The most important maintenance task to ensure the efficiency of your air conditioner is to routinely replace or clean your filters. Dirty, clogged filters reduce the amount of air flow and significantly reduce system efficiency. Look for the minimum filter efficiency reporting value, or MERV, which ranges from 1 to 12 for domestic air conditioning units; the higher the number, the better the filtration (and the more energy it will take to extract air through it, so balance air quality concerns with energy costs). Ducts can lose up to 30 percent of airflow due to leaks, and window air conditioning units are notoriously difficult to seal properly.
To find leaks, use the old “smoke trick”. The air compressor and condenser in a central air conditioning system are usually located outside the house, near the foundation. It works best when there's around 24 inches of free space in all directions, so get rid of nearby shrubs, tall grass, leaves, and hanging branches. Federal laws require air conditioning units to be much more efficient than they were just 10 years ago.
For central air conditioning, look for the seasonal energy efficiency ratio, or SEER; for window units, the measurement is simply called the energy efficiency ratio, or EER. The standards require a SEER of 13 and an EER of 8, but devices with higher numbers will cost less to operate. Maintaining your air conditioner is important for energy efficiency, comfort, overall occupant health, and the overall operation of the unit, says Dr. Kirby, leader of the state's Consumer Family Science program and professor at North Carolina State University.
Dr. Kirby also states that a properly functioning air conditioner removes excess moisture from the air and keeps occupants comfortable. Dirty air conditioners or poorly functioning systems can cause microorganisms such as mold to grow, which can aggravate allergies and asthma. If the bleach solution drains easily, skip the next step.
If not, move on to Cleaning the Evaporator Drain. Replace the evaporator coil cover and, if necessary, use aluminum adhesive tape to re-seal it. Warm, humid air from inside your home passes through the evaporator coil inside. The cold coil absorbs heat from the air and cools it before the air is recirculated to your home.
Moisture from the air condenses on the cold surface of the evaporator coil in the form of liquid water, which drips onto a tray below. From the tray, water flows into a drain pipe that normally goes to the basement, floor drain, sink, or outside. Over time, algae and mold can build up and potentially clog the drain, so if the drain doesn't flow or flows very slowly, it will need to be unplugged. A clogged drain can cause damage when the floor is flooded or cause the system to stop cooling to prevent flooding if it is equipped with a drain float.
First look for the drain line where it exits the evaporator coil cabinet. The drain is usually a 1-inch PVC pipe (white, gray or black). Follow it to the end where it drains. Often it drains to outside near condensing unit but can also flow into utility sink or basement drain or into an outside wall in case of attic units.
Hold a rag around space between vacuum hose and drain. The filter in your air conditioning system should be changed at least twice a year - once just before heating season begins and once before cooling season begins - but if you live in particularly dusty area you may want to change it more often. Always replace filter with new one that has same air flow. Moody warns to be careful with “air purifying” or HEPA filters as they can dramatically reduce airflow in your system which can cause inner coil to freeze due to reduced airflow.
While these steps will help keep your air conditioning system in good condition keep in mind that there are items of maintenance that only trained HVAC technician will be able to perform - for example slow refrigerant leak in your air conditioning system can cause costly compressor failure but homeowner doesn't have tools or skills needed to check refrigerant levels. In addition clean ducts and adequate airflow are essential for well-functioning system but homeowners lack equipment needed for job. The final result? While an expert owner can perform some air conditioner maintenance tasks it is necessary to have system checked regularly by expert technician - Kirby suggests service in spring before cooling season and again in fall before heating season. We asked Richard Trethewey - plumbing and heating expert at This Old House - to share his air conditioning maintenance tips for central air and window units: Closing too many interior doors causes central air conditioning systems to become unbalanced meaning there is less airflow throughout house; regular cleaning and maintenance will save you money and extend life of your heat pump or air conditioning unit; remove old filter and install new one matching airflow direction arrows from filter to arrows on unit; dirty filters reduce efficiency of air conditioner so install new one every month during cooling season in central and window units (or clean them if you have washable type); consider running air conditioner along with floor or ceiling fans to circulate cooled air more effectively; due dangers of working near electricity and moving parts of air conditioner it is essential to completely disconnect power to unit; rake up any leaves and debris left outside condenser.