HVAC Glossary: Terms You Should Know Before You Buy

HVAC Glossary: Terms You Should Know Before You Buy

Posted by
Ed Miller on Sun, Jan 24, 2021are

HVAC systems are among the most expensive investments a homeowner will make, which is why it can quickly become overwhelming when shopping for a new one. You end up pondering questions like: Which brand do I choose? How does the unit cool the air? How do heat pumps work? And so forth…

Whether shopping for a new unit or just trying to understand what’s going on with your current one, it helps to understand certain important terms and acronyms. The more you know about HVAC, the easier it will be to make important decisions regarding your system.


There are four main types of systems, which include:

  • Ductless systems: With ductless systems, an outdoor unit is connected to an indoor unit mounted on a wall or ceiling. Ductless mini-split units are installed directly into the zones of the home that need heating and cooling. You can have as many as four indoor air handling units (four zones or rooms) for each outdoor unit. 
  • Hybrid systems: In a hybrid heating and cooling system, an electric heat pump is used in conjunction with a furnace that burns natural gas, propane, or fuel oil.
  • Packaged systems: A packaged HVAC system contains the compressor, condenser, and evaporator all in one convenient unit, often located on a roof or near the foundation. They often contain electric coils or a furnace for heating. 
  • Split systems: A split system is an outdoor unit containing the condenser and compressor, and an indoor unit containing the evaporator coil and blower. Split-system central air conditioning is the most popular type of residential heating and air-conditioning as it saves space inside your home. The indoor unit is often connected to a furnace or heat pump.

Finding the right system for your home is important; it’s not a one-size-fits-all science. The professionals at Snyder can help you find the right system for your home’s comfort needs.


Some key components that you may hear mentioned frequently include:

    • Air handler: May also be referred to as an “air handling unit,” the air handler is the indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your home. It is typically a large metal box containing elements of an HVAC system that control airflow and filtration.
    • Coil: These are what increase or decrease the temperature via heat transfer. There are two types of coils.
      • The condenser coil is in the outside air conditioning condenser unit.
      • The evaporator coil is in the indoor unit. It’s the part of an air conditioner or heat pump that absorbs the heat from the air in your house. It is located inside the air handler or attached to the furnace.
    • Compressor: An AC or heat pump compressor is the part of an outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements. There are two types – single stage and two-stage compressors.
      • Single stage compressors run at full speed to cool the hot air and shut down once the intake is no longer hot. These high-speed compressors are very quick to cool the house down but are very costly because of the voltage spikes when turning off and on, thus resulting in higher electric bills.
      • Two-stage, variable speed compressors contain sensors that allow them to make an adjustment to the compressions based on the desired temperature. They run at full speed when cooling, and slow down in order to maintain the room’s temperature. Their capability to slow down lets them conserve energy and avoid those voltage spikes. However, two stage compressors are somewhat slower at cooling the room.
    • Condensate drain line: The coil’s job is to remove humidity from the air. In doing so, it converts the humidity into water. The water drains into the drip pan and then enters the drain line. The drain line’s job is to remove the water from the drip pan and deposit it outside near the AC’s outdoor unit. They are typically made of copper or PVC.
    • Condenser: This is the outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.
  • Drip tray or pan: When warm air comes into contact with the cold evaporator coils inside your system, water drips off of those coils. The drip pan sits right underneath your system’s evaporator coils and collects all of the moisture that drips off of them. Without the drip pan, that water would drip directly onto your system and cause serious damage. The drip pan is connected to the condensate drain line, which safely drains the water outside.
  • Ductwork: The system of ducts (metal or synthetic tubes) used to transport air from heating, ventilation and air-conditioning (HVAC) equipment throughout your home.
  • Heat exchanger: A heating component that is located in the furnace and transfers heat to the surrounding air, which is then pumped throughout the home.
  • Heat pump: Part of a heating and cooling system that is installed outside of your home. It works by moving heat. During the winter, a heat pump draws heat from outdoor air and circulates it through a home’s air ducts. In the summer, it reverses the process and removes heat from the house and releases it outdoors.
  • Refrigerant: A chemical compound that produces a cooling effect while expanding or vaporizing. How it works – Air conditioners contain refrigerant inside copper coils. As refrigerant absorbs heat from indoor air, it transitions from a low-pressure gas to a high-pressure liquid. Air conditioning components send the refrigerant outside where a fan blows hot air over the coils and exhausts it to the exterior. The refrigerant then cools down and turns back into a low-pressure gas. Another fan located inside the home blows air over the cool coils to distribute the resulting cold air throughout the building.
  • Refrigerant lines: Two copper lines that connect the outdoor heat pump or AC to the indoor evaporator coil.
  • UV air purifying system: A UV system uses ultraviolet light to kill bacteria, germs, mold, and fungus. Snyder’s Fresh-Aire UV systems can provide an important layer of defense against contaminants in the air. They are installed in your ducts and are designed to disinfect the air as it circulates through the ventilation system, and have been shown to achieve up to a 99.99996% reduction in microorganisms.
  • Ventilator: a device that replaces the stale, recirculated air inside your home with fresh, filtered outdoor air. There are two types.
    • An energy recovery ventilator (ERV) is ideal for warm and humid climates, since it cools and dehumidifies the incoming outdoor air.
    • A heat recovery ventilator (HRV) is more appropriate for colder climates, as it transfers heat from recirculated air to the fresh incoming air.


Environmentally friendly HVAC systems are rapidly growing in popularity – and why shouldn’t they be? They help you cut down on energy costs and reduce your carbon footprint. When browsing eco-friendly features and energy use regulations, it is easy to become overwhelmed by the sheer volume of acronyms and terms. However, understanding the terminology can help you save money in the long run with a more energy efficient system. Let us break it down for you:

  • BTU: A measurement of heat energy. One British Thermal Unit (BTU) represents the amount of heat that is required to raise or lower the temperature of 1 pound of water by 1 degree Fahrenheit. Most air conditioners are measured using BTUs. The higher the BTU rating, the greater the heating capacity of the system.
  • BTUh: Some systems measure their energy by British Thermal Units per Hour (BTUh). The energy that is extracted from your home by an air conditioner is measured in BTUs, while the cooling and heating capacities are referred to in BTUh. For reference, 12,000 BTUh is equal to 1 ton of cooling.
  • EER: The Energy Efficiency Ratio (EER) of a cooling unit is determined by the output cooling divided by the electrical power input. As opposed to Seasonal Energy Efficiency Ratio (SEER), which is calculated over a range of outside temperatures, EER is typically determined by a set outside air temperature, a set inside air temperature and 50 percent relative humidity.
  • HSPF: The Heating Seasonal Performance Factor (HSPF) is used to measure the efficiency of a heat pump. The HSPF is a ratio of the heat output to electricity use over an average heating season. The higher the HSPF, the greater the energy efficiency.
  • SEER: Seasonal Energy Efficiency Ratio (SEER) measures air conditioning and heat pump cooling efficiency, which is calculated by the cooling output for a typical cooling season divided by the total electrical energy input during the same time frame. The higher the SEER rating, the greater the energy efficiency, and, in turn, the lower your energy cost.

Feel free to bookmark this page as a resource for your HVAC terminology questions, and if you have any questions beyond this, you can always get in touch with us!

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