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How Do HVAC Systems Work?

Project Planning
August 10, 2017

Energy-efficient HVAC systems have plenty of moving parts, but breaking down these parts one by one can help you solve the mysteries behind this important part of your home. Learn how HVAC works by reading about the anatomy of an HVAC system.

Anatomy of an HVAC
  1. Thermostat: This is the most obvious portion of your HVAC system, and the piece you'll interact with most. Usually installed on an easily accessed walls, it can be set manually and programmed to keep your home at your ideal temperature. When the ambient temperature gets too hot or cold, the thermostat triggers your HVAC system to start circulating air as needed.

  2. Furnace: Your furnace is the star of your HVAC system, and it can be huge—it'll require the most space out of all of the different components. The furnace is designed to heat air, which is then distributed to different portions of your home via ductwork or piping. Furnaces use varied heat sources, including solar energy, heat pumps, electric resistance, and combustion.

  3. Evaporator coil: The evaporator coil is used to cool down the air when your thermostat is set to a lower temperature. This cold air is then funneled throughout your home.

  4. Condensing unit: This unit is found on the outside of your home and filled with what is called refrigerant gas. When the refrigerant is cooled, the condensing unit pumps this liquid to the evaporator coil to be transformed into gas again.

  5. Vents: These are the outlets that help distribute heated and cooled air from the duct system into the various rooms of your home. They're generally found near the ceiling with angle slats, designed to send the air downward. It's important to ensure these vents don't become blocked.

  6. Refrigerant lines: These lines carry refrigerant to the condensing unit in the form of gas. This gas is transformed to liquid form, then transferred back to the evaporator coil.

These are the basics behind the ways HVAC works. As you shop for a new HVAC system, you'll encounter a few different setups.

Types of HVAC Systems

Understanding the different varieties of HVAC systems can save you a lot of time while you're considering your options, and help you better understand how HVAC works. Narrow down your choices before you begin shopping, and get a clear picture of what you need to make yours function at its best.

  • Heating and air conditioning split system: This is the traditional type of HVAC system. It has components both in and outside of the home. Generally, it contains an air conditioner designed to cool refrigerant outside of your house, and a furnace with a fan or coil inside the house. These systems feature ductwork, which carries air throughout the various rooms of your home. Newer, energy-efficient split systems offer special accessories including air purifiers, cleaners, and humidifiers.
  • Duct-free split system: This system, as its name implies, is designed to function without ductwork. They're generally composed of a heat pump or air conditioner, a small fan coil, wires and tubing that connects the outdoor unit to the fan coil. They may also come with optional accessories, including air purifiers and cleaners.
  • Zoned systems: This type of HVAC system lets you cool or heat different areas of your home by controlling valves or dampers within the ductwork. These dampers are used to selectively block airflow. Zoned systems can save you a great deal of money, as they allow you to control which areas are heated or cooled at specific times.
  • Humidity control: Most modern systems offer optional humidity control features. Humidifiers and dehumidifiers can be added depending on your climate needs. These systems let you automatically control the humidity levels throughout your home when your HVAC system is running. In some parts of the country, humidity can be as much of a problem as high temperatures. Ever heard this weather forecast? "Temperature is 90 degrees, feels like 100 degrees." You can thank humidity for that. It's important that your cooling system provides more than cold air; your investment should offer you an overall comfortable environment, which can sometimes only be reached through humidity control.
  • Choose the right sized system: Bigger isn't always better, and this is especially true of HVAC systems. Don't purchase a larger unit than your home needs. If the system is too big for the amount of square footage it's cooling, it will cycle through its rounds too quickly. This could lead to excess condensation, mold, rot, and of course, decreased comfort.

Learn more about heating & cooling



Common HVAC Ratings and Certifications

When you're looking for a new energy-efficient HVAC system, you'll spot a variety of energy efficiency ratings on the units. To ensure you're getting the best system for your needs, it's worth knowing which systems are ranking better—that's key for getting the most out of your investment.

  • AHRI: The Air Conditioning, Heating and Refrigeration Institute is an independent lab that provides objective, accurate SEER ratings for HVAC equipment. They're tasked with certifying that a manufacturer's efficiency claims are true.

  • AFUE: This stands for Annual Fuel Utilization Efficiency, which measures the efficiency of a gas furnace used to convert fuel to energy.

  • EER: This stands for Energy Efficiency Ratio, which measures how efficiently your cooling system operates when the outdoor temperature reaches a specific level. The higher the rating, the more efficient the system.

  • SEER: This stands for Seasonal Energy Efficiency Ratio, which measures the efficiency of air conditioning and heat pump cooling. The higher the rating, the more efficient the system. The federally regulated minimum SEER rating is 13 or 14, but the ranking can go up to as high as 25.

  • HSPF: This stands for Heat Seasonal Performance Factor, which measures the heating efficiency of heat pumps. The higher the HSPF rating, the more efficient the heat pump.

  • MERV Rating: This stands for Minimum Efficiency Reporting value, which is a standard used to rate the overall efficiency of air filters. The higher the MERV rating, the finer the filtration system. Better filtration is important, as it clears the air of contaminants that your family would otherwise be breathing in.

  • NATE Certification: The NATE certification becomes important when you look to hire an HVAC technician. IT stands for North American Technician Excellence, which is a nonprofit certification program for HVAC professionals. Making sure your contractor has this certification helps ensure you're getting a qualified, skilled person for the job.

With these easy tips, you can learn how HVAC works for your family, leaving you better prepared to pick the right system for your home.

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