Furnace Repair Service San Marcos TX | AirOne Heating and Air Conditioning

How AC Systems Work

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Heat pumps and most central air conditioners are called “split systems” because there is an outdoor unit (called a condenser) and an indoor unit (an evaporator coil). The job of the heat pump or air conditioner is to transport heat from one of these units to the other. In the summer, for example, the system extracts heat from indoor air and transfers it outside, leaving cooled indoor air to be recirculated through your ducts by a fan.

heat pumps and air conditioners

A substance called a refrigerant carries the heat from one area to another. Basically, here’s how it works:

Most people think that air conditioners lower the temperature in their homes by pumping cool air in. The actual process removes warm air from your house and cycles it back in as cooler air. This cycle continues until your thermostat reaches the desired pre-set temperature. Your cooling system works like a big sponge. The refrigerant in the system absorbes the heat inside your house and the outside condenser squeezes that heat out into the air outside your home.

System elements include a compressor, a fan, condenser coil, evaporator coil, and a refrigerant. The unit extracts heat from indoor air and transfers it outside, leaving the cooled indoor air to be re-circulated.

The compressor in your outdoor unit will change the gaseous refrigerant into a high temperature, high-pressure gas. As that gas flows through the outdoor coil, it loses heat. That makes the refrigerant condense into a high temperature, high pressure liquid that flows through copper tubing into the evaporator coil located in your fan coil unit or attached to your furnace.

At that point, the liquid refrigerant is allowed to expand , turning the liquid refrigerant into a low temperature, low pressure gas. The gas then absorbs heat from the air circulating in your home’s ductwork, leaving it full of cooler air to be distributed throughout the house. Meanwhile, the low temperature, low pressure refrigerant gas returns to the compressor to begin the cycle all over again.

While your air conditioner or heat pump cools the air, it also dehumidifies it. That’s because warm air passing over the indoor evaporator coil cannot hold as much moisture as it carried at a higher temperature, before it was cooled. The extra moisture condenses on the outside of the coils and is carried away through a drain. The process is similar to what happens on a hot, humid day, when condensed moisture beads up on the outside of a glass of cold lemonade.

An air conditioner is basically a refrigerator without the insulated box. It uses the evaporation of a refrigerant to provide cooling. The mechanics of the refrigerant evaporation cycle are the same in a refrigerator as in an air conditioner. A compressor compresses cool refrigerant, causing it to become hot, high-pressure gas. This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid. The liquid then runs through an expansion valve, and in the process it evaporates to become cold, low-pressure gas. This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the home.

Three elements which make up a split central air conditioning system, are:

  • An outdoor condensing unit
  • A matching indoor air handler
  • Ductwork to transfer the cooled air throughout the home

The same process works in reverse in a heat pump during the winter. The heat pump takes heat out of the outside air – or out of the ground, if you have a geothermal heat pump – and it moves that heat inside, where it is transferred from the evaporator coil to the air circulating through your home.

That’s not a typographical error, by the way- the heat pump moves heat from outside to warm your home, even on a cold day. That’s because “cold” is a relative term. Air as cold as 30 degrees still contains a great deal of heat – the temperature at which air no longer carries any heat is well below -200 degrees Fahrenheit. A heat pump’s heat exchanger can squeeze heat out of cold air, then transfer that heat into your home with the help of a fan which circulates the warm air through your ducts.

Heat pumps are often installed with back-up electric resistance heat or a furnace to handle heating requirements when more heat is needed than the heat pump can efficiently extract from the air.

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