3 common mistakes while covering air conditioner outdoor units

The outdoor unit is responsible for releasing the heat absorbed from indoors into the outside environment. Its casing and internal components are specifically designed to withstand harsh weather conditions.

Attempting to shield the unit can actually do more harm than good if users make any of these three mistakes:

Fully covering the unit

Many covers sold on the market are advertised as sun- and rainproof, and are often left on the outdoor units year-round. However, these covers block the air intake and exhaust vents, preventing heat from escaping and forcing the compressor to work overtime.

Prolonged operation under these conditions can damage the compressor, resulting in costly replacements. Protective covers should only be used to keep out dust during long periods of non-use, such as during winter, and must never be kept on while the unit is in operation.

Installing shelters that are too low or too close

While outdoor units do operate best in the shade, many households install shelters that are far too low or fully enclose the unit with metal panels on all sides. Thus, when the fan blows hot air out, the airflow is trapped, causing the hot air to recirculate directly back into the system. As a result, the outdoor unit has to operate with hotter air, making heat dissipation far less efficient and driving up electricity consumption.

As a general rule, a shelter should only provide shade from above. In addition, standard guidelines require the outdoor unit to be installed at least 20 cm away from the wall, with at least 60–70 cm of clear space in front of the fan.

An air conditioner outdoor unit. Photo from Pexels

Blocking the sides to shield the unit from sunlight

For outdoor units installed facing west or placed on rooftops, homeowners often place tarps or metal sheets right next to the side panels to create shade and prevent overheating. However, this reduces the airflow through the heat exchanger. A better approach is to set up a shade barrier at some distance from the unit to provide shade while leaving ample open space around it.

According to air conditioner manufacturer Carrier, outdoor units should be placed in well-ventilated areas, away from trees, debris, and obstructions. Restricted airflow due to dirt buildup is actually more harmful than direct exposure to sunlight. Leaves, litter, and dust accumulating on the heat exchanger can severely reduce airflow. Users should also keep the space surrounding the unit clean, avoiding potted plants or climbing vines nearby. When cleaning the unit, turn off the power and use a soft brush or a low-pressure water hose. High-pressure water jets should be avoided as they can bend the thin aluminum fins.

Besides, spraying water directly onto an operating outdoor unit to cool it down quickly poses a severe risk of short circuits. According to Nguyen Duc Loi, a former lecturer at the Hanoi University of Science and Technology, users can install a specialized misting system for the condenser to lower the surrounding air temperature to 30–35°C, thereby boosting efficiency. However, such systems require careful management of water volume and nozzle placement to prevent mineral buildup, he warned.