How Does an HVAC System Work?
HVAC systems are designed to move air, heating or cooling an indoor space in the process. These systems generally have three major elements: a heating unit, a cooling unit, and ducts to move the around the room. An HVAC system starts with the ventilation that brings fresh air into a building. Natural ventilation takes air from open windows, doors, or cracks and uses pressure differences to force the air through a building. With today's tightly sealed homes and offices, this requires the use of fans, blowers, filters, and ducts. HVAC and air conditioning are often used interchangeably. However, the terms actually refer to two different things. Air Conditioning Systems HVAC systems also have a cooling unit, usually an AC unit. To cool air, the fan in an air conditioning unit from HVAC Arvada, draws the air in and forces it over the evaporator’s coils. Filled with refrigerant, these coils draw heat from the air, cooling it. Next, the air moves into the air handler, where a blower sends it into the ducts. As the cool air moves through the ducts, any noxious gasses produced during the process are expelled through the flue. When an air conditioner absorbs heat, the refrigerant vaporizes. To return to its natural state, the refrigerant travels into the compressor, which pressurizes it, and onto the condenser, where it condenses from a vapor back into a liquid. As it does, it expels heat that is blown out by a fan. In some areas where it doesn’t get cold enough for a furnace, a heat pump that can both cool and heat the air is a cheaper option. Either way, these units’ cooling efficiency is measured by their Seasonal Energy Efficiency Ratio (SEER), and the cool air they produce is distributed into the house through the ductwork. For energy efficiency, you want to shop for a unit with a high SEER rating. The highest efficiency units will have SEER ratings of 20 or more, while the minimum rating is 13. To receive the U.S. government's Energy Star certification, an air conditioner must have a SEER of at least 14. Heat Pumps A heat pump works similarly to a central air conditioner and is based on the same idea that heat is always attracted to cold. To cool the air, heat is absorbed by the refrigerant and expelled out of the building. To produce warm air, a heat pump draws cold outside air over even colder refrigerant. Heat is then drawn into the refrigerant, which heats the coils. The air is drawn over those heated coils, where it rises to the desired temperature and is blown into the home. Furnaces To heat a building using a gas furnace, an HVAC system draws air in through the ducts and forces it into the furnace. When the furnace is running, the combustion chamber heats the heat exchanger to the designed temperature. Air is pushed through the exchanger, heated, and blown by the motor through the ducts and back into the house. An oil furnace like those sold by HVAC Arvada works similarly. An oil furnace pumps oil from a reserve tank through a filter and into a chamber, where it's converted into a mist and sprayed on a burner. The burner ignites, and the flame heats the heat exchanger. Just as it is with a gas furnace, air is then forced into the exchanger, heated, and blown back into the house. Oil furnaces are rare with only 5% of all HVAC systems use them. Some gas furnaces from can be modified to burn liquid propane instead of natural gas or oil. Propane furnaces are a good option for remote areas where other fuel sources might not be as reliable. Additionally, propane furnaces can fit in mechanical closets and other small spaces when square footage is scarce. Whether the furnace runs on natural gas, electricity, or propane, its efficiency is measured by its Annual Fuel Utilization Efficiency (AFUE) rating, which indicates how much fuel is converted into heat. A furnace with an AFUE rating of 95% converts 95% of the fuel supplied to it into heat. Today, the minimum acceptable AFUE rating is 80%. Particularly high-efficiency models have ratings of 95% to 98%. Each HVAC system varies depending on the heating and cooling needs of a home, where that home is located, its age, its existing ductwork, its heating and cooling needs, and other factors. Ventilation and Thermostats Some systems may also include ventilation systems that direct air out of the house, humidifiers (or dehumidifiers) that adjust the air’s humidity, and air purifiers that filter out spores, bacteria, viruses, and other minuscule particles. An HVAC tech can help you determine which of these additional components, if any, make sense for your needs. All of these are controlled by a conventional or smart thermostat. When the temperature or other criteria reach a set point, it triggers the necessary components to begin running. Some smart systems can even alert you to a problem, remind you to change the filters, and share diagnostics with your HVAC contractor.
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