I assume you have a split-coil central air conditioning system.
- The evaporator is located in the furnace plenum and the condenser is located outdoors.
- The condenser is designed to be out in the elements.
- Wind, rain or snow should not negatively affect the condenser.
Protection during winter months
Many stores sell covers for use during winter months, but I don't recommend them since they encourage rodents to nest in the sheltered housing.
If ice fall from the building is a potential hazard, you can always lay a flat piece of 3/4" exterior grade plywood on top of the condenser to disperse the force of falling ice over the entire top of the unit.Make sure you tie the board down so it doesn't blow away during high wind conditions.
Preparing for hot weather
Most condenser units pull air through the sides of the coil and dispense it through the top. You can verify this by feeling the air coming off the top of the unit. If it is warm, it is discharge air.
- Make sure that the top is not obstructed and that the side fins are cleaned before the cooling season and after a major pollen event.
- A soft brush or gentle washing can clean the surface of the coils.
- Make sure you do not drive the surface dirt and debris into the coils by using high-pressure water perpendicular to the coils (fins).
Shading from summer sun
If you want to shade a condenser that is located in a sunny area to improve efficiency, you could build a shed roof screen on four posts to shade the unit during peak sun hours.
Alternatively, you could plant a "green" screen as long as there is adequate distance between the condenser and the screen to prevent any obstruction to the air. Make sure you plant a variety of plants that do not produce heavy pollens, sap, or debris.
Your local landscape professional could advise you what might be appropriate in your location.