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Glossary of HVAC Terms

Here are some common heating and air terms and their definitions. Knowing these terms will help you better understand your dealer's proposal.

Air Cleaner: An air cleaner is the part of your indoor air quality system that filters out harmful contaminants.

Air Conditioning, Heating and Refrigeration Institute (AHRI): AHRI is the voice for heating and air conditioning contractors and consumers. This institute maintains standards across the industry and lobbies for policy changes in government.

Air Conditioner: An air conditioner is the most common home cooling method. Air conditioners can come in either split or package system varieties.

Air Handler: An air handler is the portion of your central cooling/heating system that works in tandem with your outdoor, condensing unit to force heating/conditioned air through your home's ductwork.

Airflow: This is a measurement of the amount of air that a device is able to supply. In HVAC, airflow is measured in CFM and has implications for the effectiveness of your heating and cooling equipment. If your airflow, CFM measurement, is too low you won't be getting enough air distributed through your home, which can lead to hot or cold spots.

AFUE: AFUE is a measure of heating unit efficiency - specifically furnaces. This percentage tells you just how much energy your heating unit is converting to useful heating power - basically, the higher the number, the greater the efficiency.

BTU: BTUs are a measure of the amount of heat it takes to raise one pound of water one degree Fahrenheit. In HVAC, this typically measures the heating capacity of a furnace or air conditioner - the higher the BTU rating, the larger the heating capacity of your HVAC unit.

Capacity: Capacity refers to the ability of a heating or cooling system to heat or cool a given amount of space. Typically, heating capacity is expressed in BTUs and cooling capacity is expressed in tons. The higher the capacity, the more heating or cooling power that unit supplies.

Carbon Monoxide: An odorless, colorless gas that is harmful and deadly. Make sure to keep your carbon monoxide detector on and operational.

Certified Matched System: The Air Conditioning, Heating and Refrigeration Institute (AHRI) puts heating and cooling equipment through rigorous certification processes to ensure systems deliver the promised performance at certain test conditions. If the outdoor and indoor components of your heating and cooling systems aren't matched, you may not get expected performance levels.

Compressor: The compressor is the heart of your air conditioner or heat pump. This component is responsible for pumping refrigerant through your system. It also pressurizes the refrigerant and gets it ready for heat transfer in the condensing coil.

Condenser Coil: The condenser coil is part of the outdoor portion of your central cooling system. This system passes refrigerant through it and facilities heat transfer. It will either release or collect heat from the outside air.

Condensing Unit: Every split system cooling system contains two parts: the indoor coil/furnace/air handler and the outdoor condensing unit. The condensing unit typically contains the compressor and condenser coil (among other things).

CFM: CFM is a measure of airflow in heating and air conditioning equipment.

Damper: A valve or moveable plate used in ductwork that opens and closes to control airflow. They are used to direct air to specific areas of the home. Dampers are particularly useful in zoning systems (See 'Zone').

Demand Flow Technology (DFT): DFT is a process used by Westinghouse manufacturers to make sure that only the highest quality products leave the factory. The unit/part is checked at every part of the manufacturing process to make sure that the correct process was used prior to reaching that station.

Downflow: A type of furnace that takes cool air from the top and blows warm air to the bottom. Typically, downflow furnaces are installed in an attic.

Dry-Charged Unit: A dry-charged unit is a heat pump or air conditioner that is shipped from the factory without refrigerant.

Dual-Fuel: A dual-fuel system is any unit that is powered by electricity and gas. However, when Westinghouse says "dual fuel" we are referring to packaged heat pumps/furnaces in particular that use both electricity and gas to heat a home.

Ductwork: The air distribution system in your home is known as ductwork. Inside these hollow metal pipes air is either delivered to your rooms or returned to your system for conditioning or heating.

ecoLogic: This is Westinghouse's designation for the greenest heating and cooling equipment. These units are exceptionally energy efficient, use earth-friendly R-410A refrigerant and contain additional home comfort features that make them at the peak of HVAC quality.

Electronic Air Cleaner: Electronic air cleaners are electronic devices that filter our particles and contaminants in indoor air.

EER: EER is a measurement of cooling efficiency. Unlike SEER, EER is not the measure of cooling efficiency over a given season. EER is not typically used to label the efficiency of new cooling equipment.

ENERGY STAR: High-efficiency heating and and air conditioning equipment is rated according to ENERGY STAR efficiency standards.

Evaporator Coil: Located in either your air handler or on top of your furnace, the evaporator coil is responsible for converting liquid refrigerant into a gas. During this process, heat from air blown over the coil is transferred to the refrigerant and the cooled air is then distributed throughout the home through the ductwork.

Fixed Speed: Fixed-speed motors are the industry standard for heating and cooling equipment. Fixed-speed units maintain consistent airflow.

Formicary Corrosion: A type of corrosion caused by the combination of organic acids, water, oxygen and copper. This form of corrosion is particularly problematic for homeowner in high-moisture environments and is the leading cause of coil leaks.

Furnace: A furnace is a heating unit that uses either natural gas or oil to heat your home. In split-system applications, furnaces are typically located indoors. They also can be the heating element in gas packs or dual-fuel systems (both packaged elements).

Gas Pack: A packaged heating and cooling unit that contains all of the components of a furnace and an air conditioner.

Genuine Contractor: The top tier of contractor quality as designated by Westinghouse. These contractors offer extended warranty coverage, are up-to-date on the latest training and certifications, maintain positive reviews with homeowners, and more.

Heat Exchanger: The main part of the furnace that transfers heat into the air in your furnace, which is then distributed throughout your home through your ductwork.

Heat Pump: An HVAC unit that handles both heating and cooling. In some climates, a heat pump may be able to handle your heating and cooling needs more efficiently than a furnace and air conditioner pairing.

HEPA Filter: HEPA stands for ‘High-Efficiency Particulate Absorption’ and is a standard for the most effective air filters. HEPA filters are high-efficiency filters that block the tiniest particles from entering your home. Westinghouse includes these filters in our HEPA air cleaners.

Horizontal Flow: A type of furnace, installed on its side, which draws air from one side, heats the air and then sends it out the other side.

Humidifier: Humidifiers add moisture to air as it exits the furnace and is distributed throughout the home in order to bring up the relative humidity.

Humidity: Humidity is an indication of the amount of moisture in a given volume of air. In HVAC, humidity levels are measured in terms of relative humidity (the amount of moisture in the air expressed as a percentage of how much water can be in a volume of air at a particular temperature).

HVAC: HVAC stands for ‘Heating Ventilation and Air Conditioning.’ This term refers to any equipment, contractor, company, etc., that has to do with heating and cooling homes, business, storage compartments, etc.

IAQ: IAQ stands for ‘Indoor Air Quality’ and is the combination of air cleaners, humidifiers, filters, etc. that help improve the quality of your indoor air.

Inverter: Inverters in Westinghouse's heating and air conditioning equipment work in tandem with a rotary compressor in order to provide some of the most efficient operation in the industry. This inverter converts AC current into DC current and allows a unit to modulate at almost infinite capacities. This technology is crucial for the high-efficiency performance of Westinghouse's iQ Drive line of products.

iQ Drive: This is a line of products that is at the peak of efficiency and quality. iQ Drive products employ temperature modulation for energy-efficient performance and include air conditioner, heat pumps, air handlers and furnaces. These units also include additional home comfort and noise reduction features for premium, quiet performance.

Lineset: The lineset is the component of your central cooling system that circulates the refrigerant through the various, crucial components.

Load Calculation: Load calculations are performed to find the correct sized air conditioner, heat pump, furnace, etc. for your home.

Media Filter: A media filter catches all of the harmful particulates in your indoor air and is located in air cleaners. A media filter’s effectiveness is measured in microns.

Micro-Channel: Micro-Channel is a specific design used in coils to help combat formicary corrosion and reduce the overall weight of the unit. All-aluminum Micro-Channel coils are the most resistant against formicary corrosion. In addition, this technology requires less refrigerant and facilitates better heat transfer.

Micron: Microns are the unit of measure used to define the efficiency of a filter. The smaller the micron size, the more particles your air cleaner/filter will be able to block from your indoor air.

NATE: A technician certification network that designates the best HVAC contractors. If you are looking for contractor excellence, go with a NATE certified technician.

Packaged System: Packaged systems are one of the two types of system setups. A packaged unit combines all of your essential system components in one convenient unit. There are several types of packaged units, including: air conditioners, heat pumps, gas packs and dual-fuel systems.

R-22: R-22 is a type of refrigerant that has been used over the years in cooling equipment. Recently, it has been deemed harmful to the environment, due to its status as an HCFC, and is being phased out and replaced by R-410A refrigerant. R-22 is also known as ‘Freon.’

R-410A: R-410 is an environmentally-friendly, non-ozone-depleting refrigerant that is replacing R-22 as the acceptable refrigerant in heat pumps and air conditioners.

Refrigerant: The refrigerant flows through a central cooling system and facilitates the transfer of heat either into or out of the air that is distributed throughout your home. This chemical removes heat from the air as it evaporates and adds heat to the air when it condenses.

Rotary Compressor: A rotary compressor works like any other compressor – its job is to compress refrigerant, raising the temperature and pressure. Unlike a scroll compressor, a rotary compressor achieves compression with a roller. Typically, a rotary compressor is viewed as less efficient (when not paired with an inverter).

Scroll Compressor: The scroll compressor is a type of compressor that is typically considered the more efficient, quiet compressor. It spirals inside its cabinet in order to raise the pressure and, thereby, the temperature of the refrigerant as it passes through the outdoor condensing unit.

SEER: SEER is a measure of an air conditioner or heat pump’s cooling efficiency over a given cooling season (this is figured out by estimating how many hours your cooling system will be in operation during the season). If the unit has a higher SEER rating, it means it is more efficient.

Single-Stage: Basic heating and air conditioning units operate in one stage. This is the basic system setup.

Split System: A split system is one of the two types of system setups. A split system contains both an outdoor and an indoor component. Outdoor components include the outdoor air conditioner or heat pump condensing unit and the indoor components can include one, or a combination, of the following: evaporator coil, air handler or furnace.

Thermostat: A device that monitors and controls the temperature inside your home. Thermostats come in a variety of different types (like programmable, single stage, two stage, etc.) meaning that your thermostat must be properly matched with your heating and cooling setup to ensure proper operation.

Ton (of air conditioning): A ton of air conditioning refers to capacity in relation to melting one ton of ice in 24 hours. The capacity is measured in British Thermal Units (BTU): 288,000 BTU are required to melt one tone of ice in 24 hours (or 12,000 BTU/hr). A 2-ton air conditioner has a nominal capacity of about 24,000 BTU/h.

Two-Stage: Two-Stage HVAC systems are just as efficient as single-stage systems – the difference is in comfort level. These units have two different capacities: a higher capacity and a lower capacity. Two-stage systems are able to operate longer at the lower capacity, allowing for a better mix of air and quieter operation.

Upflow: A type of furnace that draws cool air from the bottom and blows the warmed air out the top. Typically, these furnaces are installed in basements.

Variable Speed: Variable-speed blower motors are able to provide more even temperatures throughout the home by varying the airflow in your ducts to exactly offset your heating and cooling demands.

UV Light Systems: For maximum air cleanliness, a UV light system uses the UV light spectrum to kill and control airborne microbes.

Ventilator: A ventilator captures heating or cooling energy from stale indoor air and transfers it to fresh incoming air.

Zone: Zoning allows you to control the heating and cooling delivered to specific areas of your house for a custom solution. Zoning can increase efficiency and comfort in the area of the house you use most often. Pair a zoning system with a programmable thermostat to set a reliable comfort schedule.

For any additional concerns, call a heating and air conditioning professional to get your questions answered.

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