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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 in turn 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 air conditioning unit starts out requiring that its filters be replaced. Now it needs a new compressor. Preventive maintenance or a new compressor, the better choice is clear.

In the heating mode, low airflow causes the heat exchanger to overheat. Heat exchangers are designed to operate at temperature between 120°F and 200°F. At higher temperatures, the heat exchanger oxidizes, its life-span is reduced, or it cracks and breaks. In either case, it makes far more sense to replace air filters on a regular basis.

Air conditioning 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 (blocked by dirt and dust). When the ability to transfer heat is reduced, the operating temperatures and pressures of the air conditioning 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 and energy consumption due to the increased work load. Condenser coil cleaning is included in our preventive maintenance programs.

Electrical relays are designed to open and close a certain number of times with a particular current load, before the contact points are damaged and relay requires replacement. If more than the design current is passed through this relay due to a motor working too hard, or low voltage conditions, the contact points overheat and become damaged. If the electrical contacts in a contactor (large relay) begin to get pitted, and the contactor is not replaced, eventually the air conditioners compressor motor or the fan motor controlled by the contactor will burn up and require replacement.

Once again, if we exceed the design limitations of the device, or its anticipated life span, additional damage is caused. Much more cost effective to replace a relay or contactor during a preventive maintenance when compared with a motor or compressor replacement.

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 shorter period of time by the worn pulleys. Once again during preventive maintenance we replace the belt on an annual basis to reduce the chances of needed pulley replacements.

Bearings and other rotating parts are designed to have a useful life span of hundreds of thousands of hours, provided they are lubricated at appropriate intervals and are not overloaded due to vibration from defective drive belts or dirty blower wheels. If bearings are not lubricated regularly, they will overheat and eventually seize. When this occurs, the bearings fall apart, and the blower wheel, shaft, and housing are destroyed. This is a prime example of a situation where inexpensive preventive maintenance was neglected with catastrophic results.

A unit operating with an insufficient refrigerant charge can damage its compressor via two scenarios. The unit icing up due to a low-pressure condition known as liquid slugging. Liquid slugging is when refrigerant enters the compressor as a liquid instead of the intended vapor causing irreversible damage to the compressor.

The second type of failure is when there is an insufficient refrigerant charge to cool the motor windings in the compressor. If the refrigerant charge is not sufficient, the motor within the compressor will overheat and burn up. A preventive maintenance program would spot this condition before it becomes a costly repair.

If the relative humidity is below 30% (like in the winter), the air passages in your nose and lower airways in the lungs can become dry and irritated. In people prone to asthma, this can cause an asthma attack. Also, your skin can become dry and cracked, especially if you wash your hands a lot.

Low humidity can damage wooden objects like furniture, hardwood floors, musical instruments, as the dry air sucks out the moisture contained within them.

One of the most annoying effects of dry indoor air is static shock. As you walk across a carpet or slide off upholstered furniture, a static charge builds up in your body and results in a sudden, uncomfortable “zap” of electricity when you touch a piece of metal or other conductor.

Whole house humidifiers, as opposed to portable ones which can humidify a room or two, connect directly to your furnace and work with your heating and cooling system to distribute moisture throughout your entire home.

Warm, humid summer air feels hotter than it actually is because of the moisture it contains. That same principle applies to your home in the winter. By keeping the relative humidity inside your home at an ideal level, you can turn your thermostat down a few degrees and still feel comfortable.