How You Can Winterize Your Central Air Conditioning System's Outdoor Unit

With autumn almost here and wintry weather not too far behind it, it is time to start thinking about protecting your central air conditioning system's outside unit. Winterizing the outside unit, which houses the compressor and condenser coils, is an important preventative maintenance step to take. Winterizing will shield the unit from the harsh cold and frozen precipitation, as well as protect the system from other potential damage. Below is more information on how you can winterize your outside unit and what and what not to do:

Disconnect the electrical power

The first step to take whenever you use your air conditioner for the last time before cold weather sets in is to disconnect the power supply. This will prevent undesirable power surges to the unit or accidental start-ups of the unit during low temperatures, which may damage the compressor.

You may not realize that the system's outdoor unit is connected to an individual circuit that can be turned on and off at a local panel. This panel will be located in close proximity to the outdoor unit and is likely mounted on the closest exterior wall to the home. To disconnect power to the unit, open the panel cover and either flip the power switch or remove the pull disconnect by grabbing the handle and pulling firmly, depending on which one is installed. Be careful when performing this step, as many outdoor units are powered by a full 240 volts of electric current.

Cover the top of the unit

The next step in the winterizing process is to protect the unit from physical damage caused by ice, snow, tree limbs, or other possible sources of harm. While some individuals advocate wrapping the entire outdoor unit with a tarp or some other type of full cover, there are disadvantages to this course of action:

  • Prevents air circulation - By sealing off the outdoor unit completely, you may trap moisture inside the unit, which can cause corrosion. Some airflow is desirable, as it keeps the unit's interior from remaining in a constant wet state.

  • Creates a habitat for animals - Another disadvantage incurred whenever you completely seal off the outdoor unit is the possibility of creating a habitat for wild animals, such as squirrels, mice, birds, or other small animals. Such small animals, particularly rodents, are notorious for chewing wiring and may do costly damage to the unit as a consequence. Leaving the unit partially open will maintain an inhospitable environment inside the cabinet and help keep the creatures away.

Instead of a full wrap, it is sufficient to cover just the top of the unit with a piece of plywood. A top cover will prevent ice or debris from entering the top of the unit but keep the sides open and allow air circulation to continue. To create a cover, measure the dimensions of the top of the unit and cut a matching square or rectangle from a piece of ½-inch thick plywood. Carefully lay the piece on top of the unit, then use a heavy object such as a cinderblock to weigh down the cover. Alternatively, you may also wish to use bungee cords to hold the cover in place.

One word of caution to keep in mind when covering your unit is this: Be sure to remove the cover in the spring or summer before you turn on the air conditioner. Blocking the airflow through the top fans could cause the system to overheat and result in major damage.

Insulate the refrigerant lines

Outdoor units are connected to the indoor evaporator coils via refrigerant lines, and these lines should remain insulated to maintain efficiency in summer and to also protect them from harsh cold weather. Insulation is available as foam wrap that is simple to install, so check with your local hardware or home improvement center to purchase some. After buying the foam, wrap it around the pipes and use cable ties to secure it in place.

For additional advice on how to winterize your AC unit, contact a local heating and air conditioning specialist.