AFUE
Annual Fuel Utilization Efficiency is a measurement used to rate furnace efficiencies by dividing the ratio of heat output by heat input.
AGA
American Gas Association, Inc.
AHRI
The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) is the trade association representing manufacturers of HVACR and water heating. Their website can be found at http://www.ahrinet.org/Home
Air Conditioner
A device that changes humidity levels, temperature or quality of air.
Air Handler
This is the unit inside the house that circulates air through the duct system. It is paired with a split system air conditioner or heat pump. This is the box that contains the blower. It also usually contains the evaporator coil and other heating/cooling elements
Airflow Volume
Measured in cubic feet per minute (cfm), this is the amount of air circulated in a space.
Air Handler
Indoor part of the air conditioning system including the circulating fan and evaporator (summer) / condenser (winter) coil.
BTU
A British Thermal Unit is a measurement of the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit.
BTU/h
British Thermal Units per hour
Burner
The device that facilitates the combustion of air and gas
Capacity
HVAC capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.
Celsius
A temperature scale that registers the freezing point of water as 0° and the boiling point as 100° under normal atmospheric pressure.
CFM
Cubic Feet per Minute, a measurement of airflow volume.
Charging a System
Adding coolant, or refrigerant, to an HVAC system.
Coil
The coil, or evaporator coil, is connected to the airflow outlet of the furnace. Conditioned refrigerant is circulated through the coil to cool the structure in the summer and heat in the winter. As warm indoor air passes through the indoor or evaporator coil, temperature and humidity are removed creating cooler indoor air. Installing a correctly sized and rated evaporator coil is essential for getting the highest performance and comfort from your central air conditioning or heat pump system.
Compressor
A pump that increases the pressure of refrigerant gas. This is the part of the air conditioner that sits inside the condenser. When you hear a lot of noise coming from your system, this is likely where that noise is coming from. It is responsible for circulating and raising the pressure of the refrigerant in your system.
Condensate
As warm air is pulled or pushed across the cool evaporator coil the coil perspires, creating liquid, or condensate which is mechanically drained away from the equipment.
Condenser Coil
Generally, the outdoor coil, it removes heat from the refrigerant in the summer months, allowing the refrigerant to be converted from vapor to liquid and complete the refrigeration process.
Condenser Fan
A fan that accelerates the movement of air over the condenser coil, facilitating the removal of heat from the refrigerant.
Degree-Day
Calculated by subtracting the average outdoor temperature for an area from 65º Fahrenheit. This measurement is used to estimate the amount of heating or cooling a home or building will need.
Dehumidifier
A device that removes humidity, or moisture, from the air.
Diffuser
A grille over an air supply duct with vanes that distribute the discharging air in a specific pattern or direction.
DOE
Department of Energy. Their website can be found at https://www.energy.gov.
Downflow Furnace
A furnace with an intake on the top and an air discharge at the bottom.
Drain Pan
Also a condensate pan. As the refrigerant vapor is liquefied, the drain pan collects the condensate and funnels it to the drain line.
Dry Bulb Temperature
The temperature as measured without the consideration of humidity.
Duct work
A network of metal, fiberboard or flexible material flowing throughout a space which delivers air from an HVAC unit to the respective zones of a home or office.
EER
The Energy Efficiency Rating of a particular cooling device is the ratio of output cooling energy (in BTU) to input electrical energy at a given operating point.
Energy Star®
ENERGY STAR is a U.S. Environmental Protection Agency (EPA) voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency. Energy Star’s website is https://www.energystar.gov/.
EPA
The United States Environmental Protection Agency is an agency of the US federal government which was created for the purpose of protecting human health and the environment by writing and enforcing regulations based on laws passed by Congress. Their website can be found at https://www.epa.gov/.
Evaporator Coil
Also an indoor coil. A device that is designed to absorb heat in the air in order to change the liquid refrigerant that flows through it into a vapor initiating the cooling process.
Expansion Valve
A valve that meters the levels of refrigerant through a temperature or pressure control.
Heat Exchanger
A device through which heat is transferred to a cold or warm area or surface.
Heat Gain
The amount of heat added or created in a designated area.
Heating Coil
A coil that acts as a heat source for a heating system.
Heat Loss
The amount of heat lost or subtracted from a designated area.
Heat Pump
A device used for either the heating or cooling of a space by transferring heat between two reservoirs. A heat pump looks like a normal air conditioning condensing unit, but it can use electricity to efficiently heat your home in the winter and also cool your home in the summer just like a standard air conditioning system.
Heat Transfer
The flow of heat from one area to another by conduction, convection, and/or radiation. Heat flows naturally from a warmer to a cooler material or space.
HSPF
The Heating Seasonal Performance Factor (HSPF) is a term specifically used to define the measurement of efficiency of a residential heat pump system.
Humidifier
A device that adds humidity, or moisture, to the air.
Humidistat
The device that measures humidity and turns the humidifier on and off.
Humidity
Dampness in the air caused by water vapor.
Latent Heat
Is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process that creates a change of state. An example is the latent heat of evaporation which creates a phase transition from liquid to a vapor at a specified temperature and pressure.
Line Set
These are the two lines of refrigerant that connect the evaporator coil and condensing unit. The small, copper tube is the liquid line, while the large and more insulated tube is the suction line.
Load Calculation
This calculation determines how much heating or cooling your home needs. Your HVAC technician does a load calculation to determine how much heat is gained or lost in order to properly size the system that you need for your home.
MERV
This stands for Minimum Efficiency Reporting Value. This is how a filter is rated for your system. The higher the rating, the more efficient a filter is. Generally, the highest rated filter is MERV 16, which is a hospital quality filter that captures the smallest of particles in the air. For more on MERV ratings, check out our post that covers MERV ratings in more detail.
Package Unit
A heating and cooling system contained in one outdoor unit.
Particulates
The fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood stoves, etc are regulated by the U.S. Environmental Protection Agency.
Plenum
A pressurized housing containing a gas (typically air) at positive pressure (pressure higher than surroundings). One function of the plenum is to manage and equalize pressure for more even distribution. This is the box that is attached to the side of the air handler where the other ducts are attached. On the side that has the return, you may find that there is a filter between the air handler and the plenum. On the side that has the supply, you may see the evaporator coil that is separately housed from the blower. The plenum is usually made of insulated sheet metal, but could be made of other materials.
Programmable Thermostat
A type of thermostat that allows the user to program into the devices’ memory a pre-set schedule of times and temperatures enabling or disabling the HVAC equipment.
PSI
A pound per square inch is a unit of pressure resulting from the force of one pound-force applied to an area of one square inch.
PSIA
Pounds per square inch, absolute is used to clarify that the pressure is relative to a vacuum rather than the ambient atmospheric pressure. Since atmospheric pressure at sea level is around 14.7 psi, this will be added to any pressure reading made in air at sea level.
PSIG
Pounds per square inch gauge designates that the pressure is relative to atmospheric pressure.
Psychometric
The analysis of atmospheric conditions, particularly moisture in the air.
Refrigerant
The compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space. This fluid boils at a very low temperature enabling it to exude and absorb heat.
Refrigerant Charge
The amount of refrigerant in a system.
Register
This is the cover over the inlets and outlets of your ductwork. It has louvers that lets the user control the airflow.
Scroll Compressor
Used in both lower and higher efficiency air conditioners, scroll compressors are popular because they feature fewer moving parts than reciprocating compressors. This translates to more efficient operation, higher tolerance to liquid refrigerant, less mechanical failure and smoother, quieter operation.
SEER
The efficiency of air conditioners is often rated by the Seasonal Energy Efficiency Ratio which is defined by the Air Conditioning, Heating, and Refrigeration Institute as the cooling output during a typical cooling-season divided by the total electric energy input during the same period. This measures the efficiency of an air conditioner. This is calculated by taking the BTU/hour of cooling divided by the watts of electricity over an entire cooling season. The minimum SEER rating a system can currently have under current guidelines is 13. The higher the SEER rating, the more energy efficient a system will be and the more money you will save on your electric bills.
Self-contained System
A package unit.
Sensible Heat
Heat added or subtracted that causes a change in temperature.
Sensor
A device that reacts to a change in conditions.
Single-Speed
A single-speed motor runs at top speed until it satisfies your temperature setting and then shuts off. They’re generally louder at start-up, consume more energy than alternative motor types and can cause more stress on mechanical parts.
Split System
An outdoor unit combined with an indoor unit (as opposed to a package unit), generally providing more efficiency and configuration options.
Thermostat
A wall mounted device that monitor and controls the output of an HVAC system.
Thermostatic Expansion Valve (TXV)
A device that creates a constant evaporator temperature by regulation of refrigerant flow through the system.
Ton
One ton is 12,000 BTUs per hour.
Tonnage
This is a measure of the cooling capacity of the air conditioner. One ton of cooling is equal to 12,000 BTU/hour. BTU, or British Thermal Unit, is a measure of energy. It is the amount of energy needed to raise one pound of water by one degree Fahrenheit. It is used to measure how much heat the air conditioner can remove. If you are not sure of the tonnage you need, have one of our trusted professionals help you today!
Upflow Furnace
A furnace that pulls in air from the bottom and releases it through the top.
Two-Speed
The base required for a high-efficiency air conditioner, two-speed motors cycle on in low gear and attempts to satisfy the cooling load for the home, shifting to high gear if necessary. Once it reaches the desired temperature, it cycles back down to low before shutting off. With just two speeds, it reduces start-up noise, operates with greater energy efficiency and causes less stress on mechanical parts compared to single-speed motors.
Variable-Speed
Ideal for high-efficiency air conditioners, a variable-speed motor functions much like a two speed, only with several speeds of operation. When compared with single- or two-speed motors, it facilitates smoother cycling and more precise performance control, as well as the most-quiet operation, highest energy efficiency and least stress on mechanical parts.
Ventilation
The process of moving air (changing) into and out of an interior space either by mechanically induced (forced) means.
Volt
Is the derived unit for electrical potential and electromotive force.
Voltage
The force pushing electrical current along wires and cables.