipment is purchased. Every combination of equipment may have dramatically different profiles on how sensible and latent loads are addressed. When installing inverter driven systems, we need to remember the terminal devices (grille for conversation). The grille is specifically designed to flow between 600-900 fpm. Anything less, and air will not reach intended targets. Anything more and the terminals become noisy and adds resistance to the air delivery. When we allow the indoor section (blowers) to match inverter speeds over the entire duct system, we kill grille performance. There must be a strategy to keep air flow speeds up in the duct to take advantage of effective air delivery. Additionally, when airflow within ducts is low, there is a potential for cold air in the duct to overcome insulation levels and cause condensation (reaching dew point) on

Inverter Driven System Size Matters! Tom Turner When selecting inverter driven systems, the contracting community tends to ignore sizing issues because the popular belief is: The system will run only as necessary — you can’t oversize. Nothing could be further from the truth. Proper sizing remains a fundamental in hot, humid climates. To be sure, inverter systems are here to stay and are valuable at shedding shoulder-month KWh. While the equipment may have ability to enhance humidity control during a normal run cycle with proper thermostat programming, a contractor will fight a losing battle when sizing is ignored. When we think about the issue rationally, the concept becomes clear. The home is a container with specific dimensions and leakage. When we oversize the refrigerant delivery system, we are placing a life sentence on the equipment to continually underperform with respect to humidity removal. To address latent capacity, we must have an evaporator cold enough to wring out moisture without overcooling the space. Oversizing will provide an effectively smaller refrigerant capacity to handle aforementioned specific space and infiltration along with internal latent loads. While the sensible load may remain balanced for a short time, …a contractor will fight a losing battle when sizing is ignored.