Q How often must the condenser coil be cleaned on a residential air-conditioning unit?

A Coil cleaning frequency is determined largely by the conditions the coil is exposed to. High levels of air pollution, proximity of trees and shrubs that lose their leaves seasonally and other factors will dictate how often coils will need cleaning. A coil fouled with dirt and grime cannot supply proper heat transfer resulting in higher discharge pressures and greater energy consumption. Equipment operating with dirty coils can use up to 37 percent more energy than it does with clean coils. Accumulating dirt on coils inhibits heat transfer, which makes the compressor work harder, adding more heat and raising head pressures as much as 75 percent. Higher head pressures reduce the system's cooling capacity by as much as 30 percent, a condition that is most noticeable on the hottest days when cooling is required the most. The higher temperatures and operating pressures caused by dirty coils can shorten the life of the equipment by leading to the breakdown of the compressor's lubricant. Acid formation can also occur under these conditions leading to an acid burnout. Acid formation and lubricant breakdown will adversely affect the compressor leading to equipment failure. A failed compressor means no cooling and costly repair. The condenser coil is exposed to unfiltered outside air where it can collect dust, dirt, leaves, grass clippings, animal fur, animal urine and more.While the condenser coil does not affect indoor air quality, cleaning it at the same time as the evaporator coil will result in improved energy efficiency. A coil cleaning program should be instituted when the coils are new and clean, and should be performed with a frequency that prevents deterioration of the coils. This can be as often as four times a year (monthly cleaning is reported in some areas). Annual cleaning is the bare minimum acceptable.

Question from Robert Skurski, hvacr student, Chicago. Answer by Steve Spielmann, technical manager, Goodway Technologies Corp.