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Problem: Please explain the refrigeration cycle that is used in air conditioners and heat pumps?

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Problem: Please explain the refrigeration cycle that is used in air conditioners and heat pumps? How do air conditioners work? I do not understand how an air conditioner changes a vapor into a liquid? How can this cool my home?

Answer: Great question! This question and how the refrigeration cycle works in air conditioners and heat pumps is what totally excited me about learning the HVAC business! This is totally amazing how this works!  Can you imagine how excited and jubilant Willis Carrier was in 1902 when he invented the first air conditioning system! The refrigerant cycle amazes me how a high-pressure high-temperature gas vapor can be changed into a liquid in the condenser, then shot through a metering device to produce low pressure, low-temperature vapor in the evaporator to cool our homes!!! We have two really good quick YouTube videos below where AC Service Tech explains the refrigeration cycle. I explain the refrigeration cycle in more detail below the video. This really amazes me how air conditioners and heat pumps work!  If you have any questions please let us know. Our email address is

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I explain the refrigeration cycle in more detail below:

  1. The refrigeration system, your air conditioning system is a hermetically sealed system. You do not want any dirt, moisture, or foreign materials inside the refrigeration system or you will have problems over time. This is why HVAC techs evacuate the system with a Vaccum pump and install filters driers to make sure the system is clean and sealed. No leaks are a must.
  2. The compressor is the heart of the refrigeration cycle. The job of the compressor is to take a low-pressure low-temperature gas and make it into a high-temperature high-pressure gas.
  3. The compressor sends this high-temperature high-pressure gas into the air conditioner’s condensing unit where the refrigerant goes through a long series of tubing and coils where the condenser fan cools the refrigerant so that the high-temperature high-pressure vapor is cooled and condensed into a high-pressure medium temperature liquid! My HVAC teacher said to think of the refrigerant being cooled and turning into a liquid as like at night time when the air is cooled by not having the warm sun. The vapor water in the air is cooled and it comes down on the grass like dew. This made it so easy for me to understand. Yes! Water in the air is cooled at night then we have dew on the ground in the morning!
  4. This high-pressure medium temperature liquid is sent to the metering device. This metering device could be a capillary tube, TXV (thermostatic expansion valve), or a restrictor orifice. I have pictures of these three different metering devices below.
Above Cap Tube metering device.
Above TXV Metering Device:
Above Orifice Metering Device:

5. The metering device has a high-pressure liquid refrigerant (R22, R410A) on the front side and as the refrigerant passes through the metering device and is sprayed into the evaporator coil it changes the high-pressure medium temperature liquid into a low pressure, low-temperature vapor. This is where we get cooling in the evaporator coil where the liquid refrigerant is being boiled into a low-temperature low-pressure gas! I have a picture of the evaporator coil below. This is so amazing to me!

Above picture of an evaporator coil:

6. The evaporator coil gets really cold and our furnace or air handler’s blower blows our home’s unconditioned warm air across the evaporator coil where much of the heat and humidity is removed and we get that nice, fresh air-conditioned air! Thanks be to God on a hot, humid summer day!!

7. The cool gas in the evaporator is returned back to the compressor where the compressor takes the cool refrigerant gas and makes the gas into a high-temperature high-pressure gas where the refrigeration cycle starts all over again! This cycle continues on and on until your home is cool enough and the thermostat turns the AC or heat pump unit off. I hope this amazes you as much as it amazes me! If you have any questions please comment below or email us at

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