BASIC WORD LIST FOR HVAC SYSTEMS
[Diagram]
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Actuator:
A device that changes the position of moveable components such as valves or dampers.
Air Filter:
A device used for removing small particles from the air.Filters come in all sizes and there are many different types, efficiencies and qualities of filters.
Air Handler:
Anything that moves the air such as fans, blowers, etc. When we use the term “air handler”, we usually mean the whole air handling unit including the blower, heating and cooling elements, filter racks or chamber, dampers, but not including the ductwork throughout the building.
Air Conditioner:
Device used to control temperature, humidity, cleanliness and movement of air for an area of a building. The term is often used in relation to “cooling” only, but it really refers to heating and humidity control as well.
Air Conditioning (A/C) System:
System, consisting of all the components, including the ducts, fan, heating and cooling elements, filters, thermostat and other parts that control temperature, humidity, cleanliness and movement of air for an area of a building.
Aluminum Flex:
A type of air duct made of a flexible aluminum. It has many little ridges in a circular pattern around the duct.
Blower:
A device with blades – also called a fan – which moves air by pushing or pulling it in a desired direction.
Boiler:
A closed container wherein a liquid may be heated and is sometimes vaporized. Hot water is often used in the coils of larger A/C systems to heat air. The water is heated in a separate boiler, then piped to the unit through the coils and returned to the boiler to be re-heated.
Burner:
A device, such as the heating element of a gas stove or furnace, where the burning of fuel takes place. Gas furnaces have burners that heat the heat exchanger which then in turn heats the air passing over it. The burnt gas fumes never enter the air stream that supplies the rooms with warm air. The gas fumes are always vented outside the house or building through an exhaust vent or flue.
Carbon Monoxide:
A colorless, odorless and poisonous gas produced when natural gases (and other types of fuels) are burned. Safely removing this substance is one of the reasons that the gas fumes from a burner are vented outside of the home or building.
Central Heating System:
A self -contained furnace system that supplies heated air through ducts to spaces remote from the furnace location.
CFM:
Cubic Feet per Minute. With regard to Air Conditioning, refers to the cubic feet of air per minute moved or handled by the A/C unit, blower or exhaust system.
Chiller:
A heat transfer device used in large building A/C systems that removes heat from the building through a condensing process.
Circuit:
The path on which an electrical current may flow from its source through the whole route or circuit and back to the source. When the circuit is whole, electricity can flow. In a home or building, there are many electrical circuits that supply various parts of the structure with electricity. Some circuits are designated for just one machine, such as a computer, or one room. The furnace or A/C system usually has its own circuit.
Circuit Breaker:
A safety device which automatically opens a circuit (meaning that the circuit is no longer whole so electricity can no longer flow through that circuit), when the circuit is overloaded, or too much demand is put on that circuit. Without the circuit breaker, a circuit could be overloaded to the point of serious damage or a fire. The circuit breakers are in a box and are switches which can be re-set when they have "tripped" or opened as described above.
Coils:
A series of connected pipes or tubing arranged in a coil or a row, used to carry hot or cold water, refrigerant (Freon) or other liquid to heat or cool air in an air conditioning unit. Attached to the tubing are a series of thin copper or aluminum fins that transfer the heat or cold from the liquid contained in the tubes to the air passing over the fins. The coils resemble the radiator of an automobile.
Compressor:
A machine which compresses or squeezes together or into a smaller space, any gas, liquid, air, etc. In an A/C system, the compressor draws the refrigerant (Freon, etc.) from the system and compresses or squeezes it into the condenser.
Condensation:
Liquid or droplets that form when a gas is cooled to below the point that it turns into a liquid. When the A/C unit is working, some of the water vapor in the air passing through the system cools to the point that it turns into a liquid, thus condensation is formed, especially on the cooling coils.
Condensation Pan:
Sometimes called a "drip pan." A trough or pan used to collect or trap the condensation formed on the evaporator coils when an A/C system is operating. This water then drains out through a pipe or is pumped outside.
Condenser:
Condense means to change from a gas into a liquid. The condenser is that portion of an A/C system that changes the gaseous warm refrigerant (like Freon) fluid back into a cold liquid.
Condenser Coils:
The coils through which the refrigerant is condensed back into a liquid. The condenser coils are usually located or exposed to the outside air. Heat is given off when the refrigerant (freon) is condensed, so it can change into a liquid.
Cooling Tower:
Heat-transfer device, a structure looking like a tower, located outside, in which atmospheric air cools warm water that comes from a cooling coil somewhere inside the building’s A/C system. Used in large buildings.
Damper:
A device for controlling the volume of airflow. Usually a moveable metal plate or flap on the interior of an air handler or air duct. When it is used as part of a register (grille or diffuser), it is built with a series of adjustable flaps, louvers or fins.
Dehumidifier:
A device that removes moisture from the air.
Diffuser:
A type of grille that distributes air by spreading it out through its louvers which are usually pointed in different directions.
Drip Pan:
See “Condensation Pan”
Duct:
A tube, pipe or passageway for carrying the air from one point to another. Ducts come in all sizes, shapes and are made from a number of different materials, the most usual being galvanized steel.
Duct Board:
Also called “Fiber Board”. A type of duct made of fiberglass insulation compressed and glued to make it more rigid. It has a foil exterior, except when in a round form.
Economizer:
A device, usually found in the OSA that increases or decreases the amount of outside air intake in order to conserve energy.
Evaporation:
The process of changing of a liquid into a gas. This occurs in the evaporator coils. When the refrigerant changes from a liquid to a gas it absorbs heat from the air passing through the coil via the evaporator coils.
Evaporator Coils:
The set of coils that cool the air in an A/C system, and in which the refrigerant evaporates back into a gas. When the refrigerant evaporates, it absorbs heat from the air passing through the coils.
Exhaust:
Refers to any system (duct, grilles, blower or fan) which pulls air out of a room or an area and doesn't return it to be reheated or cooled, but just removes the air to the outside of the building.
Extractor:
A device usually located in the main trunks of a duct system. It is a scoop type affair and looks like a small turning vane located at the side of the main duct. Its purpose is to turn or extract air from a main duct and direct it into a smaller duct or out of a register.
Fan/Coil Unit:
An A/C unit that contains a fan and a coil and/or heat exchanger for cooling and/or heating, in the same casing. The condensing coils are separate. Usually found hanging in the attic, in a closet, built into a wall or inside an air duct.
Fiber Board:
See Duct Board
Fiberglass:
Literally, glass fibers. A special form of very fine fibrous glass. For our purposes, usually used as an insulation in several different forms - loose, as in attic insulation, a wrapping to go around ducts or a liner inside ducts or A/C units.
Fin:
A very thin, flat projection from the coil piping usually made of aluminum or copper. These are used to transfer the heat or cool more rapidly from the coil piping to the air passing through.
Flex Duct:
A type of flexible ducting usually made of plastic, a spiraled wire and fiberglass. The inner lining is made of clear plastic, next is a spiral wire to reinforce it to prevent it from collapsing (the wire looks like a "slinky"). Over that is wrapped a layer of fiberglass insulation and the outer layer is usually blue-gray or black plastic or a type of aluminum foil membrane. A similar type duct called "End Flex" or metal flex uses a flexible coil of Aluminum as the inner liner and duct reinforcement. Also see “Aluminum Flex”.
Foil-Back Insulation:
Type of fiberglass insulation found in attics or wrapped around the exterior of ducts that has a foil covering facing towards the inside of the space.
Freon:
A brand name of a refrigerant fluid used in A/C systems that is no longer used in new systems.
Furnace:
That part of the heating system where combustion and the heat transfer process takes place.
Fuse:
An electrical safety device usually made of a soft metal which is supposed to melt when a circuit is overloaded.
Galvanize:
A process used to apply a coating of zinc to metal to make it rust-resistant.
Grille:
An open louvered or ornamental structure or screen covering the end of an air passageway. Note: The names "grille," "vent," "diffuser" and "register" are often used interchangeably.
Heat Exchanger:
A device used to transfer heat from a warm or hot surface to a cold or cooler surface. In a furnace, cool air picks up heat as it passes over the heat exchanger and then is distributed by the ductwork to the rooms to be heated.
Heat Pump System:
This type of system heats a temperature-controlled space by reversing the usual cycle of an A/C system. The usual cycle is to transfer heat from a building by an evaporation of the refrigerant in the coil (absorbing heat) located inside the air handler and then compression of the refrigerant at the condenser coil, located outside the building, thereby releasing the heat.
With a Heat Pump System, the compression takes place inside the coils in the air handler and heat is released into the air passing through the coils and into the conditioned space. This cycle can also be reversed so the conditioned space's air can be cooled.
Humidifier:
A device that adds moisture to the air.
Insulation:
A material or substance used to keep a surface from losing or transferring heat or electricity. Rubber is a good insulation for electrical. Fiberglass is a common insulation for A/C systems. Asbestos was also used until the early 1980’s.
Linkage:
Connecting rods that attach the dampers to the actuator that transfer the motion from the actuator to the dampers, making them open or close.
Louver:
A flap or fin used to control and direct the flow of air.
Lined Duct:
This type of duct, round, square or rectangular has fiberglass insulation fastened to its interior for insulation or noise dampening purposes.
Machine Room:
Also called a “Mechanical Room”. A room, usually in a larger building which contains the air conditioning equipment.
Mixing Box:
Compartment into which two air supplies are directed and then mixed together before being discharge. Usually part of a “Dual or Double Duct A/C System”.
OSA (Outside Supply Air):
Refers to the part of an A/C system which supplies the system with fresh air or Outside Supply Air which replaces the stale air inside the building.
Package Unit:This is an air-handling unit that comes as a "package." The condenser coils, compressor, blower and evaporator coils are all mounted in the same cabinet which is usually found on a rooftop.
Pilot Light:
A small flame in a gas furnace kept burning all the time used to light the main burner whenever the main burner is turned on.
Plenum:
A chamber for moving air under slightly positive pressure, meaning there is a higher pressure inside the chamber than outside. This positive pressure causes the air to move from the plenum into the next chamber or area. In an air conditioning system, there is usually a return plenum just before the unit and a supply plenum just after the unit. The supply ducts distribute off the supply plenum.
Preheat Coil:
Heating coil installed upstream of cooling coil, or at the front of an air-handling system to preheat air.
PSI - Pounds per Square Inch:
The air pressure inside an "air movement system" is measured in PSI.
Refrigerant:
Substance used in a cooling device, such as an Air Conditioner. It absorbs heat in the evaporator coils and changes from a liquid to a gas, and releases its heat in the condenser as it returns from a gas to a liquid. “Freon” is a brand name of a refrigerant.
Register:
A grille and damper combination that covers an end of an air duct. Can be supply, return or exhaust. The damper is used to control the volume of air passing through the grille; and the grille covers the opening.
Note: The names "grille," "vent," "diffuser" and "register" are often used interchangeably.
Reheat Coil:
Heating coil installed downstream of cooling coil.
Return:
Refers to any duct, register, blower, fan or portion of an air handler returning the air from the building to the unit to be conditioned (heated or cooled).
Sensor:
An instrument designed to detect and measure a variable, such as temperature, air pressure, humidity or airflow.
Spiral Duct:
A type of round or elliptical metal duct which has a joint or ridge running spirally along its length.
Split System:
As opposed to Package Unit system. An A/C system in which the condenser is outside and away from the air handler and the evaporator coil (that are located inside).
Supply:
Refers to any duct, register, grille, blower, fan or component that pushes or supplies the building or room with air.
Swamp or Evaporative Cooler:
Type of cooler that cools by the evaporation of water as air is drawn through a water-soaked pad. Commonly found in restaurants, older homes and some industrial buildings. Usually situated on a rooftop.
Terminal Device:
A collective term for grilles, registers and diffusers, and also VAV boxes.
Thermostat:
A device in the air-conditioned space which senses the temperature and acts as a control to bring in hot or cold air.
Timer:
A clock device that starts and stops an "air movement system" on a regular schedule.
Ton:
Refers to the cooling capacity of a refrigeration system. A one ton system could melt 1 ton of ice in a 24-hour period via its heat transfer capacity.
Turning Vanes:
Metal blades, usually curved, installed inside a duct or air-handler, used to direct the flow of air around a corner or in a certain direction.
Valve:
A device to regulate or stop the flow of fluid in a pipe or a duct.
VAV System:
(Variable Air Volume) An A/C system using varying air flow to control the condition of air, as opposed to the use of constant airflow with varying temperature.
VAV Box:
Device connected in-line to the duct system containing a damper to control the volume of airflow. A thermostat controls the action of the box.
Ventilation:
Process of supplying or removing air that may not have been conditioned.
Zone:
Each area served by a particular thermostat is usually referred to as a “Zone”.
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