Dirty Coils?

There are many parts that compile a buildings HVAC/R system and the coils are one that can have many effects on the buildings conditioned air space. Coils are an integral part of any HVAC/R system and as with any main component; proper care should always be taken. For any system to run at its optimum performance having clean coils and filters is imperative.

Coils need to be clean in order to reach the units full capacity. Clean coils also allow the full efficiency, indoor air quality, and long term system performance goals to be reached. Coils which are dirty and have blocked air flow will lose significant capacity; causing the unit to run harder and longer to reach desired temperature, if at all. This causes loss of efficiency, which in turn raises energy consumption and can drastically raise a buildings energy costs.

Another side effect from a dirty coil is the decrease in unit life. Dirty coils cause the unit to run harder and longer, causing a breakdown in the compressors lubricants, leading to mechanical failure. These conditions can also lead to acid formation, which can cause acid burnout. Coils that have an accumulation of dirt cannot transfer heat, causing the compressor to run harder, this adds more heat and raises head pressures by a significant percentage. Having a higher head pressure also reduces the systems cooling capacity by a considerable amount. These conditions will be noticed most on hot days when the system is required to do the most cooling.

Coils are engineered for maximum heat transfer and are sized to match the buildings Btu cooling load. A major factor in achieving the engineered heat transfer specifications and building cooling load is dependent on the cleanliness of the coil. Coils are constantly having air transferred over them and as a result air particles are moving over them as well. These particles cause the coil to become dirty and do not allow for proper heat transfer when dirty.

The condenser coil or outside coil is commonly known as the “warm” coil because it rejects the heat using a fan to blow outside air over the coil. Outdoor coils are generally unfiltered and become a magnet for any airborne materials that may be around. If the outdoor unit or building is located in a construction area or industrial area the amount of airborne particles increases significantly. Coils which are located near high particle areas should be inspected and or cleaned more often than those which are not in these types of areas. Condenser coils should be thoroughly cleaned by a professional, licensed contractor at least once a year.

The evaporator coil is the indoor coil and is commonly known as the “cold” coil. The evaporator coil is known as the cold coil because it is the coil that provides indoor cooling for the building. This cooling is achieved by the coil absorbing hot air in the building and converting it to cold air, which is then sent throughout the buildings duct system. Indoor coils should have filters in place and filters should be changed on a regular maintenance schedule. Having dirty filters can also lead to loss of efficiency and capacity with the unit. Along with changing the filters on a schedule, filters should be checked for cleanliness and overall integrity; while changing the filters coils should be inspected for any issues. Dirty filters do not allow air to flow through to the coil for and in return negatively affect the heat dispersion.

Additionally the coil and its condensate pan can become fouled up with mold, pollen and many other particles. These conditions can negatively affect the indoor air quality of the building. Having clean filters is only part of the equation for proper system functionality. Evaporator coils are the major factor in the equation, with a clean filter and coil the energy consumption will be significantly lower.  

All coils should be cleaned by a professional contractor no less than once a year. Coils should be checked often for visible decay of the fins, dirt and any other materials that will hinder the coil efficiency. A proper coil cleaning may well result in increased capacity and lower energy consumption, resulting in a lower utility bill while increasing tenant satisfaction. In order to properly clean coils and remove all particles professionals must use particular equipment. This equipment should be used only by professionals because damage could result to coil fins if used improperly. Technicians also have an array of cleaners and agents that are designed to bring out dirt from deep within the coil. If coils are not cleaned by a professional, cleanliness and capacity of that coil may never be reached.

Coils are an extremely important part of the system, having clean coils coupled with filters can lead to lower energy bills and longer unit life. Coils as well as filters should be inspected on a regular basis and coils should be cleaned by a professional on a minimum of an annual basis. Keeping up with a buildings coil cleanings and filter changes will help out in many areas, both short and long run.