Advice from Contractors:

Get Ready to Chill This Summer

By Rick Dole

Don't wait until the first 90-degree day of the year to check your air conditioning system. You'll already be miserable, and HVAC professionals will be very busy. Now is the time to do some maintenance or consider a new unit, if needed.

Air Conditioning 101

An air conditioner cools an area by transferring the heat to a less objectionable place, usually outside. The unique elements that make the air conditioning system work are the compressor, the refrigerant gas, and the expansion valve. When refrigerant is compressed into a hot liquid and forced through a tiny hole in the expansion valve, it changes (flashes) into a very cold gas. It is then able to cool the room by absorbing heat.

With central air conditioning, the condenser unit that sits on a cement pad outside of your house contains the compressor, the condenser coil, and evaporator coil, as well as the electrical connections and controls. The condenser and evaporator coils are heat exchangers (similar to car radiators). The small copper line going into the house is the high-pressure line to the expansion valve. The larger suction side copper line next to it flows to the intake (suction) side of the compressor.

General Maintenance

The blower fan filter on a central air system should be changed at least once a year, and that is a good time to check the condensation drain as well. It's also important to keep leaves and other debris away from the condenser coil. The condenser unit can be opened for better access to the condenser coil, but always shut off the power first.

The evaporator coil is often inaccessible, but the filter can be changed. If you are lucky and have access, check to make sure the airflow through the coil is not restricted by a buildup of lint and dirt. Compressed air is best when cleaning coils, but a soft brush and vacuum also will work. Be very careful not to mash the fins, or the coil will lose efficiency.

Safety Tips

• Keep away from moving parts.
• Keep away from electrical connections.
• Shut off the power before cleaning the coils or performing any work on the system.
• Use eye protection when cleaning the coils.

When to Call in the Pros

A properly installed air conditioning system will last many years, but it may occasionally have trouble. Handy do-it-yourselfers can do some troubleshooting, but if you are inexperienced, it is easy to short out a compressor—and very expensive to replace it. A good source of available local professionals is ImproveNet, which conducts independent screening of the professionals in its network. (Editor's note: Visit our Find a Contractor page to use this free service.)

If your unit is not cooling properly, it means there is not enough of a heat exchange in the condenser coil. This is usually because of obstructed airflow through the coil, or because the condenser fan doesn't work. Another cause could be a shortage of refrigerant because of a leak in the system. If you've checked that airflow across the coil is not hampered with leaves and other debris, call a professional before going any further on your own.

Finally, if you plan to replace or install a new air conditioner any bigger than a window unit, you need to contact a qualified air conditioning contractor. Installation requires special equipment and, in many areas, a license to work with refrigerant. If the installation is done improperly, the compressor will have a very short life.

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