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Glossary

  • A-Coil

    A heat exchanger consisting of two diagonal coils that are joined together in the shape of the letter A.

  • AC

    Alternating Current - A type of current where the polarity is perpetually reversing, causing the directional flow in a circuit to reverse at regular intervals.

  • ACCA

    Air Conditioning Contractors of America

  • Accumulator

    A storage tank located in the suction line of a compressor.

  • ACH

    Air Changes per Hour

  • Acid Condition

    The presence of corrosive substances in a sealed refrigeration system.

  • Activated Carbon

    Granular processed carbon, commonly used in air filter media to clean the air.

  • Active Cooling

    The use of compressor equipment to cool and dehumidify the air.

  • Add On Heat Pump

    Dual fuel system - Installing a heat pump with an existing fossil fuel furnace.

  • Advanced Reciprocating Compressor

    Type of compressor that uses a more efficient process for compressing refrigerant for better cooling efficiency.

  • AFUE

    Annual Fuel Utilization Efficiency - an efficiency rating for furnaces and gas heating equipment.

  • AHU

    Air Handler Unit - The inside part of the A/C system.

  • Air Balancing

    The adjustments made to an air conditioning and/or heating system to deliver the correct amount of airflow to each room.

  • Air Change

    The amount of air required to completely replace the air in a room or building not to be confused with re-circulated air.

  • Air Conditioner

    Equipment used to control indoor air temperature, relative humidity, purity, and movement.

  • Air Conditioning

    Making indoor air more comfortable by transferring heat and humidity to the outside air.

  • Air Diffuser

    Air distribution outlet or grille designed to direct airflow into desired patterns.

  • Air Duct

    Pipes that carry warm air and cold air to rooms and back to furnace or air conditioning system.

  • Air Exchange Rate

    The rate at which outside air replaces indoor air in a space.

  • Air filter

    In HVAC - the media, element, or device used to remove unwanted particles, vapors, or odors from indoor air.

  • Air Flow

    The distribution or movement of air.

  • Air Handler

    The inside part of the A/C system that contains the blower, evaporator coil, and heater. Also called AHU or Air Handling Unit.

  • Air infiltration

    The unwanted entry of air into a building.

  • Air Pressure Control

    Air Pressure Switch - Used to detect air pressure drop across the coil in a heat pump outdoor unit due to ice buildup.

  • Air source

    The use of ambient air as the heat source or heat sink with heat pumps.

  • Air Vent

    A general term that describes the port where air enters (or exits) a duct, room or area.

  • Air-Cooled

    Using a fan to move heat away from the condenser coil to the outside air.

  • Air-cooled Condenser

    a heat exchanger that transfers heat into the surrounding air

  • Allergen

    A substance capable of causing an allergic reaction because of an individual’s sensitivity to that substance

  • Alternating Current

    A type of current where the polarity is perpetually reversing, causing the directional flow in a circuit to reverse at regular intervals.

  • Aluminum Fin

    Attached to a sleeve around the coil and used to dissipate heat away from the coil.

  • Ambient Temperature

    The temperature of the air surrounding HVAC equipment.

  • Amperage

    The rate of electrical current flow in a circuit.

  • ARI

    Air Conditioning and Refrigeration Institute

  • ASHRAE

    American Society of Heating Refrigeration and Air Conditioning

  • Balance Point

    When the building's heat output equals the heat input.

  • Blower coil

    Another term for evaporator coil

  • Boiler

    A sealed chamber in which water is boiled and converted to steam for the purpose of supplying steam generated heat and hot water.

  • Boiling Point

    The temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid causing the liquid to change into a vapor.

  • Boot

    A fitting that connects round to rectangular sheet metal or fabricated duct systems.

  • Breaker

    A heat-activated electrical device used to open an electrical circuit to protect it from excessive current flow.

  • BTU

    British Thermal Unit - a standard unit of measure of heat used in heating and air conditioning

  • BTUh

    British Thermal Units per hour - one ton of cooling capacity equals 12,000 BTUh

  • Burner

    device that facilitates the combustion of air and gas

  • Burner Orifice

    The opening in the burner through which the gas or fuel passes prior to combustion.

  • Capacity

    ability of a cooling or heating system to cool or heat a specific amount of space

  • Carbon Monoxide

    (CO) - A colorless, odorless, and highly toxic gas produced when carbon-containing fuels are burned.

  • Ceiling Plenum

    a space provided for the circulation of air - typically between the structural ceiling and the drop ceiling or under a raised floor.

  • Celsius

    A temperature scale that registers the freezing point of water as 0° and the boiling point as 100° under normal atmospheric pressure.

  • Central Air

    Central Air Conditioning System - a system in which indoor air is cooled and dehumidified at a central location.

  • Centrifugal Compressor

    A compressor in which compression is obtained by radial acceleration.

  • CFC

    Abbreviation for chlorofluorocarbons

  • CFM

    Cubic Feet per Minute - a standard of airflow measurement

  • Charge

    amount of refrigerant in a system

  • Chase

    a groove in a masonry wall or through a floor to accommodate pipes or ducts

  • Chimney

    A vent for the products of combustion - flue

  • Chlorofluorocarbons

    A class of gaseous compounds containing carbon, chlorine, and fluorine (and sometimes hydrogen) - gases used in refrigerants, cleaning solvents and aerosol propellants. Believed to deplete the ozone.

  • Coefficient of Performance

    COP or CP - the ratio between useful energy acquired and energy applied
    the basic parameter used to report efficiency of refrigerant based systems

  • Compression Ratio

    the ratio determined by dividing the discharge pressure, in PSI, by the suction pressure in PSI

  • Compressor

    A mechanical device used to pressurize refrigerant gas for the purpose of circulating refrigerant.

  • Condensate

    the product of the transition of a gaseous substance into a liquid state caused by a drop in pressure or temperature.

  • Condensate Pan

    Drip Pan - The tray or pan used to collect water as it condenses from the evaporator

  • Condensate Pump

    a water pump that disposes of or re-circulates collected condensate

  • Condenser

    The outside unit of an air conditioning or heating system where the refrigerant condenses from a gas to a liquid and hot or cold air from the building is released outside the conditioned space.

  • Condenser Coil

    Part of the outdoor portion of an air conditioner or heat pump that releases heat in the summer and (in a heat pump) collects heat in the winter.

  • Condenser Fan

    the fan in the outside unit that circulates air over the air-cooled condenser to change the refrigerant vapor into a liquid

  • Condensing Furnace

    a high-efficiency, gas forced-air furnace that uses a second condensing heat exchanger to extract the latent heat in the flue gas

  • Condensing Temperature

    the temperature at which a gas or vapor will condenses into liquid

  • Condensing Unit

    a. a complete unit that includes the compressor and the condensing coil;
    b. part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control.

  • Conditioned Air

    Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the “comfort zone”

  • Contactor

    a switch that can repeatedly cycle, making and breaking an electrical circuit

  • Convertible Air Handler

    an air handler that can be installed in either an up flow or a horizontal left configuration

  • Cooling Capacity

    the rate heat is removed from a space under standard conditions

  • Cooling Coil

    another term for evaporator coil - part of the air conditioner or heat pump that is located inside the air handler or attached to the furnace.

  • Cooling Load

    the amount of heat energy that would need to be removed from a space to maintain the temperature in an acceptable range

  • Copper Coil

    Coils move refrigerant under high pressure and copper is known for its durability and efficient heat transfer

  • CSA

    Canadian Standards Association

  • CUL

    Canadian mark for Underwriters Laboratories Inc.

  • Damper

    A movable plate in ductwork that can be opened and closed to modulate airflow.

  • Data Plate

    An equipment identification label; usually lists model and serial numbers and various unit ratings

  • DC

    Direct Current - an electrical current that only flows in one direction

  • Decibel

    (abbreviated dB) is the unit used to measure the intensity of a sound

  • Degree-day

    a measure of departure from the mean daily temperature.

  • Dehumidification

    Dehumidification is the process in which the moisture (water vapor or humidity) is removed from the air keeping its dry bulb temperature (DBT) constant

  • Dehumidifier

    a device used to remove moisture from indoor air

  • Dehumidify

    to remove moisture from indoor air

  • Direct Vent

    pulls outside air for combustion and vents combustion gases directly outside

  • Disconnect Box

    a switch box that cuts off electrical power to a machine being serviced

  • DOE

    Department of Energy

  • Down Flow Furnace

    a type of furnace that takes in air at its top and discharges air at the bottom

  • Drip Pan

    the tray or pan used to collect water as it condenses from the evaporator

  • Duct

    the conduits that carry cooled, warmed, or ventilated air from the air conditioning system or furnace to the rooms and back

  • Ductless Air Conditioning

    mini split-system air conditioners - air conditioning system with no ductwork

  • Ductless Heat Pump

    ductless, mini-split heat pump – a heat pump system with no ductwork

  • Ductwork

    a branching network of tubes used to circulate air throughout a building

  • EER

    Energy Efficiency Ratio

  • Effective Temperature

    the overall or net effect of the air temperature on a person; the relative humidity, and movement of air

  • Efficiency

    a general term used to describe the ratio of output of a device, appliance, system or activity, to the input necessary to create that output.

  • Electric Heating

    electrical equipment that converts electric current to heat by means of resistors that emit radiant energy

  • Electronic Air Cleaner

    An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate

  • Electrostatic Filter

    a filter device for cleaning or purifying the air that employs electricity to charge plates and attract dust particles

  • Energy Audit

    an assessment to measure the current energy consumption for a house, building, or indoor area

  • Energy Recovery Ventilator

    ERV - Like an HRV, an ERV uses exhaust air to preheat or precool the supply air but it also captures the humidity in the air and keeps it on the same side of the system it came from.

  • Energy Saver Switch

    an energy-saver switch that causes the air conditioner's fan and compressor to cycle on and off together, reducing energy use

  • Energy Star®

    a government sponsored brand used to identify energy efficient appliances or products. The trademark was developed by the US Department of Energy (DOE) and the US Environmental Protection Agency (EPA)

  • Envelope

    In air conditioning and heating, a term used to describe the condition of the parts of a home or building that interact with outside air.

  • ERV

    ERV - Like an HRV, an ERV uses exhaust air to preheat or precool the supply air but it also captures the humidity in the air and keeps it on the same side of the system it came from.

  • Evaporator Coil

    Also referred to as blower coil, cooling coil or indoor coil.
    Part of the inside unit - a network of tubes filled with refrigerant that removes heat and moisture from the air as the refrigerant evaporates into a gas again.

  • Fan Coil

    An indoor component of an air conditioner or heat pump system, used in place of a furnace and evaporator coil, to provide change the refrigerant from a gas to a liquid (or vice-versa) and blow air over the coil to cool or heat your home

  • Field Matching

    a term used to describe the addition of new components to older equipment in an air conditioning and heating system.

  • Flexible Duct

    a type of air duct material, often continuous, that is easy to route around obstacles in attics, etc, by bending it gently

  • Flue

    a pipe that vents combustion gases to the outside air, usually through convection

  • Forced Air

    A term to describe a system for heating, air conditioning, ventilation (or a combination of these) that uses a fan or blower to move or “force” air through the system and into the intended rooms

  • Forced-Air Heating System

    heat is produced in a centralized area, then distributed through a network of ducts

  • Freon

    A brand name of refrigerant manufactured by the DuPont Company

  • Furnace

    a self-contained heating unit designed to deliver heated air to a home or building

  • GAMA

    Gas Appliance Manufacturing Association

  • GAP™ Technology

    a patented technology in which UVGI lamps are used to activate a photocatalyst producing hydroxyl radicals; an extremely effective method for removing biologics from the air stream.

  • Ground Source

    the use of ground or soil below the frost line as the heat source or heat sink for a heat pump

  • Ground Source Heat Pump

    GHP or geothermal heat pump - a heat pump that uses the earth as a heat source during the winter and as a heat sink during the summer

  • Ground Water-Source

    the use of water from an underground well as the heat source or heat sink for a heat pump

  • HCFC

    abbreviation for hydro chlorofluorocarbons

  • Heat Exchanger

    a. major part of a furnace that transfers heat created in the fuel combustion area to the surrounding air that is pumped into the rooms;
    b. condenser or evaporator device

  • Heat Gain

    the heat that enters conditioned space by infiltration from outside air, solar radiation, human respiration, lighting devices, etc

  • Heat Loss

    the rate of heat transfer from a heated space to the outdoors

  • Heat Pump

    a type of mechanical compression cycle refrigeration system capable of heating

  • Heat Recovery Ventilator

    HRV - a system that uses exhaust air to preheat or precool the supply air

  • Heat Transfer

    the movement of heat energy from one place to another

  • Heating Coil

    a general term for a coil device that serves as a heat source

  • Heating, Ventilation, and Air Conditioning

    HVAC - Control of the indoor environment (temperature, humidity, airflow, and air filtering) of a building

  • HFC

    hydroflorocarbon - refrigerant

  • Horizontal Flow

    a type of furnace, installed on its "side” that draws in air from one side, heats it, and sends the warm air out the other side

  • HRV

    Heat Recovery Ventilator - a system that uses exhaust air to preheat or precool the supply air

  • HSPF

    Heating Seasonal Performance Factor - measure of heating efficiency for air source heat pumps

  • Humidifier

    a device that adds water vapor to the indoor air to increase humidity

  • Humidistat

    a type of indoor comfort control device that senses humidity and cycles a humidifier on and off

  • Humidity

    the amount of water vapor in the atmosphere

  • HVAC

    heating, ventilation, and air conditioning - the technology of indoor environmental comfort

  • HVAC Excellence

    a not-for-profit organization, created in 1994 to improve the future and current technical workforce’s competency through quality education

  • Hybrid Heat

    a duel fuel system that combines an electric heat pump with a furnace

  • IAP

    Indoor air pollution - including carbon monoxide, formaldehyde, pesticides, solvents, fragrance, cleaners, bacteria, viruses, mold, pet dander, dust

  • IAQ

    Indoor Air Quality - An overall measure of temperature, humidity, chemical pollutants, biological contaminants, movement and sensory qualities of indoor air.

  • Indoor Air Quality

    IAQ - An overall measure of temperature, humidity, chemical pollutants, biological contaminants, movement and sensory qualities of indoor air.

  • Indoor Coil

    Also referred to as blower coil, cooling coil or indoor coil.
    Part of the inside unit - a network of tubes filled with refrigerant that removes heat and moisture from the air as the refrigerant evaporates into a gas again.

  • Insulation

    As it applies to air conditioning and heating, any material that slows down the transfer of heat

  • Ion

    An electrically charged atom or group of atoms that has lost or gained electrons

  • Kilowatt

    a measure of 1,000 watts of electrical power

  • Kilowatt-hour

    A common unit of electrical consumption. It is the equivalent of one kilowatt (1 kW) of power expended for one hour (1 h)

  • kWh

    kilowatt-hour - A common unit of electrical consumption. It is the equivalent of one kilowatt (1 kW) of power expended for one hour (1 h)

  • Latent Heat

    the heat required to convert a solid into a liquid or vapor, or a liquid into a vapor, without change of temperature.

  • Lift Gate

    a hydraulic platform attached to the back of some freight trucks; raises and lowers from ground level to truck level for loading and unloading heavy freight.

  • Load

    a.  the amount of heating or cooling a system needs to produce for indoor comfort
    b.  the electrical energy consumed by a component
    c.  circuit, device or equipment connected to a source

  • Load Calculation

    A computation of the quantity of cooling and heating (in BTUs) an air conditioning and heating system must produce for indoor comfort.

  • Load Estimate

    studies to determine the heating or cooling requirements of a home or building

  • Low Boy

    a type of furnace configuration in which the furnace is lower in height and occupies more floor space

  • Manual D®

    A trademark of the American Air Conditioning Contractors of America (ACCA). This publication covers the proper design, installation, maintenance, and repair of ductwork.

  • Manual J®

    ACCA method for calculating heating and cooling load for residential buildings

  • Manual RS®

    A trademarked ACCA publication covering the design, installation, and commissioning of a residential HVAC system.

  • Matched System

    A heating and air conditioning system comprised of components that have been certified to perform at specific comfort and efficiency levels when used together and according to design and engineered specifications

  • Media

    as used in air conditioning and heating, the material in an air filter that traps and holds the impurities until it is cleaned or replaced

  • MERV

    The Minimum Efficiency Reporting Value - the measure of the efficiency of an air filter

  • NATE

    North American Technician Excellence - this is the nonprofit organization that tests and certifies technicians in heating, ventilation, air conditioning, and refrigeration

  • OEM

    Original Equipment Manufacturer- generally used in contrast with aftermarket, or equipment produced by someone other than the original

  • Operating Cost

    the day-to-day cost of running your home comfort equipment, based on energy use

  • Outdoor Coil

    Condenser Coil - Part of the outdoor portion of an air conditioner or heat pump that releases heat in the summer and (in a heat pump) collects heat in the winter.

  • Packaged Unit

    Packaged air conditioner, packaged heat pump - a central forced-air system that has the condensing and air handling components in a single cabinet.

  • Payback Analysis

    the study and calculation of the number of months or years required for the monthly operating savings from a new air conditioning and heating system to offset its purchase price.

  • Payback Period

    number of months or years required for the operating savings from a new air conditioning and heating system to offset its purchase price

  • PCP

    Photocatalytic Compound Panel created by Genesis Air

  • Photocatalytic Oxidation

    PCO - a chemical reaction influenced or initiated by light that removes electrons from a catalyst and adds those electrons to a compound.

  • PMA

    Planned Maintenance Agreement -- these are agreements offered by HVAC contractors that set a certain number of maintenance visits per year, usually for a discounted fee.

  • Programmable Thermostat

  • Puron

    R-410a refrigerant - 50/50 blend of R-32 and R-125; an earth friendly replacement for R-22

  • QuieTech™

    a noise reduction system that provides comfortable heat while generating very little noise in the process

  • R-22

    HCFC-22 – a refrigerant marketed for more than 40 years which has been found to contribute to the depletion of the ozone.

  • R-410A

    a refrigerant used in residential and light commercial air conditioning and heat pump systems; first marketed in 1996 as a replacement for R-22 (Freon).

  • R-factor

    a rating of insulating or thermal resistance value

  • Radiant Barrier

    a layer of thin material usually made of metallic foil that reflects heat in a specific direction.

  • Radiant Floor Heating

    the use of embedded tubing within concrete floors through which hot water is pumped for heating the floor and space around it

  • Reciprocating Compressor

    a type of compressor that uses a piston cylinder mechanism to provide its pumping action

  • Refrigerant

    a chemical compound used for cooling applications, such as refrigerators and air conditioners, capable of absorbing heat at low temperatures and releasing heat at higher temperatures

  • Refrigerant Charge

    the amount of refrigerant required to be in an air conditioning or refrigeration system

  • Refrigerant Lines

    Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil

  • Refrigeration Capacity

    a measure of the effective cooling capacity, expressed in Btu per hour or in tons.

  • Relative Humidity

    the amount of moisture in the air compared to the maximum amount of moisture the air can hold at that temperature, expressed as a percentage

  • Return Side

    The path of air as it goes to the air-handler or furnace so it can be cooled or heated

  • Reversing Valve

    a type of valve, used by heat pumps to change the direction of refrigerant flow allowing the heat pump refrigeration cycle to change from cooling to heating (and vice versa).

  • Rotary Screw Compressor

    a type of compressor that employs two meshed rotating positive-displacement helical screws to force the gas to move.

  • Scroll Compressor

    a compressor that uses two spiral-shaped scrolls to pump or compress liquids and gases

  • SEER

    Seasonal Energy Efficiency Ratio - a rating of the efficiency of air conditioner or heat pump.

  • Sensible Heat

    heat that causes a change in temperature in an object or system without change in volume or pressure

  • Sick Building Syndrome

    A combination of problems and complaints about indoor building environments and related human health issues.

  • Single Package

    A central air conditioner unit that contains both the condenser and air handling components in one packaged unit.

  • Sound Rating Number

    A unit of sound based on ARI standard tests for air conditioners and heat pumps.

  • Source Temperature

    the temperature of the medium from which a refrigeration system extracts its heat

  • Space Heater

    a self-contained appliance for heating an enclosed room

  • Specific Humidity

    the weight of water vapor, per unit weight of dry air

  • Split System

    air conditioning system made up of an outdoor unit, which contains the condenser and compressor, and an indoor unit, which is often connected to a furnace.

  • SRN

    A unit of sound based on ARI standard tests for air conditioners and heat pumps.

  • Static Pressure

    condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.

  • Supply Side

    The part of an air conditioning and heating system that moves the conditioned air from the air handler or furnace to the rooms.

  • Tankless Water Heater

    a water heater that heats water directly, as needed, without the use of a storage tank

  • Temperature Zones

    individual spaces in an HVAC system in which temperature is controlled seperately

  • Thermostat

    Control devices that consist of a series of sensors and relays that monitor and activate the functions of an air conditioning and heating system.

  • Thermostatic Expansion Valve

    TXV - a precision device used to meter the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator.

  • Ton

    the unit of measurement for capacity of air conditioning systems. One ton of air conditioning removes 12,000 BTUs of heat per hour.

  • Two-stage

    equipment that operates at more than one speed.

  • Up Flow Furnace

    a type of heating unit in which air is drawn in through the sides or bottom and the warm air is discharged at the top

  • Variable-speed motor

    a type motor that runs at a wide range of speeds

  • Vent

    an opening that allows air, gas, or liquid to pass out of or into a confined space

  • Ventilation

    the circulation of air throughout a building

  • Ventilator

    a mechanical device that captures heating or cooling energy from exhaust air and transfers it to fresh incoming air

  • Water-cooled Condenser

    a heat exchanger that transfers heat into water

  • Weather Stripping

    A material used to seal gaps around windows and exterior doors.

  • Weatherization

    In HVAC caulking and weather stripping to reduce air infiltration and exfiltration into/out of a building.

  • Whole House Approach

    A system plan for of indoor climate control and comfort that considers the interaction between humans, the structure, the building orientation, climate, and other elements or components

  • Window Air Conditioner

    A type of portable package air conditioning unit that fits in the window.

  • Zone

    a space in an air conditioning system with a separate temperature control.

  • Zoning System

    A single HVAC system that can meet different heating and cooling requirements for two or more areas, called “zones”.