Your complete guide to heating, ventilation, and air conditioning terminology. Understand the language of HVAC systems with clear, expert definitions.
Whether you’re researching a new HVAC system, troubleshooting an issue, or simply want to communicate better with your technician, understanding HVAC terminology helps you make informed decisions about your home comfort and energy efficiency.
This glossary covers everything from basic concepts like BTUs and SEER ratings to advanced terms used by HVAC professionals in the Portland area. For more in-depth reading, browse our HVAC education & learning guides, or explore every heating and cooling service we offer when you’re ready to put it to work.
A
A refrigeration system that uses heat rather than mechanical energy to drive the refrigeration cycle. Commonly used in large commercial applications.
The process of adjusting HVAC systems to ensure even and proper air distribution throughout a facility, optimizing comfort and efficiency.
A device that removes heat and humidity from indoor air to maintain comfortable temperatures during warm weather. AC contractor
An indoor unit that circulates and conditions air within an HVAC system, typically containing a blower, heating/cooling elements, and filters.
A measure of the cleanliness and healthiness of indoor air, affected by pollutants, allergens, humidity, and ventilation.
The movement of air through a space, driven by HVAC equipment. Measured in CFM (cubic feet per minute).
The outside air temperature and conditions surrounding a building, typically used for ventilation purposes.
An air filter designed to remove or neutralize bacteria and microorganisms from the air stream.
B
An HVAC distribution system that provides equal air volume across all zones, ensuring consistent comfort throughout a building.
A fan component in HVAC systems that moves air through ductwork and into living spaces.
A measurement of heating or cooling capacity. One BTU is the amount of energy needed to raise one pound of water by one degree Fahrenheit.
A device that controls airflow by allowing air to bypass the main air handler, helping to regulate pressure in zoned systems.
C
The maximum heating or cooling output an HVAC unit can provide, typically measured in tons (for cooling) or BTUs (for heating).
A measurement of air volume flow rate, indicating how much air moves through a system per minute.
The use of specialized chemical agents to clean HVAC components such as coils, removing buildup that reduces efficiency.
Large refrigeration machines that remove heat from liquid (usually water) via vapor-compression or absorption cycles, commonly used in commercial buildings.
A component where heat transfer occurs in HVAC systems. Evaporator coils absorb heat; condenser coils release it.
Liquid water produced as a byproduct when warm air passes over cold evaporator coils during cooling and dehumidification.
A pipe that directs condensate water away from HVAC units to prevent water damage and maintain efficiency.
The heart of an air conditioning or heat pump system that pressurizes refrigerant and circulates it through the system.
D
A movable plate in ductwork that regulates or stops airflow, used for balancing and zoning.
The process of removing excess moisture from indoor air to improve comfort and prevent mold growth.
A device that removes excess moisture from air to control humidity levels, improving comfort and air quality.
Metal or flexible tubing that distributes heated or cooled air throughout a building.
A small-scale heating and cooling system that doesn’t require ductwork, consisting of an outdoor compressor and one or more indoor air handlers. ductless mini-split installers near me
E
A rating that measures air conditioner energy effectiveness under specific conditions. Higher numbers indicate better efficiency.
A device that uses water evaporation to reduce air temperature, also known as a "swamp cooler." Most effective in dry climates.
The indoor coil in an AC or heat pump system where refrigerant absorbs heat from indoor air.
A component that reduces refrigerant pressure before it enters the evaporator coil, allowing it to absorb heat efficiently.
F
A device containing a fan and heating/cooling coil used in HVAC systems to regulate air temperature in individual rooms or zones.
A device that removes particles, dust, and contaminants from air or liquids in HVAC systems.
A brand name for refrigerant (now generic term), though many modern systems use more environmentally-friendly refrigerants like R-410A.
A heating system that uses gas, oil, or electricity to warm air, which is then distributed throughout a building via ductwork. furnace company Portland
H
A system component that transfers heat between fluids without allowing them to mix. Critical for furnace safety and efficiency.
The amount of heating or cooling needed to maintain desired temperatures in a space, used for proper system sizing.
A system that transfers heat energy using refrigeration technology. Can both heat and cool by reversing the refrigeration cycle. heat pump company Portland
High-Efficiency Particulate Air filter that captures 99.97% of particles 0.3 microns or larger, including dust, pollen, and some bacteria.
Heating, Ventilation, and Air Conditioning - the technology that provides indoor climate control and air quality.
A device that adds moisture to indoor air to prevent dryness, especially important during winter heating seasons.
I
The quality of air inside buildings, measured by levels of pollutants, allergens, humidity, and ventilation effectiveness.
Advanced technology allowing compressors to vary speeds continuously, providing precise temperature control and improved energy efficiency.
M
Regular upkeep of HVAC systems including cleaning, inspection, and tune-ups to ensure efficient operation and prevent breakdowns. AC maintenance Portland
A device that pulls fresh outside air into a building to replace air exhausted by ventilation systems.
Minimum Efficiency Reporting Value - a scale (1-16) measuring an air filter’s ability to trap particles. Higher numbers indicate better filtration.
An HVAC system connecting multiple indoor units to a single outdoor unit, allowing independent temperature control in different zones.
P
An HVAC system with all components (compressor, condenser, evaporator) housed in a single outdoor enclosure.
A central air distribution space where air collects before being distributed through ductwork.
A mobile cooling unit that can be moved between rooms, typically venting hot air through a window.
The study of physical and thermodynamic properties of air and water vapor mixtures, essential for HVAC design.
R
A compressor type using pistons driven by a crankshaft to compress refrigerant gas.
The chemical compound that circulates through HVAC systems, absorbing and releasing heat to provide cooling or heating.
Copper tubing that transports refrigerant between indoor and outdoor components of an HVAC system.
The process of heat transfer involving evaporation, compression, condensation, and expansion stages.
Air drawn back into the HVAC system after circulating through a space, to be reconditioned and redistributed.
S
A compressor type using meshing helical screws to compress air or refrigerant, common in large commercial systems.
A measure of cooling system efficiency over an entire season. Higher SEER ratings indicate better energy efficiency and lower operating costs.
The most common HVAC configuration with an outdoor condensing unit and an indoor evaporative unit connected by refrigerant lines.
Heated, cooled, humidified, or filtered air distributed throughout a building from the HVAC system.
T
An area in a building controlled by a single thermostat, maintaining uniform temperature conditions.
A device that regulates HVAC system operation by sensing temperature and controlling heating/cooling to maintain desired comfort levels. heating company near me
A unit measuring air conditioner capacity. One ton equals 12,000 BTUs per hour of cooling.
U
Technology using ultraviolet light to kill or neutralize microorganisms in HVAC systems, improving indoor air quality.
V
An HVAC system that varies the air volume delivered to different building areas based on heating/cooling demand.
An opening that allows air to pass into or out of a space, part of the ventilation system.
The process of supplying fresh outdoor air and removing stale indoor air to maintain healthy indoor air quality.
An advanced HVAC system providing precise temperature control by varying refrigerant flow to multiple indoor units.
Z
The division of a building into independently controlled temperature zones, allowing customized comfort and energy savings.
Our team at Efficiency Heating & Cooling is always happy to explain HVAC concepts and help you understand your system better.
Serving Portland Metro Area | Oregon CCB #187834
A few recent Google reviews from homeowners across the metro. We don't edit them.
Phil did a great job of carefully examining all the components of our almost 20 year old HVAC system. He took detailed photos and videos to show me the status. And he didn’t try to sell me anything else! Great experience 10/10System inspection
Efficiency Heating and Cooling came out to our home to do general maintenance on our furnace and heat pump, and also level our heat pump. Tristan was our technician. His work was efficient and thorough. He explained everything he did and told me what Efficiency H&C had to offering the way of maintenance programs. I am very happy with the services we received.Furnace & heat pump maintenance
This was my first time working with this company, and it was an amazing experience! Wayne was super personable, and explained things thoroughly and transparently. The cost was reasonable and that was with the maintenance membership program we joined. Highly recommend this business!Maintenance membership
I definitely recommend Efficiency! On this year's hottest day my AC quit working and Efficiency was able to send a technician right out. He fixed it quickly (luckily it was not a major issue) and now I'm basking in cool air. Thank you so much!AC repair
Tristan was very thorough with diagnosing the issues with my system and walked me through them so I could better understand my options for repair. We’ve had a few HVAC techs look at our system over the last decade or so, and Tristan was by far the best.System diagnosis
Jason came out for an estimate for a heat pump for my house. He listened to what I was looking for function-wise, evaluated the property, gave me a quote with 4 options, and explained the pros and cons of each. He was thorough, friendly, and not at all condescending (women, if you know, you know). Very professional.Heat pump estimate
I bought a furnace from these folks over 10 years ago and was very impressed with their work. I've had them tune up my furnace every year since and it's still the great quality and friendly service. They are dependable and knowledgeable every time I deal with them. I highly recommend them.Furnace install & tune-ups
Efficiency Heating and Cooling is a great company to work with. They gave me multiple options based on personal wants/needs with my 100+ year old house and were patient helping educate me and navigate to a decision. They were prompt, scheduling was easy, very professional, knowledgeable, and walked through with me how my system works once the job was complete. Couldn’t be happier from beginning to end and would heartily recommend them!100+ year old home
Called so many companies to find someone who did duct work beyond cleaning (I had a leak in the duct) and.so glad I got a hold of these guys. Professional, fast, and thorough. Great all around!Duct leak repair
Hire them immediately! Super fair pricing, great service. My Technician, Tristian was communicative and thorough. I tried hiring another company prior and they had me pre-pay, after tons of no shows and shoddy work followed by more no shows I demanded my money back and happily gave it to Efficiency Heating and Cooling.HVAC service
Tristan was very professional. He was on time and explained everything thoroughly. I appreciated the no pressure conversation of future work that could be done with my heating system.Heating system service
What a great experience with Efficiency. From the estimate process to installation, they made everything seamless and easy. When we hit an unexpected snag during installation, they kept us well informed about what was going on how it might affect the timeline. They got everything done and the system is working great!System installation
You'll talk to someone in our Milwaukie office, not a call center. We'll get a tech out and give you the price before any work starts.
(503) 698-5588Rather talk to someone?
