Central Air Conditioning Unit and Its Parts: A Guide Central Air Conditioning Unit and Its Parts: A Guide

For many homeowners, a central air conditioning unit is an indispensable appliance. The device works to cool, dehumidify and filter air. It is installed in a central location in the house. The air conditioning unit distributes cool air throughout the house with the aid of a heat pump and ductwork. The unit consists of several parts both inside and outside the building. Some knowledge of these parts can help you understand how the unit works.


This is the motor or engine of the unit. It is located outside the building. The compressor is about as large as a football and is usually black in color. It moves the refrigerant between the evaporator and condenser.


This is located outside the house. It consists of tubing with attached fins. The condenser is similar to the radiator in a car. It release the heat collected within the unit to the outside.


This is found inside the house. It consists of tubing usually made of copper. It feels very cold when touched because it absorbs heat from the unit.

Drip Pan

This is a tray placed underneath the air handler within the unit. It is a safety device that helps to keep your home in good shape when the air conditioning unit is operational. The pan captures the condensate that may leak from the unit. This prevents overflow of condensate into the floor or ceiling of the room where the unit is installed.

Blower Fan

It is also known as an evaporator fan. It circulates the air within the unit and distributes it to the supply ducts. The ducts then transmit the air throughout the house. Blowers may have single or variable speed.

Air Filters

These are located at the air handler unit or at the return duct air inlets. They capture the dust and debris while the unit is operational. This improves the quality of air. It is important to replace the filters periodically. This facilitates optimal performance of your unit. Clogged filters cause the unit to utilize more energy which increases your utility bills.

Reset Button

It is located in the compressor’s access panel. Occasionally, disturbances in the electrical current can cause the air conditioning unit to fail. The unit may also overheat, especially on hot days. The reset button allows you to restore the operations of the unit.


This is a regulative feature. It turns the unit on and off. It also allows you to set the desired indoor temperature.


It is a hose attached to the drip pan. The drain transmits the contents of the pan to an approved location outside the building. It may also have a float switch which shuts down the unit when the pan becomes full. You need to check the drain periodically to ensure it is not clogged. This is especially important especially during humid weather. When clogged, it lowers the efficiency of the unit.

Metering Device

It is a small tube found between the condenser and evaporator. The device determines how much refrigerant is transmitted to the evaporator from the condenser.

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