Arkansas HVACR NewsMagazine April 2018

S tate, National, Chapter News Tech News

his doors open! I don’t want them calling me up in the middle of August complaining that the house is too warm.” What was evolving seemed to be a fight between my old man and the customer, although the customer did not even know that battle lines have been drawn. My father was a very intelligent man and I was thoroughly confused with the ease with which he threw all common sense and system design knowledge out the double pane, low emissivity, window. Even properly sized systems are, for the most part, oversized. In Long Island, New York, where we lived at the time, we typically design our air conditioning systems to operate at an 85°F outside ambient temperature. What happens when the outside temperature is lower than 85°F? Well, the heat gain of the structure decreases and the capacity of the air conditioning equipment increases. So, our air conditioning system has the ability to provide more cooling when our house actually needs less. If we size our air conditioning equipment using industry accepted guidelines, we should be able to use the results of these calculations to size our equipment. What many contractors do is use the results of their

calculations as a guideline. If the calculated results indicate that a three-ton air conditioning system is needed, a four-ton system is often installed. Why? “We want to make certain that we did it right… Besides, we don’t want the customer calling us up in the middle of August complaining that the house is too warm, do we?” In the real world, we simply cannot continue to size air conditioning equipment for the one or two days in the summer that put a real strain on the equipment. We need to be confident with the results of our calculations. If we aren’t, why calculate in the first place? So, what are the effects of oversized air conditioning equipment? Where do we start? Let’s take a look: • Larger air conditioning equipment costs the customer more to purchase • Larger air conditioning equipment moves more air, so a larger air distribution system is required. This, by the way, also costs more money • The installation costs are higher because of larger field- installed refrigerant lines, larger pads, larger ductwork, etc.