HVAC Terminology We Can Do That!

HVAC Terminology

Learn Helpful Definitions Provided by Our Expert Newnan Heating & Cooling Technicians

Below is a list of important terms and definitions related to your HVAC unit. We hope that these help you understand how to better care for your unit as well as identify when something is wrong.

To have an experienced Newnan HVAC technician inspect and perform maintenance on your unit, give us a call at (770) 766-9919 or contact us online. We’re happy to answer any questions you might have.

A-Coil: This is a heat exchanger (evaporator coil) consisting of two diagonal coils that are joined together in a manner that looks like the letter “A.”

AC: AC, A.C., or Ac may refer to air conditioning, technologies for altering the temperature and humidity of air, alternating current, or a type of electrical current in which the current repeatedly changes direction.

ACCA: This is an abbreviation that stands for Air Conditioning Contractors of America.

Acoustical: This word means of or pertaining to sound.

AC or DC: This is an abbreviation for equipment capable operating on alternating or direct current.

AFUE: This is an abbreviation for Annual Fuel Utilization Efficiency, which is a measure of a gas furnace’s efficiency in converting fuel to energy—the higher the rating, the more efficient the unit.

AGA: This is an abbreviation for American Gas Association, Inc.

Air conditioner: This is any device that can change the temperature, humidity, or general quality of the air. More specifically, an air conditioner makes your home cooler by drawing heat energy out of the house and transferring that heat to the outdoors.

Air cleaner (also air filtration system): This helps remove airborne allergens from your home.

Airflow volume: This is the amount of air the system circulates through your home, expressed in cubic feet per minute (cfm). Proper airflow depends on the outdoor unit, the indoor unit, the ductwork, and even whether the filters are clean.

Air handler: This is an air moving and/or mixing unit. Residential air handlers include a blower, a coil, an expansion device, a heater rack, and a filter. Heaters for air handlers are sold as accessories. In some models, heaters are factory installed. You can also think of it as the portion of your heating and cooling system that forces air through your home’s ductwork.

AHRI: This is an abbreviation that stands for Air Conditioning, Heating & Refrigeration Institute.

ASHRAE: The American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) is an international voluntary organization for people involved in heating, ventilation, air conditioning, or refrigeration (HVAC&R). The society promotes the general sciences of HVAC&R. The main society headquarters is located in Atlanta, Georgia with local chapters located across the United States and throughout the world. ASHRAE publishes a four-volume handbook that serves as a resource for members, with one of the four volumes updated each year. ASHRAE also publishes a well-recognized series of standards and guidelines relating to HVAC systems. ASHRAE standards are often referenced in other model building codes and the U.S. Green Building Council’s Leadership in Entry Design (LEED) green building rating system.

BTU: This is an abbreviation which stands for British thermal unit or the amount of heat required to raise or lower the temperatures of one pound of water one degree Fahrenheit. The heat extracted from your home by an air conditioner is measured in BTUs.

BTUh: This abbreviation stands for British thermal units per hour. 12,000 BTUh equals one ton of cooling.

Burner: This is a device that uses fuel to support combustion.

Burner orifice: This is the opening through which gas flows to the air/gas mixing chamber of the burner.

Burner (sealed combustion): This is a burner that obtains all air for combustion from outside the heated space.

Clean air delivery rate (CADR): This provides the number of cubic feet of clean air that a unit delivers each minute. It is the efficiency of the system times the airflow of the system.

Capacity: This is the output or producing ability of cooling or heating systems. Cooling and heating capacities are referred to in British thermal units (BTUs) per hour.

Celsius: The metric temperature scale in which water freezes at zero degrees and boils at 100 degrees, designated by the symbol “C.” To convert to Fahrenheit, multiply a Celsius temperature by 9, divide by 5, and add 32. For example, 25 x 9 equals 255, divided by 5 equals 45, plus 32 equals 77 degrees Fahrenheit.

Certified matched system: The Air Conditioning, Heating & Refrigeration Institute (AHRI) puts heating and cooling equipment through rigorous certification processes to ensure systems deliver the promised performance at certain test conditions.

CFM: This the abbreviation for cubic feet per minute, a standard measurement of airflow. A typical system requires 400 cfm of airflow per ton of air conditioning.

Charge: This means to add refrigerant to a system. This is refrigerating contained in a sealed system or the sensing bulb to a thermostatic expansion valve.

CleanEffects™ (also Trane CleanEffects™): The Trane air filtration system removes 99.98% of airborne allergens down to .1 micron from the filtered air, making it 100 times more effective than a standard 1” filter. Trane CleanEffects™ also removes over 99% of the influenza virus from your home’s filtered air according to research by the Harvard School of Public Health in collaboration with scientists at Environmental Health and Engineering Inc. (EH&E).

Climatuff® Compressor: The Trane Climatuff® Compressor was the world’s first successful heat pump compressor. To this day, it’s the only compressor Trane uses in its residential systems. It’s well known for its superior durability, low noise levels, and high efficiency.

Comfort™ coil (also evaporator or indoor coil): This is part of an indoor air unit; it functions with the air conditioner or heat pump outdoors to cool and condition indoor air that flows over it by drawing out heat and moisture.

Compressor: This is the heart of an air conditioning or heat pump system. It is part of the outdoor unit and pumps refrigerant in order to meet the cooling requirements of the system.

Condensate: This is vapor that liquefies due to the lowering of its temperature and saturation point.

Condenser coil (or outdoor coil): This is part of the outdoor portion of a heating or cooling system which releases or collects heat from the outside air.

Condenser fan: This is the fan that circulates air over the air-cooled condenser.

Contactor: This is a switch that repeatedly cycles, making and breaking an electrical circuit. When sufficient current flows through the A-coil built into the contactor, the resulting magnetic field causes the contacts to be pulled in or closed.

Crankcase heater: This is the electric resistance heater installed on compressor crankcases to boil off liquid refrigerant that may have combined with compressor oil. Many newer cooling systems do not require crankcase heaters; however, heat pumps do require them.

CSA: This is an abbreviation that stands for Canadian Standards Association.

Damper: Found in ductwork, this is a movable plate that opens and closes to control airflow. Dampers can be used to balance airflow in a duct system. They are also used in zoning to regulate airflow to certain rooms.

DB (decibels): This is a unit to measure sound.

DC: This is an abbreviation which stands for direct current electricity. This type of electricity (as opposed to alternating current, or AC) flows in one direction only without reversing polarity.

Defrost: This is the process of melting frost (as in from an air conditioner or heat pump coil).

Degree-day: A degree-day is a computation that gauges the amount of heating or cooling needed for a building. A degree-day is equal to 65 degrees Fahrenheit minus the mean outdoor temperature.

Dehumidifier: This is an air cooler that removes moisture from the air.

Diffuser: This is a grille over an air supply duct having vanes to distribute the discharging air in a specific pattern or direction.

DOE: This is an abbreviation which stands for the Department of Energy.

Downflow furnace: This is a furnace that intakes air at its top and discharges air at its bottom.

Drain pan: This is also referred to as a condensate pan. This is a pan used to catch and collect condensate (in residential systems vapor is liquefied on the indoor coil, collected in the drain pan, and removed through a drain line).

Dry bulb temperature: This is heat intensity measured by a dry bulb thermometer.

Dry bulb thermometer: This is an instrument that measures air temperature independently of humidity.

Dual compressors: This is an outdoor unit featuring two compressors, one for everyday cooling and a second one for extreme temperature days. It provides superior durability designed for cost-saving efficiency and low sound levels.

Ductwork: This is a pipe or conduit through which air is delivered. Ducts are typically made of metal, fiberboard, or a flexible material. In a home comfort system, the size and application of ductwork is critical to performance and is as important as the equipment.

DX: This stands for direct expansion or a system in which heat is transferred by the direct expansion of refrigerant.

Ecologic: This is Maytag’s designation of green heating and cooling equipment.

EER: This is an abbreviation which stands for Energy Efficiency Ratio (steady-state).

Electronic Air Cleaner (EAC): This electronically filters out magnetized airborne particles from contaminants in indoor air, sending them to a collector plate.

Energy Recovery Ventilator (also Fresheffects™ or Trane Fresheffects™): This is an energy-efficient system to exchange stale indoor air for an equal amount of fresher outdoor air.

Energy Star®: Trane’s high-efficiency systems carry the Energy Star® label. The result of Trane’s partnership with the U.S. Department of Energy and the Environmental Protection Agency (EPA), Energy Star® products are more energy-efficient and help reduce our whole earth’s pollution problems. Choosing a Trane Energy Star® Comfort System assures homeowners of lower energy bills and improved indoor air quality for their home.

EPA: This is an abbreviation which stands for Environmental Protection Agency.

Expansion valve: This is a refrigerant-metering valve with a pressure- or temperature-controlled orifice.

Fahrenheit: The temperature scale on which water freezes at 32 degrees and boils at 212 degrees designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5, and divide by 9. For example, 77 minus 32 equals 45, times 5 equals 255, divided by 9 equals 25 degrees Celsius.

Fan: This is any device that creates air currents.

Filter: This is any device that removes impurities through a straining process.

Flue: This is any vent or passageway that carries the products of combustion from a furnace.

Furnace: This is the part of the heating system in which the combustion of fossil fuel and transfer of heat occurs.

Fuse: This is a metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it. The fuse is designed to break in order to save more expensive electrical components.

GAMA: This is an abbreviation which stands for Gas Appliance Manufacturers Association.

Gas furnace heat exchanger: Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.

Heat exchanger: This is an area, box, or coil where heat flows from the warmer to the colder fluid or surface. It is the major part of the furnace that transfers heat into your home.

Heat gain: This is heat added to the conditioned space by infiltration, solar radiation, occupant respiration, and lighting.

Heating coil: This is any coil that serves as a heat source.

Heat loss: This is the rate of heat transfer from a heated space to the outdoors.

Heat pump: This is a mechanical compression cycle refrigeration system that can be reversed to either heat or cool the controlled space.

Heat transfer: This is the movement of heat energy from one point to another. The means for such movement are conduction, convection, and radiation.

HEPA filter: This is a filter that traps airborne particles by forcing air through very dense mesh.

Hertz: In alternating current (AC electricity), it is the number of cycles per second.

Horizontal flow: Often used in attics or crawl spaces, this furnace takes air from its side, heats it, and sends warm air out the other side.

HSPF: This stands for Heating Seasonal Performance Factor. This rating is used in measuring the heating efficiency of a heat pump. The higher the number, the more efficient the heat pump system.

Humidifier: This is a machine that adds water vapor to the air to increase humidity.

Humidistat: This is a humidity-sensing control that cycles the humidifier on and off.

Humidity: This is the presence of water vapor in the air.

Humidity, absolute: This is the weight of water vapor per cubic foot of dry air, expressed as grains of moisture per cubic foot.

Humidity, relative: This is the amount of moisture in the air expressed as a percentage of the maximum amount that the air is capable of holding at a specific temperature.

HVAC: This is an abbreviation for heating, ventilating, and air conditioning.

Hybrid heat (also hybrid system): This provides energy-efficient comfort for moderate heating conditions. It can use either gas or electricity.

Hybrid system (also hybrid heat): This type of system provides energy-efficient comfort for moderate heating conditions. Depending on the weather and your comfort needs, it can use either gas or electricity, with an electric heat pump as the outdoor component and a gas furnace as the indoor component.

Ignition: This is the lighting of a fuel to make it burn.

Indoor/outdoor system (also split system): This is the combination of an outdoor unit (air conditioner or heat pump) with an indoor unit (furnace or air handler). Split systems must be matched for optimum efficiency.

Inverter compressor: The air conditioner and heat pump utilize inverter technology compressors to convert the electrical current from AC to DC. In doing so, the systems almost infinitely vary the compressor and fan speed motors. The air conditioner and heat pump can modulate anywhere from 40% to 100% of capacity, instantly adjusting to exactly offset the demands on the home. Because these units do not cycle on and off like a traditional system, they save a considerable amount of energy and reduce noise levels.

Kilowatt (KW): A unit of measurement standing for 1,000 watts.

Latent heat: This is a type of heat, which when added to or taken from a substance, does not change the temperature of the substance. Instead, the heat energy enables the substance to change its state.

Load calculation: Assessed by a dealer, the calculation factors in a number of criteria in your home (square footage, number of windows, year-round weather concerns) and determines what size components you should include as part of your total comfort system.

Matched system: This system includes multiple Trane components designed and engineered to work seamlessly together to enhance overall performance, reliability, and efficiency.

Media: This is the material in a filter that traps and holds the impurities.

NATE: This is an abbreviation which stands for North American Technical Excellence, a certification acknowledging a dealer/technician as one of the most knowledgeable and experienced at installing and servicing high-performance, precision-engineered heating and cooling systems.

NEC: This stands for the National Energy Council or National Electric Code.

NEMA: This stands for National Electrical Manufacturing Association.

OEM: This stands for original equipment manufacturer.

Operating cost: This is the cost of running your home comfort system based on energy usage.

Orifice: This is an opening or hole, otherwise known as an inlet or outlet.

Outdoor coil (also condenser coil): In a heat pump, it takes in heat to warm your home. In an air conditioner, it dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid to cool your home.

Packaged system (or packaged unit): This is a single cabinet, typically installed outside, that houses both heating and cooling components.

Payback analysis: This is the number of years required before your monthly energy savings offset the original HVAC investment.

PSI: This stands for pounds per square inch.

PSIA: This stands for pounds per square inch, absolute.

PSIG: This stands for pounds per square inch gauge.

PVC: This stands for polyvinyl chloride, a type of plastic.

Reciprocating Compressor: This is a compressor whose piston or pistons move back and forth in the cylinders.

Reclaiming: This is returning used refrigerant to the manufacturer for disposal/reuse.

Recycling: This is removing, cleaning, and reusing refrigerant.

Refrigerant: This is a chemical that produces a refrigerating effect while expanding and vaporizing. Most residential air conditioning systems contain R-22 refrigerant, which is regulated under the Montreal Protocol and in the United States by the Environmental Protection Agency. R-22 is scheduled to be in production until the year 2020.

Refrigerant charge: This is the required amount of refrigerant in a system.

Refrigerant lines: These are two copper lines connecting the outdoor condenser to the indoor evaporator coil.

SEER: This stands for Seasonal Energy Efficiency Ratio, which is a measure of cooling efficiency for air conditioners and heat pumps. The higher the SEER, the more energy-efficient the unit.

SEET: This stands for Seasonal Extreme Environmental Test. It is a Trane facility that simulates a series of rigorous tests to ensure the quality/reliability of outdoor units.

Self-contained system: This is a refrigerating system that can be moved without disconnecting any refrigerant lines; it is also known as a packaged unit.

Sensible heat: This is the heat which, when added to or taken away from a substance, causes a rise or fall in temperature.

Sensor: This is any device that reacts to a change in the conditions being measured, permitting the condition to be controlled.

Setpoint: This is the temperature or pressure at which a controller is set with the expectation that this will be a nominal value depending on the range of the controller.

Spine Fin™ Coil: This is an all-aluminum outdoor coil that features the patented Spine Fin™ design. It provides greater heat exchanging capabilities (meaning higher efficiencies) and is more resistant to corrosion than a traditional copper/aluminum coil.

Thermostatic expansion valve: This is a refrigerant device that maintains a constant evaporator temperature by monitoring suction vapor superheat; it is also called a thermal expansion valve.

Thermostat: A thermostat consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system.

Ton: This is a unit of measurement used for determining cooling capacity. One ton is the equivalent of 12,000 BTUs per hour.

Two-stage compressor: This is a compressor composed of a high and low stage to increase efficiency and comfort while reducing operating noise.

Two-stage heating/two-stage cooling: Two-stage heating and cooling is considered to be more efficient because it operates at low speed most of the time. However, on days when more heating or air conditioning is required, it switches to the next stage for maximum comfort.

U-factor: This is the factor representing resistance to heat flow of various building materials.

UL: This stands for Underwriters Laboratories.

Upflow furnace: This is a furnace in which air is drawn in through the sides or bottom and discharged out the top.

Vacuum: This is a pressure below atmospheric pressure. A perfect vacuum is 30 inches of mercury (periodic symbol “Hg”).

Variable-speed motor(s): The fan motor inside Trane’s variable-speed air handlers is designed to vary its speed based on your home’s heating and air conditioning requirements. Working in conjunction with your thermostat, it keeps the appropriate temperature air (e.g. warm air on cold days) circulating throughout your home, reducing temperature variances in your home. It also provides greater air circulation and filtration, better temperature distribution, humidity control, higher efficiency, and quiet performance.

Volt: This is a unit of measure used to describe a difference in electrical potential. It is abbreviated by the symbol “v.”

Voltage: This is the force that pushes electrical current along wires and cables.

Watt: This is the unit of electrical power equal to the flow of one amp at a potential difference of one volt.

Wet-bulb thermometer: This is a thermometer whose bulb is covered with a piece of water-soaked cloth. The lowering of temperature that results from the evaporation of water around the bulb indicates the air’s relative humidity.

Zoning or zoning system: This is a method of dividing a home into different comfort zones so each zone can be independently controlled depending on use and need. It is also an air conditioning system capable of maintaining varying conditions for various rooms or zones.

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