HVAC Glossary
Plain-English explanations of common heating and cooling terms, the same ones our technicians use when we explain what's going on with your system.
AFUE (Annual Fuel Utilization Efficiency)
A rating that measures how efficiently a furnace converts fuel into heat over a year, expressed as a percentage. An AFUE of 90% means 90% of the fuel is converted to heat, with the rest lost through venting.
Heating & Furnace RepairBTU (British Thermal Unit)
A unit of measurement for heat energy. HVAC equipment capacity is often expressed in BTUs per hour, indicating how much heating or cooling it can produce.
Manual J Load CalculationsCapacitor
An electrical component that stores and releases energy to help start and run motors in an AC or heating system. A failing capacitor is one of the most common causes of a system that won't start or runs intermittently.
Air Conditioning RepairCompressor
The component in an air conditioning or heat pump system that pressurizes refrigerant, enabling it to absorb and release heat. Compressor failure is typically one of the more significant and costly repairs in a cooling system.
Air Conditioning RepairCondensate Line
The drain line that carries moisture removed from indoor air away from the system. A clogged condensate line is a common cause of water leaks from indoor units, including ductless mini splits.
Ductless AC ServicesCondenser
The outdoor unit of a split-system air conditioner or heat pump, where refrigerant releases the heat it absorbed from inside the home.
Air Conditioning RepairDual Fuel System
A heating setup that pairs a heat pump with a gas furnace backup, using the heat pump for typical mild cold and switching to the furnace during the coldest stretches for efficiency and reliable heat output.
Related guide: Heat Pump vs. Furnace: Which Is Right for a North Texas Home?Ductwork
The system of ducts that distributes heated or cooled air from a central HVAC system throughout a home. Leaky or poorly sealed ductwork can waste a significant share of a system's output before it reaches living spaces.
Ductwork Inspection, Repair & SealingEvaporator Coil
The indoor component of an air conditioning system where refrigerant absorbs heat from indoor air, cooling it before it's distributed through the ductwork.
Air Conditioning RepairHeat Exchanger
The component in a furnace that transfers heat from combustion gases to the air circulated through your home, without mixing the two. A cracked heat exchanger is a serious safety issue that requires immediate attention.
Heating & Furnace RepairHeat Pump
A system that moves heat rather than generating it directly, providing both heating and cooling from the same outdoor unit by reversing its cycle depending on the season.
Related guide: Heat Pump vs. Furnace: Which Is Right for a North Texas Home?HVAC
Heating, Ventilation, and Air Conditioning — the systems and equipment used to heat, cool, and circulate air in a home or building.
Indoor Air Quality (IAQ)
A general term for the condition of the air inside a home, including filtration, humidity, and the presence of dust, allergens, or odors, all of which can be affected by the HVAC system.
Indoor Air Quality SolutionsManual J Load Calculation
The industry-standard method for calculating a home's actual heating and cooling load based on square footage, insulation, windows, and orientation, used to correctly size new HVAC equipment rather than guessing.
Manual J Load CalculationsMERV Rating
Minimum Efficiency Reporting Value, a scale from 1 to 20 that rates how effectively an air filter captures particles. Higher MERV ratings capture smaller particles but can restrict airflow if a system isn't designed for them.
Indoor Air Quality SolutionsMini Split
A ductless HVAC system with an outdoor condenser connected to one or more indoor units by a small line set, used to condition individual rooms or zones without central ductwork.
Mini Split InstallationPackage Unit
An HVAC system with all major components, compressor, coil, and often a furnace or heat strips, housed in a single outdoor cabinet. Common in commercial rooftop applications and some residential settings.
Rooftop Unit (RTU) Service & ReplacementRefrigerant
The chemical compound that circulates through an air conditioning or heat pump system, absorbing heat in one location and releasing it in another. Low refrigerant typically indicates a leak rather than normal consumption.
Air Conditioning RepairReturn Air
Air pulled back into the HVAC system from inside the home to be reconditioned and recirculated, as opposed to supply air, which is delivered to rooms through vents.
Airflow & Comfort DiagnosticsRooftop Unit (RTU)
A package HVAC unit installed on a building's roof, common in commercial buildings like offices, retail spaces, and restaurants, providing heating and cooling from a single weather-exposed unit.
Rooftop Unit (RTU) Service & ReplacementSEER / SEER2
Seasonal Energy Efficiency Ratio, a measure of an air conditioner's cooling efficiency. SEER2 is the updated testing standard that took effect in 2023 and uses stricter, more realistic testing conditions than the original SEER rating.
Related guide: Understanding SEER2 Ratings and What They Mean for Your Next SystemShort Cycling
When an HVAC system turns on and off in rapid, brief bursts rather than running a full cycle. It can indicate an oversized system, a refrigerant issue, or an electrical problem, and it increases wear on components.
Air Conditioning RepairSplit System
A residential HVAC configuration with an outdoor condenser or heat pump unit connected to an indoor air handler or furnace, the most common setup in North Texas homes.
HVAC System Replacement & InstallationStatic Pressure
The resistance to airflow within a duct system. Excessive static pressure, often caused by undersized or restrictive ductwork, can reduce system performance and shorten equipment life.
Airflow & Comfort DiagnosticsThermostat
The control device that senses indoor temperature and signals the HVAC system to heat or cool accordingly. Options range from basic manual models to programmable and smart thermostats.
Thermostat Installation & ReplacementTon (of cooling capacity)
A unit of measurement for air conditioning capacity, equal to 12,000 BTUs per hour. Residential systems are commonly sized between 1.5 and 5 tons depending on the home's cooling load.
Manual J Load CalculationsZoning
An HVAC configuration that divides a home into separate areas, each with independent temperature control, using dampers within the ductwork connected to a single central system.
Zoned HVAC InstallationHave a question about your own system?
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