How Central Air Conditioning Systems Operate

Although central air conditioners vary from model to model, nonetheless, they operate on similar principles. The components that make up your central air conditioning system consist of the condensing unit, which is the large steel structure located outside your house. Inside the condensing unit are the air conditioner condenser coils, the compressor, and the condenser fan motor. The evaporative or evaporator coils are located in your house and are mounted on most commonly installed on top of your furnace or air handler. 

Your furnace or air handler uses a circulation blower fan that draws air through the return vent, blows it past the evaporator coils, and then forces the air through your home’s venting system. The room air in your house is then drawn back through the return vent, and your home’s airflow cycle continues. Once the air in your home has cooled sufficiently, your wall thermostat sensors will signal the circulation blower fan and a condensing unit to turn off until the room temperature in your home warms sufficiently. 

This process can be broken down into three main factors: temperature control, cooling, and air circulation. The temperature in your home is regulated by your home’s wall thermostat. Your thermostat is most likely powered by a control board or by batteries. It is important that your thermostat is in a centrally located area in your home. It should be positioned at eye level, and away from direct sunlight to reduce errors in temperature regulation. When the thermostat detects an increase in temperature, it closes the cooling circuit. This allows voltage to travel to the control board in your thermostat. The control board uses a programmed time sequence that sends 120 volts of alternating current to the blower fan motor in your furnace, and 24 volts to the condensing unit contactor to begin the cooling process. When the condensing unit contactor draws electricity, it sends 240 volts that flow to the disconnect box, then to the compressor and condenser fan motor. The disconnect box provides a way to turn off power to the condensing unit outside which contains a cartridge with fuses inside. If the compressor and condenser fan motor don’t respond, your disconnect box fuses should be tested for continuity to assess if the continuous electrical path is operating properly.

Your air conditioning compressor works like a pump by compressing refrigerant into a gas form which passes through the condenser coils, where the gas is condensed into a hot liquid. The condenser coils absorb the heat as the liquid travels through them, and then a fan is used to help the coils in this heat removal process. After the refrigerant has passed through the condenser coils, it travels to the evaporator coils on the furnace or the air handler. As the refrigerant liquid flows through the condenser coils, it turns into a gas, which cools the coils. Then the gas flows through the coils to the suction line and adheres to the compressor. The compressor changes the gas back into a liquid, and the cooling cycle resets. The water in the air condenses on the cold evaporator coils, which then rains down into a set of collection trays. The trays are usually attached to a condensate pump or a floor drain. Always remember to keep the condenser unit clean and free of debris. If the condenser unit’s coils get obstructed, the heat from them will not disperse properly and your air conditioning unit will not operate properly. Commonly people use a garden hose to clean the condenser unit by spraying water from the inside, out to remove yard debris.  

It’s important to know that airflow is the most important factor for your air conditioning unit to operate efficiently. To maintain proper airflow, your air filter should be checked monthly and replaced as required. You can buy various air conditioning filters that are 1 to 5 inches thick. Your air conditioning’s air filter should be positioned in the return or air cleaner slot. Some homes are equipped with an electronic air filter. Electronic air filters are powered by the furnace or air handler control board once the circulation blower fan is engaged. Your blower fan motor has the ability to operate at multiple speeds which can improve your air conditioner’s efficiency. Lower speeds are best when the furnace is heating (750 CFM) and higher speeds are best for air conditioning. If the circulation blower fan is loud when operating, the sound screw on the blower wheel is probably loose which causes the rotating wheel to wobble on the motor shaft. You can fix this problem by tightening or replacing the screw or replacing the blower wheel. 

The engineering design behind modern air conditioning units is fascinating. It is helpful to know how air conditioners operate if you ever need help troubleshooting any problem that may arise. Keep cool this summer, and have your air conditioning unit inspected to ensure it runs efficiently to avoid 

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