Dehumidifiers are designed to pull water from air and so do air conditioners. The big difference is air conditioners have two functions, lowering the temperature and removing humidity. The temperature control has priority. The dehumidifier concentrates on removing humidity only.
Both units function the same way circulating refrigerant through a continuous loop, and converting the refrigerant between a gas and liquid. In the gas state the refrigerant absorbs heat via cooling coils and as the air cools it releases water vapor which is drained away; the resultant air is now dry.
A major difference between the ac unit and the dehumidifier is that the ac unit converts the gas back into a liquid producing heat outside the home, but the humidifier converts back inside the home. This is why the ac unit cools the home and the humidifier does not.
So why is a humidifier needed in humid climates? Most ac units are incorrectly sized for the home, almost all are oversized because they are not sized using heating and cooling load calculations; it’s usually done by rule of thumb.
Units that are oversized cool the air quickly and short cycle. Short cycling doesn’t provide enough time for the dehumidification process to work, so the humidity stays in the air and becomes cold and clammy. However, if the unit is sized correctly it would run for longer periods and remove the moisture. If sized correctly a smaller unit would cost less to buy and run, and would last a lot longer as short cycling wears out the mechanical parts sooner.
Bottom line, install the right size HVAC system that has been designed using the ACCA manual J and S calculations and you won’t need a dehumidifier.
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