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How Do HVAC Systems Work? Expert Answers from Vancouver WA


HVAC is an acronym that stands for heating, ventilation and air conditioning. The primary function of the HVAC system is to make indoor spaces comfortable temperatures and improve indoor air quality. Both your office and your house have HVAC systems, although your office’s system is likely much more complex.

Let’s explore how the HVAC system works in your home.

Heating and Cooling Your Home in a Nutshell

Imagine a simple fan. When it’s turned on, one side of the fan pulls air and the other side pushes air. The HVAC system in your home is based on fans pulling undesirable air from inside your home and pushing heated or air-conditioned air molecules back into your home. Sometimes HVAC systems use the natural flow of the air pressure inside a room (moving from warm to cold or inside to outside) to circulate the air.

From single and multi-stage to zoned and split, there are a wide range of HVAC systems. The standard split system, with one component outside and one inside, is the most popular residential HVAC system today.

Ventilating Your Vancouver WA Home

A primary function of an HVAC system is to move air through ventilation ducts installed throughout your home.

There are two types of ventilation ducts. The return air duct pulls air from the interior of your home, and the supply air duct pushes “conditioned” (either heated, cooled or filtered) air back into your home. The magic of heating and cooling the air happens when the air travels through the furnace.

Heating Your Vancouver WA Home

Let’s say it’s another cold, wet Pacific Northwest winter, and you want to have your house temperature warmer. You go to your thermostat on the wall and set the temperature higher. The thermostat detects that the current room temperature doesn’t match your desired temperature and sends a signal to turn on the circulation blower fan in the furnace, which looks like a large metal box and is usually located in your garage, attic or closet.

The circulation blower fan sucks cool air from the house, via the return air duct, and through the filter.

Air travels through the furnace and over the heat exchanger (heated by gas burners), warming the air. The warmed air goes through the supply ducts back into the home.

Cooling Your Vancouver WA Home

Cooling your home is similar to heating, but there is an extra element: refrigerant. Similar to heating your home, when you set the thermostat to a lower temperature, the thermostat will send a signal that turns the circulation blower fan on in the furnace. It will also send another signal to the condenser unit (the enormous, unsightly box that sits outside of your house or on your roof). The signal from the thermostat turns the compressor and condenser fan on. Both are located inside of the condenser unit.

Let’s look at what happens inside the house (in the furnace) before we take a peek outside at the condenser unit.

Indoor Cooling Components

The circulation blower fan in the furnace pulls hot, wet (from humidity) air from inside the house, via the return air duct, through a filter to purify the air and protect the HVAC equipment from dust and other air contaminants.

The hot, wet air passes through the furnace and over evaporator coils. The evaporator coils are filled with refrigerant, which makes them cool. As the air molecules pass over the evaporator coils, the refrigerant absorbs their heat and the humidity in the air condenses on the cold evaporator coils. Then, the condensed humidity from the air drips down into a set of collection trays.

With the heat (energy) and moisture removed, the air will feel cool when it is returned to the inside of the house through the registers via the supply ducts.

Outdoor Cooling Components

Of course, the refrigerant will eventually get too warm to properly cool the air. When this happens, the refrigerant (which is now low-pressure warm gas) flows outside to the condenser unit. The compressor inside the condensing unit compresses the refrigerant into a tight space so it gets hotter. Then, the outside air—even though it can be 100 degrees—is drawn over the refrigerant by the condenser fan. This exhausts the heat outside of the house. Finally, the refrigerant returns to the evaporator coils as a liquid, and the cycle begins again

Keep in mind, that there are many different types of HVAC systems so heating and cooling your home might work little differently. If your HVAC system needs repairs, or you are considering installing a new system, contact a trusted HVAC expert for a consultation.