Improving Your AC Efficiency with These Simple Tasks

For the next 4 or 5 months, air conditioners will run at regular intervals to make homes safe and comfortable. On most days, the system will function adequately. But there will be days of extreme heat and humidity that might lead one to wish that the air conditioner cooling output was a little better or a little faster. If the system is well-maintained and performing as designed, there might be human actions that impact the function of the air conditioner system. Consider these actions.

AC Efficiency: Understanding Air Volume

Air conditioning requires massive amounts of air movement, both inside and outside. For this discussion, we will only consider the air movement inside.

For every ton of air conditioning, a blower motor must move 400 cubic feet per minute (CFM); a three-ton unit will need to move 1200 CFM. That means that every two minutes, statistically, the entire volume of a 2400-square-foot home will move through the evaporator chamber and come into contact with cold coils before returning to the home. Anything that slows or blocks the free movement of air hinders the cooling process.

AC Efficiency: Potential Hindrances of Air Movement

• Air Filters. The air moves rapidly through an air filter, usually less than 2’ square. Dust and airborne pollutants collect on the filter and after a few months, the collection will begin to slow air movement. The filter should be changed at least every three months.
• Return Vents. Each story of a home should have at least one return vent installed about 6 feet up on the wall. The blower motor pulls hot air from the home through these vents and directly into the cooling process. Of course, if anything blocks these vents, it will severely restrict air movement. Keep drapes and wall hangings 6 to 12 inches away from these vents.
• Supply vents. The blower motor delivers cool air to the home via floor or low-wall-mounted supply vents. If furniture, rugs, or clothes cover a supply vent, not only does it prevent cool air from entering the space, but the static air pressure in the vents increases. That allows cool air to find even the smallest flaw in the ductwork, pushing the valuable cooled air outdoors. Keep obstacles at least 6 to 12 inches away from supply vents.

AC Efficiency: The Duct Network

A system of ducts carries a massive volume of air from the home to the evaporator chamber and back to the home.

• The air moving through the ductwork is under pressure. Air will be pushed out of any leak or opening in the network, usually into the attic, garage, or crawlspace under the home.
• Any ductwork installed in unconditioned space should be insulated to prevent the air inside from heating.
• Even insulated ducts that carry air to the far reaches of a home will gain heat on its journey.
• Dust and particles will eventually collect inside the ducts. They should be cleaned as needed; a healthy recommendation is every 3 to 5 years.

AC Efficiency: Battling Heat

The ductwork is the first place where the cool air can encounter heat and lose its effectiveness.

• The insulation in a home is designed to SLOW the transfer of heat—from outside to inside in the summer and inside to outside in the winter. On a cool day, stick your head into the attic and check the depth of insulation. It should be at least 12 inches deep.
• Openings around doors and windows can also develop gaps, allowing air to be forced out with each cooling cycle. Caulking will fill the gaps and prevent air from flowing out the window.
• Close window treatments during the heat of the day on the south and west sides of the house. Solar gain can increase indoor temperatures by as much as 10 degrees.
• Don’t add to the problem if you can help it. Use heat-producing appliances less and later in the day when outdoor temperatures have dropped.

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For more information about R.M. Mullinix and ways to improve your AC efficiency, schedule an appointment or visit our HVAC maintenance information page.