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Central Air Conditioning 101

What is central air conditioning?


Central air conditioning is a closed system of coils that move conditioned air through a building using a network of ducts and vents. The typical central air conditioning system is referred to as a split system, meaning that it has an outdoor cabinet or Condenser (Condensing bearing unit) and an indoor component or Air Handler. The outdoor cabinet contains a fan, condenser coil and a compressor. The indoor unit contains an evaporator coil and a blower. In homes with a furnace, the air handler will be installed in conjunction with the furnace (usually on top of it) because they share the ductwork for distributing conditioned air throughout the home. We should note here that while a single unit air handler is very common, the blower and coil can be separate units. In addition, the condensing unit, coils and blower can all be housed in one single outdoor unit called a Packaged Unit which can be installed on a slab or mounted on a rooftop. Window units are miniature packaged units scaled down to fit in a window and cool a single space.


So, how does it work?


Air conditioners, and refrigerators for that matter, use a process called Phase Conversion to remove heat from the air which, in effect cools the air. Warm air from inside the home is pulled into the air handler through the return air vent. As it blows across the cold, low pressure evaporator coil, the heat energy is transferred to the refrigerant inside the coil. As the liquid refrigerant heats up, its molecules move faster and break free, changing the liquid into a gas (vaporization - the same thing happens when you boil water on the stove). The cooled air is moved into the air duct by the blower and your house is cooled. Now we have warm gas leaving the evaporator coil, but to keep the cycle going the refrigerant must be changed back so it can absorb more heat. Just as heat energy was needed to change the liquid to gas, heat energy is needed to change the gas back to liquid (condensation), that’s where the compressor comes in.


The refrigerant gas now leaves the house and heads out to the condenser where its first stop is the compressor. It’s the compressor’s job to put the gas under high pressure. This process causes more heat. The hot gas now flows into the condensing coil where the heat is released. As the gas cools, the molecules slow and the gas is converted back into a liquid state. The cooled gas is now ready to return to the air handler for more heat absorption.