We decided to create this page to offer our clients thorough, detailed glossary of heating and cooling terms, aiding you in better understanding and maintaining your HVAC system.
Air Handler: Distributes heated or cooled air throughout air conditioned space. Contains blower motor, evaporator coil, and control components. Air handlers are commonly paired as an indoor part with heat pumps or AC units. Learn about our AC services
Blower Motor: Drives airflow across the coils and through the ducts. Can be single-speed, multi-speed, or variable-speed for efficiency. Single-speed and ECM motors operate at one single speed, multi-speed and variable-speed motors adapt their operating speed in accordance with manufacturer energy saving guidelines. Schedule maintenance
Compressor: The compressor is a crucial part of your HVAC system, typically housed in the outdoor unit. It pressurizes refrigerant and enables the heat exchange cycle, which is essential for both cooling and heating your indoor space. There are two main types of compressors commonly used. A scroll compressor operates with a continuous, circular motion that compresses refrigerant smoothly and efficiently. It’s quieter, has fewer moving parts, and offers better energy performance. A reciprocating compressor, on the other hand, uses a piston moving back and forth to draw in and compress refrigerant gas. While more traditional in design, it remains reliable and widely used. Both types are integral to the performance and efficiency of air conditioning systems.
Condenser: Outdoor unit responsible for releasing indoor heat. Straight cool or heat pump condensing system facilitates conversion of refrigerant from vapor to liquid. Integral to cooling cycle; requires regular cleaning and space around it. Learn about our AC repair and heat pump repair services.
Evaporator Coil: Located inside the air handler or above furnace. Absorbs indoor heat by evaporating refrigerant. Dirty coils reduce performance. Visit our ac maintenance page to learn more and book maintenance service.
Burner: Ignites fuel (natural gas, propane, or oil) in heating systems. Must be clean for safe, efficient combustion. See our heating repair options
Heat Exchanger: Transfers heat from burners to the airflow. A cracked exchanger is dangerous and should be checked during annual inspections. Furnace troubleshooting guide.
Inducer Assembly: Improves exhaust gas flow through heat exchangers. Required in 80%+ efficient furnaces. Material depends on system AFUE rating.
Radiator: Heats rooms using hot water or steam. Part of hydronic systems, found in older homes and modern radiant floor setups. Explore radiator solutions
Gas Furnace Heating: Standard in many homes; delivers high-efficiency heat using natural gas. See Gas Furnace Services.
Electric Heat Pump: Dual-purpose heating and cooling unit. Ideal for areas without natural gas. Explore Heat Pumps.
Oil Furnace Heating: Powerful heating for older or rural homes. Oil Furnace Details.
SEER (Seasonal Energy Efficiency Ratio): Measures cooling efficiency. Higher SEER = better performance. Learn about high-SEER Carrier systems here.
AFUE (Annual Fuel Utilization Efficiency): Indicates how efficiently a furnace converts fuel into heat. Higher AFUE means less waste.
HSPF (Heating Seasonal Performance Factor): Used to measure heat pump heating efficiency over a season.
Energy Star®: Government-backed symbol for energy-efficient products. Helps reduce energy bills and environmental impact. Energy Star® is a type of certification for energy-efficient appliances approved by the EPA. The blue ENERGY STAR label delivers easy, credible, and uninvolved information that consumers and businesses rely on to make well-informed decisions.
BTU (British Thermal Unit):. A standard unit of heat. Indicates how much energy is required to raise the temperature of one pound of water by one degree Fahrenheit. Standard for HVAC sizing.
Capacity: Describes the output power of HVAC systems in BTUs or tons. Proper sizing ensures comfort and efficiency. Cooling/heating output marked in BTUs or SEER.
Matched Systems: Indoor/outdoor HVAC units tested to work together. Ensures performance, efficiency, and warranty compliance. Compatible indoor and outdoor units as per AHRI. You can check certification status on AHRI Directory of Certified Product Performance.
Downflow: A furnace that blows heated air downward, often used in attic installations.
HVAC Zoning: Uses multiple thermostats and dampers to control airflow and temperature in different areas. Divides the home into temperature-controlled zones. Increases comfort and efficiency.
Matched System: Air handler and condenser that work as a tested pair. Promotes peak efficiency. Other words, indoor and outdoor unit that are rated to work together for optimal performance.
Boiler: Produces hot water or steam for heat distribution utilizing radiant heat systems. Read more about boiler services.
Furnace: Central heating appliance powered by gas or oil. Delivers warm air through ducts by heating air and circulating it through ductwork.
Dual-Fuel: A hybrid system that combines heat pump with fossil fuel system. It can be using a heat pump and gas furnace or an oil furnace. Optimizes energy use depending on weather conditions.
Geothermal System: Transfers heat to/from the ground and uses ground temperature for heating/cooling. Geothermal HVAC is one of the most efficient systems available today. Modern cold-climate inverter heat pumps are designed to be efficient in Pennsylvania’s winters, which can vary from mild to freezing. For most homeowners in the Eastern PA the inverter heat pump offers a more balanced cost-benefit ratio with lower upfront costs and good energy efficiency.
Heat Pump: Dual-function HVAC system, for both heating and cooling, powered electrically. Ideal for moderate climates. Explore heat pump services.
Packaged Systems: All-in-one HVAC unit usually installed outdoors. Often used in commercial or mobile home settings.
Horizontal Flow: Furnace or air handler mounted on its side, for a side-to-side air movement. Ideal for tight spaces like crawlspaces or attics.
Ductwork: Network of airways that delivers heated or cooled air throughout your home. Learn more about our duct design.
Air Filter: Captures dust, pollen, and debris. Measured by MERV rating. Higher MERV = finer filtration. Improve your air quality.
Carbon Monoxide (CO): Deadly gas created by incomplete combustion. All homes should have CO detectors near fuel-burning appliances.
Humidifier: Adds moisture to indoor air for comfort and health, especially in dry winter months. Humidifier helps prevent dry skin and respiratory irritation.
UV Air Purifier: Neutralizes bacteria, viruses, and mold using ultraviolet light. UV Air Purifier is installed in HVAC ductwork.
Thermostat: Central temperature controller. Options include manual, programmable, and smart thermostat models.
Aquastat: Temperature controller in hydronic heating systems (e.g., boilers). Maintains proper water temp.
Barometric Damper: Installed in oil-fired systems. Controls flue draft for safe, efficient combustion.
Gas Valve: Controls gas supply to burners. Key safety feature in furnaces and boilers.
Lineset: Refrigerant pipes connecting outdoor and indoor units in split systems.
Filter: General term for media that removes contaminants. Could refer to air or refrigerant filters.
Programmable Thermostat: Allows users to set temperatures by time. Enhances comfort and saves energy.
Thermal Expansion Tank: Prevents pressure buildup in closed water heating systems.
Thermal Expansion Valve: Regulates refrigerant flow to the evaporator. Helps control efficiency and performance.
Maintenance: Regular inspections to clean, lubricate, and detect problems early. Get a tune-up plan.
Nitrogen Leak Test: Used to detect refrigerant leaks by pressurizing lines with inert nitrogen gas.
Power Vent Water Heater: Uses a fan to vent combustion gases horizontally or vertically through plastic PVC pipes. Power vent water heaters are much higher efficiency comparing to standard gravity units and they are great for homes without chimney access.
Refrigerant: Transfers heat in air conditioners and heat pumps. R-22, R-410A, and R-454B are the most common modern types of freon/refrigerant.
Single Stage: Operates at one capacity. Less efficient but cost-effective.
Two-Stage: Offers high and low settings for better comfort and energy use.
Boiler: Generates hot water or steam for distribution through radiators, baseboards, or radiant floor systems. Common in hydronic heating setups.
Expansion Tank: Absorbs excess pressure from heated water, protecting the boiler and plumbing from damage.
Aquastat: Controls water temperature inside the boiler and manages heating cycles. Essential for system safety.
Circulation Pump: Moves heated water from the boiler through pipes to radiators or underfloor heating.
Oil Boilers: Reliable solution for heating with hot water or steam. Oil Boiler Repair & Install.
Gas Boilers: High-efficiency options including modulating condensing models. See Gas Boiler Systems.
Radiant Floor Heating: Hydronic setup for even, silent comfort. View Radiant Heating.
Tank Water Heaters: Gas, electric, or power vented models. See Available Options.
Tankless Systems: On-demand water heating with energy savings. Explore Tankless.
Power Vent Water Heater: Uses a fan to exhaust gases horizontally. Ideal for homes without vertical venting.
Indirect Water Heaters: Uses boiler heat for water — highly efficient.
Indoor Air Handler: Wall-mounted or ceiling-mounted unit that delivers conditioned air directly into the room.
Outdoor Condenser: Removes heat from indoor spaces in cooling mode or supplies heat during the winter.
Lineset: Copper pipes and electrical wiring connecting indoor and outdoor mini-split units.
Remote or Smart Controller: Provides temperature and fan control. Often includes smart features and Wi-Fi connectivity.
Single-Zone Systems: Perfect for sunrooms, garages, or add-ons. Browse Carrier Ductless Mini-Splits.
Multi-Zone Configurations: Customized comfort in multiple rooms. Learn more about our mini-split services.
Cleaning & Maintenance: Extend life and efficiency. Mini-Split Maintenance.
Humidification & Dehumidification: Balance air moisture levels year-round. Visit our humidifiers and dehumidifiers page.
Advanced Filtration: MERV, HEPA, and electronic filters.
UV Light Purifiers: Kills bacteria, target mold, viruses, and allergens at coil level using ultraviolet light in the ductwork.
Zoning Controls: Motorized dampers and multi-thermostat comfort.
Thermostats: Manual, programmable, and smart options.
Air Filter: Captures airborne particles. MERV rating determines filtration strength.
Humidifier: Adds moisture to dry air, improving comfort and protecting wood furnishings. Learn more abut the difference of humidifier and dehumidifier.
Dehumidifier: Reduces humidity levels in the air to prevent mold growth and increase comfort.
Carrier Comfort™ Series: Budget-friendly units with quiet, reliable performance.
Carrier Performance™ Series: Mid-range with enhanced humidity and sound control.
Carrier Infinity® Series: Smart-enabled systems with Greenspeed® Intelligence. Explore All Carrier Models.
Programmable Thermostat: Allows users to set schedules for temperature changes to optimize energy use.
Zoning System: Divides home into separate zones, each with individual temperature control.
Smart Thermostat: Learns usage patterns and adjusts settings automatically for comfort and savings.
Wired/Wireless Sensor: Sends real-time room temperature or humidity data to thermostat or control panel.
A–Z Glossary Index
A – B
AHRI Certificate: A document issued by the Air Conditioning, Heating, and Refrigeration Institute confirming the efficiency ratings (SEER/HSPF) of HVAC systems as tested and matched.
Air Filter: A component that traps dust, pollen, and debris from circulating in your HVAC system.
Air Handler: The indoor unit of a split system that circulates conditioned air through the ductwork using a blower motor.
Annual Fuel Utilization Efficiency (AFUE): A rating that measures how efficiently a furnace converts fuel into heat over a season.
Aquastat: A control device in hydronic heating systems that regulates water temperature.
Barometric Damper: A device installed on flue pipes of oil-fired systems to regulate exhaust draft and maintain combustion safety.
Blower Motor: A vital component that powers airflow in your HVAC system. Available in single-speed and variable-speed options.
Boiler: A heating unit that generates hot water or steam for radiators or radiant systems.
BTU (British Thermal Unit): A standard unit of heat. One BTU raises 1 lb of water by 1°F. Used to measure system capacity.
Burner: The ignition component in gas or oil heating systems responsible for fuel combustion.
C – F
Capacity: Indicates an HVAC system’s ability to cool or heat a space, often measured in BTUs or tons.
Carbon Monoxide (CO): A toxic byproduct of incomplete combustion. All fuel-burning appliances should be monitored by CO detectors.
Central Air System: A ducted HVAC system that distributes conditioned air throughout the entire home or building.
Compressor: The core of the outdoor condensing unit that circulates refrigerant under pressure throughout the system.
Condenser: The outdoor portion of a split HVAC system responsible for discharging heat during cooling mode.
Downflow Furnace: A furnace that takes return air from the top and blows heated air downward. Common in attic installations.
Dual-Fuel System: A hybrid HVAC system combining an electric heat pump with a gas furnace for efficiency.
Ductwork: A network of insulated metal or fiberglass conduits that deliver heated or cooled air to different rooms. Learn about air duct design.
Energy Star®: An EPA-backed certification for HVAC systems that meet high-efficiency standards.
Evaporator Coil: Located inside the air handler or on top of a furnace, it evaporates refrigerant to cool the air.
Furnace: A forced-air heating unit powered by natural gas or oil. Learn more about gas furnaces and oil furnaces.
G – M
Gas Valve: Regulates natural gas flow to the burners in heating systems, providing combustion safety.
Geothermal System: An eco-friendly HVAC solution that transfers heat to or from the ground. Ideal for high-efficiency homes.
Heat Exchanger: A component in furnaces that transfers combustion heat to the circulating air.
Heat Pump: An all-electric unit that provides both heating and cooling. Learn about Heat Pump Services.
HSPF: A rating for heating efficiency of heat pumps, calculated over a typical heating season.
Horizontal Flow: A furnace mounted on its side to fit tight spaces like attics or crawl spaces.
Humidifier: Adds moisture to dry indoor air, improving comfort during winter months.
HVAC Zoning: Divides your home into zones, each with its own thermostat and damper control. Reduces energy use.
Inducer Assembly: Prepares the furnace draft for proper exhaust by pushing combustion gases to the flue pipe.
Lineset: Copper tubing connecting indoor and outdoor HVAC units. Carries refrigerant.
Maintenance: Regular inspections, tune-ups, and cleanings to extend HVAC lifespan.
Matched Systems: An indoor and outdoor unit that are rated by AHRI to work together efficiently and effectively.
N – Z
Nitrogen Leak Test: A diagnostic method that injects pressurized nitrogen into sealed lines to find refrigerant leaks.
Packaged System: HVAC systems where all components are housed in a single cabinet. Common in commercial rooftops.
Power Vent Water Heater: Uses a built-in fan to vent exhaust horizontally through walls. Great for homes without chimneys.
Programmable Thermostat: Enables scheduled temperature settings for energy savings. Also available in smart versions.
Radiator: Hydronic heating component that distributes hot water or steam throughout a space.
Refrigerant: A chemical compound that absorbs heat from inside and releases it outside, enabling the cooling cycle. R-410A has replaced R-22 (Freon).
SEER: Measures seasonal cooling efficiency. The higher the SEER, the more energy you save.
Single Stage: HVAC equipment that operates at full capacity only. Best for consistent temperature regions.
Thermal Expansion Tank: Controls pressure buildup in closed-loop water heating systems.
Thermal Expansion Valve: Modulates the flow of refrigerant into the evaporator coil for precise cooling.
Two-Stage: HVAC systems that operate at two output levels—low and high—enhancing comfort and efficiency.
