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Air Conditioning

Coil Cleaning

  • Saves energy
  • Improves indoor air comfort
  • Reduces wear and tear on equipment
  • Complies with recommendations by equipment manufacturers
  • Should be a part of your regular maintenance plan

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.

Air Conditioning diagram

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 tubes that pass through small openings in one of the walls of the house. These metal tubes are refigerant lines.

This is how an air conditioning (refrigeration) system works. The warm air inside a house is blown through the evaporator coil, tranferring 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. It is a closed system, with the refrigerant fluid continually circulating, picking up heat indoors and releasing the heat outdoors.

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 drops significantly. Under these conditions, the system has to run longer to achieve the required cooling effect inside the house. When it runs more, it costs more and it also tends to need repair or replacement more quickly. To avoid this costly inefficiency, manufacturers of air conditioning equipment 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.

There are two kinds of coil cleaning, dry cleaning and wet cleaning. In its published, public ACR 2006 Standard (Assessment, Cleaning and Restoration of HVAC Systems) the National Air Duct Cleaning Association (NADCA) calls these two types of cleaning Type 1 (dry) and Type 2 (wet). The standard calls for a Type 1 cleaning to be carried out as a normal part of a full air duct cleaning. 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 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 the air stream blows it loose.

Wet cleanings involve two steps. First, a biodegradable enzyme- or detergent-based cleaner is applied to the coil surfaces. Second, the coil is completely rinsed to remove material dissolved or loosened by the first step.

In a DuctPro air duct cleaning, a dry or Type 1 cleaning of the indoor (evaporator) coil is automatically included at no additional charge. If a wet cleaning is needed, the technician will recommend it to you and show you why it should be done. If the outdoor (condenser) coil needs a cleaning, the technician will advise you. All outdoor condenser coil cleanings are wet process cleanings and are only done when outside temperatures are above 50º Fahrenheit.

Wet process cleanings of either indoor or outdoor coils are priced at $125 if done at the same time as a full air duct cleaning. If done as a stand-alone service, the price is $50 higher.