If you are interested in why common air conditioning units DO remove moisture from the air, read on. Otherwise, excuse my babble.....please. In the typical window air conditioner, condensate which collects at the bottom of the evaporator coil (the one that feels cool to the touch) is "condensed" from the inside air, which is a mixture of "inside air", air infiltrating through cracks and crevices in the home, and the portion of air which enters through the "fresh air" damper in the unit (but only when it is open). In all units I have seen, the portion of air entering through the "fresh air" damper is probably no more than 20% of the total being circulated by the fan. The condensate (water) collected at the bottom of the evaporator coil flows by gravity to the "outside" part of the unit. Here it is held in a collector pan. The purpose of the collector pan is to allow water to be entrained in the air stream created by the condenser fan and to be blown across the condenser coil (the hot one). This increases the efficiency of the unit by taking advantage of the principle of "latent heat of vaporization". In other words, the moisture laden air stream, is more efficient in removing heat from the condenser coil, when compared to dryer air. Central A/C units have many variants, but the typical system does indeed remove moisture from the air in the same way. However, central units may or may not have a collector pan. The condensate may simply be routed to a drain. If the unit is equipped with a humidifier, the water generally comes from a tap water source. It is simply sprayed in a fine mist into the air stream when the unit is operating. Some systems use a rotating fabric moisture laden wheel (ala DC sort of..) to impart moisture into the air stream. Other variants undoubtedly exist. These systems usually have a set amount of fresh air intake (in the neighborhood of 15% if memory serves...) except for systems installed in warehouses, etc which sometimes have NO fresh air intake. It is not uncommon for a warehouse system in this area to operate at 15% RH in winter and no more than 30% in summer (assuming the warehouse has A/C). This is a simplified explanation of the common A/C units which employ a closed system (i.e. freon, ammonia, etc.) to operate. Open system variants, like "swamp coolers" and other absorption type coolers are not addressed here. So, in general, the common everyday air conditioning system found in the eastern United States DOES remove moisture from the air. The extent of dehumidification (and the lower limit of RH which can be attained) depends on several factors, including refrigerant type and state of charge, mass air flow rate, existing RH in the circulating air, air exchange rate, etc.. This, off the top of my head. I left this stuff behind 10 years ago...... Let's talk about pianos. Tom Robinson East Tennessee
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