The Biggest AC Misconception that Leads to Sticky Situations

Are you feeling sticky in your house even though your AC is running frequently to keep up with the heat? Is your unit old and in need of replacing? If you are considering buying a new HVAC system, read this first!


During our Whole Home Diagnostic Testing, we often find HVAC systems that are much too big for the houses they serve. It may sound like a good idea at the time to buy a bigger system - bigger system, more power to cool a house, right? Although this sounds correct in theory, many people misunderstand a very important detail. The problem isn't the ability to cool, but the ability to dehumidify. Bigger systems will end up dehumidifying less, leaving you in a sticky situation.

AC units dehumidify by means of condensation. When air passes over the cooling coils within an AC, water condenses out of the air. The same physics happens when hot air comes in contact with a cold soda can. The air that condenses in the system runs down the cooling coils and drains to the outdoors.

If your AC is a single-stage system (most standard units are), it will run at full power, blowing lots of cold air until the air temperature at the thermostat reaches the set point. If a system has more capacity than what is needed to meet the load (i.e., the system is too big for the house), it will cool the air with a very short run cycle but won’t run long enough to dehumidify, a phenomena known as “short-cycling.” This leads to cold, moist air entering the space.

In addition to high indoor humidity, short cycling creates excessive heat build up from the compressor and fan turning on frequently. This adds wear and tear and shortens the lifespan of the system. It is very, and I repeat, very important to properly size an HVAC system with a Manual J calculation. Every home has different needs due to construction, window placement and selection, orientation, preferred set points, etc, so every system needs to be properly sized.

By properly sizing your system, you help ensure temperature and humidity control within your home. You may even save money through the purchase of a smaller (properly sized) system and lower heating and cooling costs.

E3 offers HVAC sizing services to help you find the perfect sized system. Contact us today to learn more about our services 

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