Too Much Air Conditioning? Is There Such A Thing??

By David Kendall david@pullenac.com

What do you know about the capacity of your air conditioning system? Most homeowners have a basic understanding of the size of equipment, and know that AC’s are notated for capacity in terms of tons. One ton equals 12,000 British Thermal Units (BTU’s or Btu’s); therefore, a three ton system has 36,000 BTU’s. Specifically, one ton is the amount of cooling power needed to freeze one ton of water into ice in 24 hours, and a larger system will obviously cool faster than a smaller one.

Many would interpret this to mean that having an AC with more capacity would be preferable since it cools more quickly, but this is not the case. Obviously, we do want to size equipment so that it can adequately lower the temperature even in the hottest part of summer, but we have to be careful about overdoing it especially in a humid environment such as New Orleans. The primary function of an air conditioning system is to cool your home by removing heat, but the secondary function of humidity removal is equally important. Any time your AC is running it is not only making the air colder, it is also removing moisture. This occurs because hot air has more capacity to hold water than cold air, so as we drop the ambient air temperature we also reduce its ability to retain moisture. As the warm, moist air passes through the return duct and travels over the cold evaporator, the moisture condenses on the coil, and drains out of the house. It is then drained through the condensation line to the outside.

An air conditioner is able to remove heat faster than it can reduce humidity, meaning that the run time of your system is critically important. Dryer air is more comfortable than humid air, so an ambient temperature of 78 degrees at 50 percent humidity feels much better than it does if the humidity is significantly higher. Since your system takes longer to dehumidify than it does to cool, it is crucial that your system be sized so as not to cool too quickly and leave you with a damp environment. Everyone knows that excessive humidity causes discomfort, but it also has other undesirable qualities as well. A humid house is a perfect place for mold growth, and by now, we are well aware of the potentially harmful effects of mold on health as well as structural damage to your home. By designing systems that can achieve humidity levels in the range of 50 percent or lower, we significantly reduce the ability of mold to grow and propagate.

In the past, air conditioners were restricted to a specific capacity, so if you had a three-ton system, it would always operate at that level when the system was activated regardless of the temperature. This might be perfect at 100 degrees, but if the temperature is lower it means that your system would be oversized and the run time would be insufficient for adequate dehumidification. Some studies have shown that the typical air conditioning system is too large as much as 75 percent of the time. With the advent of dual-stage equipment, this is no longer the case. You can now purchase systems that operate at a low as well as a high speed, meaning that this type of AC will make your home dryer and more comfortable. Not only will two-stage equipment make you feel better and contribute to a healthier environment, it can also save you money by reducing your electricity bills since less energy is required at lower capacities.

Trane has several models capable of dual-stage operation. This equipment is ideally suited for the conditions we have in the Gulf Coast region. For more information, check out this link to Trane’s ultimate, two-speed system. Please feel free to call us for an in-home consultation to discuss your particular needs.