Why must we replace air filters?
Air conditioning equipment is designed to operate with a specific quantity of air passing over its indoor coil surface. When air filters are not replaced, they clog and become coated with dirt. Similarly, the indoor coils get coated with dirt. This dirt reduces the amount of air through the unit below the design limit, leading to catastrophic failure.
In the cooling mode, if there is not enough air over the indoor coil, the coil temperature drops. When it drops below the freezing point, ice forms on the coil, which further reduces the airflow, which further reduces the coil temperature. The compressor within the unit is a pump, which is designed to pump a vapor. As the airflow through the indoor coil drops, there isn't enough heat being removed from the air passing over the coil to vaporize the liquid refrigerant inside the coil. Thus, instead of receiving a vapor, the compressor receives liquid refrigerant. This is called "liquid slugging". The effect of "liquid slugging" is similar to the effect of pouring liquid into the cylinders of a gas engine. As liquids are not compressible, cylinder pressure exceeds the design limits, of the cylinder, and the valves, connecting rods, pistons, or other internal components are destroyed. The units start out requiring that its filters be replaced. Now it needs a new compressor.
Why must we replace drive belts? ( usually Commercial )
Loose or broken drive belts cause the same problems that dirty filters cause. They cause the airflow through the equipment to be reduced below design limits. In addition, loose drive belts slip on the pulleys. This wears the groove in the pulley so that when the belt is replaced, the new belt is ruined in a short period of time by the worn pulleys. Once again replace the $15.00 "or" so belt on a regular basis or spend much more replacing pulleys.
Why must we clean condenser coils?
Equipment is designed to operate between certain outdoor temperature limits. Cooling and condensing of the refrigerant vapor is designed to occur with a particular volume of air flowing through the condenser at a maximum outdoor ambient temperature. (Usually 115°F) If the finned surfaces of the outdoor coils are fouled with dirt, the ability of these coils to transfer heat is reduced and the airflow through the condenser coil is reduced. When the ability to transfer heat is reduced, the operating temperatures and pressures of the unit increase. A unit, designed to operate at ambient temperatures of 115°F or more, may stop operating at an outdoor temperature of 90°F. Due to the reduced heat transfer capability, the operating temperatures and pressures within the unit exceed the manufacturer's safe limit and the unit shuts down. If the unit does not exceed the manufacturer's limits by enough to shut down, it will continue to run at reduced capacity and efficiency, and at an increased rate of wear due to the increased work load.