Have you ever wondered exactly how your home’s heating or air conditioning works? HVAC systems are far more complex than many people realize and have numerous components. They all work together to heat up or cool down the air inside a building. Here, we’ll explain what all of the components of an HVAC system are, what role they serve and how different types of heating and air conditioning work.
Thermostats
The thermostat is essentially the brain of an HVAC system and tells it when to turn on and off. Most thermostats are set so that they will signal the system to run. This happens when they sense that the temperature in the building is between 1 and 3 degrees Fahrenheit above or below whatever temperature they are set to. The thermostat will then signal the system to shut off as soon as it senses that the air is at the desired temperature.
Older manual thermostats sense temperature using mercury, but modern digital thermostats use a special type of semiconductor known as a thermistor. A small amount of electricity constantly flows through the thermistor, which constantly monitors the amount of electrical resistance the current encounters. The amount of electrical resistance is directly impacted by temperature. As temperature increases, resistance decreases and vice versa. As long as the thermostat is calibrated correctly, it can accurately determine the temperature of the air around it by monitoring changes in resistance.
HVAC Ductwork and Blowers
In a central HVAC system, the ductwork and blower work together to circulate warm or cool air around the home. Ductwork systems consist of two separate parts: the supply ducts and return ducts. The blower draws air in through the return vents. It then travels through the return ductwork to either the furnace or the air handler where the AC evaporator coil is located. After the air is heated or cooled, it then travels through the supply ductwork and gets blown out of the supply vents in each room.
For a central HVAC system to work effectively, the blower must be able to constantly circulate a certain volume of air. Exactly how much air the system needs to circulate depends entirely on the size of the furnace, air conditioner or heat pump. If a home’s ductwork isn’t properly sized or not installed properly, the system won’t be able to move a sufficient volume of air for it to heat or cool effectively.
Central Air Conditioning and Heat Pump Systems
Central air conditioning and heat pump systems are fairly complicated and work by using a special chemical called refrigerant. This captures heat from the air in one location and then transfers and releases it into another location. In an air conditioning system, the refrigerant naturally pulls heat out of the warm air constantly being drawn over the evaporator coil. The hot refrigerant then gets pumped outside and into the AC compressor.
Compressing the refrigerant causes it to boil and turn into a “superheated” gas that is somewhere around 120 to 140 degrees Fahrenheit. The refrigerant then flows through the condenser coil. As the system runs, the compressor fan constantly draws air into the unit so that it blows over this coil. Since the refrigerant is generally hotter than the air, all of the heat stored in the refrigerant gets naturally released and flows into the air.
This process leads to the refrigerant changing back into a liquid before it flows out of the condenser coil. However, the refrigerant still contains quite a bit of latent heat at this point. Before being pumped back inside the building, the refrigerant first flows through an expansion valve. This results in its pressure instantly decreasing and causes it to become much colder than the air inside the home. This is so that it is again able to naturally pull heat out of the air.
The difference between a standard air conditioner and a heat pump is that a heat pump can run in reverse to provide heating. This means that the indoor and outdoor coils reverse roles so that the refrigerant captures heat from the air outside and releases it into the air inside. What many people don’t understand is that air always contains at least some heat energy no matter how cold it is. As long as the refrigerant is colder than the outdoor air temperature, it will still be able to capture heat. Depending on the type of refrigerant used, most heat pumps can keep working and transferring heat inside in temperatures as cold as -10 to -22 degrees Fahrenheit.
Central Heating Systems
Central heating that runs on a furnace is known as a forced-air heating system. This type of system obviously works by adding heat to the cooler air being brought in by the blower. When the furnace is running, the flames produced by its gas burners create extremely hot combustion fumes. The furnace’s draft inducer fan draws the hot fumes out of the combustion chamber and into the metal heat exchanger. Since metal is such a great conductor of heat, the heat exchanger absorbs the majority of the heat from the fumes as they flow up through it. As the blower draws cooler air over the heat exchanger, much of this heat naturally flows out of the metal to instantly make the air much hotter. This process is so effective that the air quickly gets heated to somewhere around 120 to 140 degrees Fahrenheit, which allows the system to quickly raise the temperature of the home.
Furnaces are either conventional or high-efficiency condensing units. The difference between the two is that condensing furnaces have a primary and secondary heat exchanger whereas conventional units only have one. Heat exchangers can only absorb so much heat at a time. With a conventional furnace, the combustion fumes retain quite a bit of latent heat when they flow out of the heat exchanger and are vented outside through the exhaust flue. As a result, conventional furnaces waste somewhere between 11% and 20% of the energy they consume.
Condensing furnaces are much more efficient and only waste between 2% and 10% of the energy they use. The reason that they are called condensing furnaces is that they absorb so much heat from the fumes before they’re vented outside. Then, they become cold enough for the water vapor they contain to condense into liquid. This is why condensing furnaces have a condensate drain system that collects this water and transports it away from the furnace either into a floor drain or outside the house.
Ductless HVAC Systems
Ductless HVAC systems, also called ductless mini-splits, are a unique type of system that is self-contained. These systems can run on an AC condenser or a heat pump that is connected to one or more air handler units inside the building. Instead of having a central blower, each air handler has its own blower that pulls in air from the surrounding area and blows it back out after heating or cooling it. As with a central system, the air handlers have a coil that uses refrigerant to either remove heat from the air or add heat to it.
If you need the help of an experienced, trustworthy HVAC company, look no further than Titanz Plumbing & Air Conditioning. We’ve been serving customers in Port Charlotte and throughout Southwest Florida since 2007. We specialize in the full range of heating and air conditioning services and are ready to handle your installation, repair and maintenance needs. For more information on what makes us the area’s best choice for HVAC and plumbing, give us a call today.
