April 26, 2021

Air conditioners cool your home to comfortable levels in summer. In winter, you set the air conditioner to low and use it to reduce the humidity in your home. Basically, the system replaces the hot air in your home with cool air. This air is blown over chiller pipes by a blower fan. Inside these pipes is a coolant fluid that flows from inside your home to the AC outdoor unit. The chiller in your AC works the same way as the one in a refrigerator. When the air blows over the chiller pipes, the pipes cool that air, and it circulates back to your home. Most ACs also have a dehumidifier that removes the excess moisture in the air they cool.

The heat exchange at the chiller pipes causes the coolant to change from liquid to vapor/gas.

From the chiller pipes, the coolant, which is now warmer than it was, flows to another section. In this section, the coolant is compressed to heat it. On cold days, this part works as a heater.

The coolant flows into the outdoor unit where it releases the heat through the outdoor unit. To do this, the coolant needs to have more heat than the outdoor air. Heat will generally move from hot to cold. From there, it goes into another section where it is cooled further. After cooling, the coolant goes back into the indoor AC unit and is ready to cycle again. Read on to learn about the different mechanisms that make this cycle possible.

Refrigerant or Coolant

This is a fluid that cycles from the indoor to the outdoor AC unit continuously as long as the AC is on. The fluid transports heat from your indoor space to the outdoor space. It travels in closed chiller pipes and is ideal for use because it changes from liquid to gas fast.

When it cycles to the indoor unit, it absorbs heat from the indoor air while inside its cooling tubes. These tubes connect the inside AC unit to the outside unit. Once it absorbs the heat, it flows to the AC unit outside where it releases that heat.

As the fluid absorbs heat from the indoor space, it changes its state from gas to liquid. After releasing heat to your outdoor space, it changes back to gas and flows back inside to absorb more heat. This cycle continues until you cool your home to the desired temperature.


The compressor is the part responsible for heating the refrigerant after it has absorbed heat from the indoor AC. Inside the compressor, the refrigerant is pressurized to increase its temperature. It uses the principle that when the pressure increases, temperature also increases.

So, the compressor squeezes the liquid to increase its temperature. The increase in temperature is ideal as it facilitates the release of temperature into the outside air.

Heat moves from where it is high to where it is low, that is, from hot to cold areas. For the refrigerant to release heat into the outdoor air, it needs to be hotter than the outdoor air.

Condenser Coil

The condenser coil is the outdoor AC unit. It is in this unit that the refrigerant releases heat from your indoor space. The refrigerant is hotter than the air outside your home. So, heat naturally flows from the hot coils to the cool outdoor air.

Inside the condenser is a fan that blows outdoor air over the condenser coils. As the air blows over the coils, the heat exchange occurs, and this is how heat is exchanged. As the refrigerant loses the heat, it turns back into liquid form.

The liquid flows into the expansion valve.

This outdoor unit needs regular cleaning to ensure it runs optimally. It gathers dust and dirt more than other systems. At Gallagher's Plumbing, Heating and Air Conditioning, we can help you keep it maintained. Call and schedule routine maintenance today.

Expansion Valve

The refrigerant gets to the expansion valve in a liquid state. While the fluid has lost most of the heat at the condenser coil, it is still hot enough to raise the temperature in your indoor space. To ensure that doesn’t happen, the temperature of the refrigerant has to go down.

The expansion valve depressurizes the refrigerant to lower its temperature. This does the opposite of the compressor. Instead of compressing to increase temperature, it decompresses to lower temperature. When this happens, the refrigerant turns from liquid to gas.

The expansion valve also regulates the amount of coolant that flows to the evaporator coils. This ensures that there is always a coolant at any part of the pipes and that you only cool your home as much as you desire. Therefore, the expansion valve acts as a metering device.

Evaporator Coil

Evaporator coils are the indoor AC unit. The refrigerant absorbs heat from your indoor space inside these coils.

The copper tubes in the coils receive the cold refrigerant from the expansion valve. Your indoor blower fan blows the hot indoor air over the cold copper tubes. When this happens, the refrigerant absorbs the heat from your indoor air and cold air is fanned into your living space.

Just before the sucked air gets into the evaporator coil, it passes through a filter that traps particles. This way, your air is cleaner and cooler for your comfort. Most air purifiers, including REME HALO and UV lamps, install in central AC just before the evaporator coil.

The refrigerant absorbs heat from your indoor air and changes into a gas.

Window air conditioners also have all the parts above but in a compact unit. Instead of the indoor and outdoor units, the window air conditioner has the room side and the outdoor side. The room side has a grille that sucks indoor air. The outdoor side facilitates the heat exchange between the indoor and the outdoor air.

Other Parts

Smaller parts such as filters, fans, thermostats, and mufflers also play a special role in the functioning of the air conditioner.

The filters trap dust to keep your indoor air clean. You need to clean or replace these regularly to make them efficient. Again, you need to get the best quality HEPA filters to ensure you trap even the smallest particulates.

Thermostats are the watchdogs of your AC system. They detect the temperature in the indoor air and slow down or switch off the AC. When the indoor air gets to the desired temperature, the thermostat slows down the AC. When the temperature increases above the desired temperature range, the thermostat brings the AC back up.

Mufflers reduce the noise coming from the compressor and other parts. Without a muffler, the system would be uncomfortably loud. Your system has two main fans, the blower fan near the evaporator coil and the condenser fan. The blower fan is responsible for circulating cold air in your home and blowing hot air over the evaporator coils.

Professional Help

At Gallagher's Plumbing, Heating and Air Conditioning, we offer installation, repairs, and maintenance of the heating and cooling systems. We also sell products to our customers in North Valley and Greater Sacramento, which include air conditioners, furnaces, and packaged systems among others. Call Gallagher's Plumbing, Heating and Air Conditioning today and check your financing options.

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