Keeping your coils clean can save you operating costs, improve longevity and improve indoor air quality. This is highly recommended by the U.S. Department of Energy!
Air conditioning systems have two coils, one called the evaporator coil and a second one called the condenser coil. Coils are heat transfer devices that make heat removal possible. These coils must be kept clean to operate efficiently and provide the comfort you expect.
The evaporator coil is located inside the building, inside the ductwork, downstream from the furnace. In most homes this would mean just above the furnace, inside the plenum (the first few feet of the main supply air duct). The condenser coil is located outside the building but is connected to the evaporator coil inside the house by a pair of metal refrigerant lines that pass through small openings in one of the walls of the house.
The warm air inside a house is blown through the evaporator coil, transferring heat to the refrigerant running through the coil. This heated refrigerant is then pumped outside to the condenser coil where much of its heat load is transferred to outside air.
The efficiency of the system depends on several factors but one of the most important is the cleanliness of the coils. When the evaporator coil inside the house is clean, it picks up heat efficiently from warm inside air. When the condenser coil outside the house is clean, it disperses heat efficiently into the outside air. If either of these coils becomes dirty and partially blocked by dust and debris or by layers of mold or mildew, its efficiency and air flow across the coil drops significantly. Under these conditions, the system has to run longer to achieve the required cooling effect inside the house. It runs more, costing more and it also tends to need repair or replacement more quickly. To avoid this costly inefficiency, manufacturers of air conditioning equipment and the US Department of Energy recommend that the coils be cleaned at least annually.
Many people have service plans with their heating and cooling contractor and incorrectly assume that the coils are being cleaned during the yearly maintenance visit. This is rarely the case. If you are not sure that your coils are cleaned annually, ask about it directly. This is too important to leave to chance.
Safety King highly suggests that the evaporator coil cleaning be performed at the same time your air ducts are cleaned. There are two kinds of coil cleaning, dry cleaning and wet cleaning. In its published, public ACR Standard (Assessment, Cleaning and Restoration of HVAC Systems) the National Air Duct Cleaners Association (NADCA) calls these two types of cleaning Type 1 (dry) and Type 2 (wet). Type 2 cleanings are called for when a coil is so dirty that a Type 1 cleaning cannot restore it to acceptable efficiency.
Dry cleanings are carried out by air washing the coil. This means a technician applies a compressed air stream and/or brushes to the fins of the coil to loosen and remove impacted material. If it is an indoor coil, a powerful vacuum is also needed to collect material as it is loosened.
Wet cleanings use a biodegradable detergent of enzyme cleaner to dissolve and rinse impacted material that dry cleaning methods alone cannot effectively remove.
All outdoor condenser coil cleanings are wet process cleanings and can only performed when outside temperatures are above 50º Fahrenheit.
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