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Common HVAC Terms You Should Know


When it comes to the heating, ventilation and air conditioning equipment that you and your family rely on to stay comfortable throughout the year in the greater Jacksonville, Florida area, understanding various aspects of the system will be helpful during brand and model selection, installation, maintenance and repairs.

Before meeting with an HVAC technician for a consultation, going over a list of phrases that will likely come up during the conversation will save you time and help you communicate more clearly.

There's no need to become an expert on all aspects of HVAC equipment. However, the more familiar you are with common HVAC terms, the easier it will be for you to set up the best possible system in keeping with your budget and comfort requirements.

Air Exchange Rate

HVAC technicians refer to a system's air exchange rate when describing how quickly air coming in replaces the air inside the home. Technicians use air changes per hour (ACH) to calculate how many times the air is completely replaced in 60 minutes. They also use cubic feet per minute (CFM) to keep track of the total volume of outside air replacing indoor air.

British Thermal Unit

The British Thermal Unit or BTU is a term used to describe how much energy it takes to increase the temperature of one pound of water by one degree. Since this is a standard in physics, it can be used all around the world by HVAC technicians.


An air conditioning system will have a compressor installed outside the building. The compressor's job is to pump refrigerant (under pressure) to the condenser coil inside the home.

Condenser Coil

The condenser coil receives refrigerant from the compressor and extracts heat from the air inside. This waste heat is moved outside and the system continues to run until the indoor temperature reaches what you set in the thermostat.

Cubic Feet per Minute

How much conditioned air is flowing through any particular room in your home? HVAC technicians refer to the cubic feet per minute or CFM when answering this question. The more air that's flowing through the system, the sooner each room will become comfortable.

Energy Star

The U.S. government's Environmental Protection Agency or EPA established the Energy Star program in an effort to reduce our nation's usage of fossil fuel. Check for an Energy Star label to get the most efficient HVAC equipment.


Maintaining good indoor air quality is of paramount importance, especially when ill or elderly people live in the house. Install a filter that meets High Efficiency Particulate Air or HEPA requirements to remove dirt, dust, pollution and other indoor air contaminants.


Energy efficiency is crucial both for your household budget and for protecting the environment by lowering our carbon footprint. If you will use a filtration system, consult its MERV rating (Minimum Efficiency Reporting Value). The higher the MERV rating, the smaller the holes in the filter will be, enabling it to block more contaminants.


To understand how much energy a particular HVAC system will use, check out its SEER rating. SEER stands for Seasonal Energy Efficiency Ratio. The higher the SEER rating, the more efficient the system will be. Consult with your HVAC technician for advice on getting equipment with the best SEER rating for your budget.


It's important to properly size HVAC equipment for the building it's going into. Technicians calculate the tonnage for a system and measure it in increments of one-half ton. Tonnage describes the one-hour cooling capacity of any HVAC system.

Are you learning more about the common HVAC terms in use today because you are preparing to install new equipment or are in need of inspection, maintenance or repairs? The friendly professionals at David Gray Heating & Air are standing by to assist you. We will be happy to go over all the details to help you to reach a solution that's best for your family and home. For details on the HVAC services we provide or to make an appointment, please contact us today.