HVAC systems use ventilation air ducts installed throughout a building that supply conditioned air to a room through rectangular or round outlet vents, called "diffusers"; and ducts that remove air through return-air "grilles"

Fire-resistance rated mechanical shaft with HVAC sheet metal ducting and copper piping, as well as "HOW" (Head-Of-Wall) joint between top of concrete block wall and underside of concrete slab, firestopped with ceramic fibre-based firestop caulking on top of rockwool. Ducts are used in heating ventilation and air conditioning ( HVAC) to deliver and remove air A fire-resistance rating typically means the duration for which a Passive fire protection System can withstand a standard fire resistance test. Sheet metal is simply Metal formed into thin and flat pieces It is one of the fundamental forms used in Metalworking, and can be cut and bent into a variety Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 A building joint is a junction where Building elements meet without applying a static load from one element to another Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag A firestop is a Passive fire protection System of various components used to seal openings and joints in fire-resistance rated wall Caulking is a process used to seal the seams in Wooden Boats or ships and riveted iron or steel ships in order to make them watertight Mineral wool, also known as mineral fibers or man-made mineral fibers are Fibers made from natural or synthetic Minerals or Metal

HVAC (pronounced either "H-V-A-C" or, occasionally, "H-vak") is an initialism or acronym that stands for "heating, ventilating, and air conditioning". Acronyms, initialisms, and alphabetisms are Abbreviations that are formed using the initial components in a phrase or name Acronyms, initialisms, and alphabetisms are Abbreviations that are formed using the initial components in a phrase or name Ventilation is the intentional movement of Air from outside a building to the inside The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort. HVAC is sometimes referred to as climate control and is particularly important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where humidity and temperature must all be closely regulated whilst maintaining safe and healthy conditions within. A skyscraper is a tall continuously habitable Building. There is no official definition or a precise cutoff height above which a building may clearly be classified as a skyscraper An aquarium (plural aquariums or aquaria) is a Vivarium consisting of at least one transparent side in which Water -dwelling Plants Sick building syndrome ( SBS) is a combination of ailments (a Syndrome) associated with an individual's place of work ( Office building) or residence In certain regions (e. g. , UK) the term "Building Services" is also used, but may also include plumbing and electrical systems. Refrigeration is sometimes added to the field's abbreviation as HVAC&R or HVACR, or ventilating is dropped as HACR (such as the designation of HACR-rated circuit breakers). Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable

Heating, ventilating, and air conditioning is based on the basic principles of thermodynamics, fluid mechanics, and heat transfer, and two inventions and discoveries made by Michael Faraday, Willis Carrier, Reuben Trane, James Joule, William Rankine, Sadi Carnot, and many others. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " Fluid mechanics is the study of how Fluids move and the Forces on them In thermal physics, heat transfer is the passage of Thermal energy from a hot to a colder body Michael Faraday, FRS ( September 22 1791 – August 25 1867) was an English Willis Haviland Carrier ( November 26, 1876 – October 7, 1950) was an Engineer and Inventor, and is known as the Reuben Nicholas Trane ( September 13, 1886 in La Crosse Wisconsin - September 5, 1954 in La Crosse founded Trane, the James Prescott Joule FRS (ˈdʒuːl December 24, 1818 &ndash October 11, 1889) was an English Physicist William John Macquorn Rankine FRS ( July 5, 1820 &ndash December 24, 1872) was a Scottish engineer and Nicolas Léonard Sadi Carnot (1 June 1796 &ndash 24 August 1832 was a French Physicist and Military engineer who in his 1824 Reflections The invention of the components of HVAC systems goes hand-in-hand with the industrial revolution, and new methods of modernization, higher efficiency, and system control are constantly introduced by companies and inventors all over the world.

The three functions of heating, ventilating, and air-conditioning are closely interrelated. All seek to provide thermal comfort, acceptable indoor air quality, and reasonable installation, operation, and maintenance costs. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55 Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure relationships between spaces. Ventilation is the intentional movement of Air from outside a building to the inside Infiltration is the unintentional or accidential introduction of outside air into a building typically through cracks in the building envelope and through use of doors for passage How air is delivered to, and removed from spaces is known as room air distribution. Characterizing how Air is introduced to flows through and is removed from spaces is called room air distribution. ^[1]

In modern buildings the design, installation, and control systems of these functions are integrated into one or more HVAC systems. A control system is a device or set of devices to manage command direct or regulate the behavior of other devices or systems For very small buildings, contractors normally "size" and select HVAC systems and equipment. For larger buildings where required by law, "building services" designers and engineers, such as mechanical, architectural, or building services engineers analyze, design, and specify the HVAC systems, and specialty mechanical contractors build and commission them. An engineer is a person professionally engaged in a field of Engineering. Mechanical Engineering is an Engineering discipline that involves the application of principles of physics for analysis Design, Manufacturing Architectural engineering, also known as Building Engineering, is the application of Engineering principles and Technology to Building Design Architectural engineering, also known as Building Engineering, is the application of Engineering principles and Technology to Building Design In all buildings, building permits and code-compliance inspections of the installations are the norm.

The HVAC industry is a worldwide enterprise, with career opportunities including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry had been historically regulated by the manufacturers of HVAC equipment, but Regulating and Standards organizations such as ASHRAE, SMACNA, ACCA, Uniform Mechanical Code, International Mechanical Code, and AMCA have been established to support the industry and encourage high standards and achievement. The American Society of Heating Refrigerating and Air Conditioning Engineers ( ASHRAE; pronounced 'ash'-'ray' is an international technical society for all individuals The Sheet Metal and Air Conditioning Contractors' National Association ( SMACNA; pronounced 'Smack'-'Nah' is an international association of HVAC contractors The Air Conditioning Contractors of America ( ACCA) is the largest HVAC contractor organization in the USA Designated as an American National Standard, the Uniform Mechanical Code (UMC is a model code developed by the International Association of Plumbing and Mechanical Officials The International Building Code (IBC is a Model building code developed by the International Code Council (ICC The Amateur Motorcycle Association (AMCA is a non-profit making governing body for off road motorcycling sport in the United Kingdom.

Heating

Heating systems may be classified as central or local. Central heating is often used in cold climates to heat private houses and public buildings. For the Grand Central Records albums see Central Heating (Grand Central album and Central Heating 2. Such a system contains a boiler, furnace, or heat pump to heat water, steam, or air, all in a central location such as a furnace room in a home or a mechanical room in a large building. A boiler is a closed vessel in which Water or other Fluid is heated A furnace is a device used for Heating The name derives from Latin fornax, Oven. A heat pump is a machine or device that moves Heat from one location (the 'source' to another location (the 'sink' or 'heat sink' using work. A furnace room is a room for locating the Furnace and auxiliary equipment A mechanical room or a boiler room is a room or space in a building dedicated to the mechanical equipment and its associated electrical equipment The system also contains either ductwork, for forced air systems, or piping to distribute a heated fluid and radiators to transfer this heat to the air. Radiators and convectors are types of Heat exchangers designed to transfer Thermal energy from one medium to another for the purpose of cooling The term radiator in this context is misleading since most heat transfer from the heat exchanger is by convection, not radiation. Convection in the most general terms refers to the movement of molecules within Fluids (i Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. The radiators may be mounted on walls or buried in the floor to give under-floor heat.

In boiler fed or radiant heating systems, all but the simplest systems have a pump to circulate the water and ensure an equal supply of heat to all the radiators. The heated water can also be fed through another (secondary) heat exchanger inside a storage cylinder to provide hot running water.

Forced air systems send heated air through ductwork. Ducts are used in heating ventilation and air conditioning ( HVAC) to deliver and remove air During warm weather the same ductwork can be used for air conditioning. The forced air can also be filtered or put through air cleaners.

Heating can also be provided from electric, or resistance heating using a filament that becomes hot when electricity is caused to pass through it. This type of heat can be found in electric baseboard heaters, portable electric heaters, and as backup or supplemental heating for heat pump (or reverse heating) system.

The heating elements (radiators or vents) should be located in the coldest part of the room, typically next to the windows to minimize condensation and offset the convective air current formed in the room due to the air next to the window becoming negatively buoyant due to the cold glass. Devices that direct vents away from windows to prevent "wasted" heat defeat this design intent. Cold air drafts can contribute significantly to subjectively feeling colder than the average room temperature. Therefore, it is important to control the air leaks from outside in addition to proper design of the heating system.

The invention of central heating is often credited to the ancient Romans, who installed a system of air ducts called "hypocaust" in the walls and floors of public baths and private villas. The Roman Empire was the post-Republican phase of the ancient Roman civilization, characterised by an autocratic form of government and large territorial A hypocaust (Latin hypocaustum) is an ancient Roman system of Central heating.

Ventilating

An air handling unit is used for the heating and cooling of air in a central location (click on image for legend). An air handler, or air handling unit (often abbreviated to AHU) is a device used to condition and circulate air as part of a heating ventilating and air-conditioning

Ventilating is the process of "changing" or replacing air in any space to control temperature or remove moisture, odors, smoke, heat, dust and airborne bacteria. Ventilation is the intentional movement of Air from outside a building to the inside Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants Methods for ventilating a building may be divided into mechanical/forced and natural types. ^[2] Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, and to keep interior building air circulating, to prevent stagnation of the interior air.

Mechanical or forced ventilation

"Mechanical" or "forced" ventilation is used to control indoor air quality. Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. However, in humid climates much energy is required to remove excess moisture from ventilation air.

Kitchens and bathrooms typically have mechanical exhaust to control odors and sometimes humidity. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. If the ducting for the fans traverse unheated space (e. g. , an attic), the ducting should be insulated as well to prevent condensation on the ducting. Direct drive fans are available for many applications, and can reduce maintenance needs.

Ceiling fans and table/floor fans circulate air within a room for the purpose of reducing the perceived temperature because of evaporation of perspiration on the skin of the occupants. A mechanical fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat ventilation, exhaust Because hot air rises, ceiling fans may be used to keep a room warmer in the winter by circulating the warm stratified air from the ceiling to the floor. Ceiling fans do not provide ventilation as defined as the introduction of outside air.

Natural ventilation

Natural ventilation is the ventilation of a building with outside air without the use of a fan or other mechanical system. Natural ventilation is the process of supplying and removing air through an indoor space by natural means It can be achieved with operable windows when the spaces to ventilate are small and the architecture permits. In more complex systems warm air in the building can be allowed to rise and flow out upper openings to the outside (stack effect) thus forcing cool outside air to be drawn into the building naturally through openings in the lower areas. Stack effect is the movement of air into and out of buildings Chimneys, Flue gas stacks, or other containers and is driven by Buoyancy. These systems use very little energy but care must be taken to ensure the occupants' comfort. In warm or humid months, in many climates, maintaining thermal comfort via solely natural ventilation may not be possible so conventional air conditioning systems are used as backups. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55 The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort. Air-side economizers perform the same function as natural ventilation, but use mechanical systems' fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate. Economizers, or in British English economisers, are mechanical devices intended to reduce energy consumption or to perform another useful function like preheating a Fluid

Air-conditioning

Air Conditioning and refrigeration are provided through the removal of heat. The definition of cold is the absence of heat and all air conditioning systems work on this basic principle. Heat can be removed through the process of radiation, convection, and conduction using mediums such as water, air, ice, and chemicals referred to as refrigerants. Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy Convection in the most general terms refers to the movement of molecules within Fluids (i Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter from a region of higher Temperature to a region of lower In order to remove heat from something, you simply need to provide a medium that is colder -- this is how all air conditioning and refrigeration systems work.

An air conditioning system, or a standalone air conditioner, provides cooling, ventilation, and humidity control for all or part of a house or building. The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort. An air conditioner is an Appliance, System, or mechanism designed to extract Heat from an area via a Refrigeration cycle The Freon or other refrigerant provides cooling through a process called the refrigeration cycle. Freon is DuPont 's trade name for its odorless colorless nonflammable and noncorrosive Chlorofluorocarbon and Hydrochlorofluorocarbon Refrigerants Thermodynamic heat pump and refrigeration cycles are the models for Heat pumps and Refrigerators. The refrigeration cycle consists of four essential elements to create a cooling effect. A compressor provides compression for the system. This compression causes the cooling vapor to heat up. The compressed vapor is then cooled by heat exchange with the outside air, so that the vapor condenses to a fluid, in the condenser. The fluid is then pumped to the inside of the building, where it enters an evaporator. In this evaporator, small spray nozzles spray the cooling fluid into a chamber, where the pressure drops and the fluid evaporates. Since the evaporation absorbs heat from the surroundings, the surroundings cool off, and thus the evaporator absorbs or adds heat to the system. Within a Downstream processing system several stages are used to further isolate and purify the desired product The vapor is then returned to the compressor. A metering device acts as a restriction in the system at the evaporator to ensure that the heat being absorbed by the system is absorbed at the proper rate.

Central, 'all-air' air conditioning systems are often installed in modern residences, offices, and public buildings, but are difficult to retrofit (install in a building that was not designed to receive it) because of the bulky air ducts required. A duct system must be carefully maintained to prevent the growth of pathogenic bacteria in the ducts. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have An alternative to large ducts to carry the needed air to heat or cool an area is the use of remote fan coils or split systems. These systems, although most often seen in residential applications, are gaining popularity in small commercial buildings. The coil is connected to a remote condenser unit using piping instead of ducts.

Dehumidification in an air conditioning system is provided by the evaporator. Since the evaporator operates at a temperature below dew point, moisture is collected at the evaporator. The dew point (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, This moisture is collected at the bottom of the evaporator in a condensate pan and removed by piping it to a central drain or onto the ground outside. A dehumidifier is an air-conditioner-like device that controls the humidity of a room or building. A dehumidifier is a Household appliance that reduces the level of Humidity in air usually for health reasons as humid air can cause Mold and They are often employed in basements which have a higher relative humidity because of their lower temperature (and propensity for damp floors and walls). Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water In food retailing establishments, large open chiller cabinets are highly effective at dehumidifying the internal air. Conversely, a humidifier increases the humidity of a building. A humidifier is a household Appliance that increases Humidity (moisture in a single room or in the entire home

Air-conditioned buildings often have sealed windows, because open windows would disrupt the attempts of the HVAC system to maintain constant indoor air conditions.

Energy efficiency

For the last 20-30 years, manufacturers of HVAC equipment have been making an effort to make the systems they manufacture more efficient. This was originally driven by rising energy costs, and has more recently been driven by increased awareness over environmental issues. There are several methods for making HVAC systems more efficient.

Heating energy

Water heating is more efficient for heating buildings and was the standard many years ago. Today forced air systems can double for air conditioning and are more popular. The most efficient central heating method is geothermal heating. Geothermal heating has been used since the time of the Roman Empire as a way of heating Buildings and Spas by utilizing sources of hot Water

Energy efficiency can be improved even more in central heating systems by introducing zoned heating. This allows a more granular application of heat, similar to non-central heating systems. Zones are controlled by multiple thermostats. A thermostat is a device for regulating the Temperature of a System so that the system's temperature is maintained near a desired setpoint In water heating systems the thermostats control zone valves, and in forced air systems they control zone dampers inside the vents which selectively block the flow of air. A zone valve is a specific type of Valve used to control the flow of Water or Steam in a hydronic heating or cooling system A damper is a valve or plate that stops or regulates the flow of air inside a duct, Chimney, VAV box, Air handler, or other air handling equipment

Ventilation Energy recovery

Energy recovery systems sometimes utilize heat recovery ventilation or energy recovery ventilation systems that employ heat exchangers or enthalpy wheels to recover sensible or latent heat from exhausted air. Energy recovery includes any technique or method of minimizing the input of Energy to an overall System by the exchange of energy from one sub-system of the overall Heat recovery ventilation (also known as a heat exchanger, air exchanger or air-to-air exchanger) is a ventilation system that employs a counter-flow Energy Recovery Ventilation is the process of exchanging the energy contained in normally exhausted building or space air and using it to treat the incoming outdoor ventilation A heat exchanger is a device built for efficient Heat transfer from one medium to another whether the media are separated by a solid wall so that they never mix or the media Sensible heat is Potential energy in the form of thermal energy or Heat. In Thermochemistry, latent heat is the amount of Energy in the form of Heat released or absorbed by a substance during a change of phase This is done by transfer of energy to the incoming outside fresh air.

Air conditioning energy

The performance of vapor compression refrigeration cycles is limited by thermodynamics. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " These AC and heat pump devices move heat rather than convert it from one form to another, so thermal efficiencies do not appropriately describe the performance of these devices. A heat pump is a machine or device that moves Heat from one location (the 'source' to another location (the 'sink' or 'heat sink' using work. In Thermodynamics, the thermal efficiency (\eta_{th} \ is a dimensionless performance measure of a thermal device such as an Internal combustion The Coefficient-of-Performance (COP) measures performance, but this dimensionless measure has not been adopted, but rather the Energy Efficiency Ratio (EER). To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER is used, and is the Seasonal Energy Efficiency Ratio (SEER). The SEER article describes it further, and presents some economic comparisons using this useful performance measure.

Major terms

Air Change per Hour (ACH)

The number of times per hour that the volume of a specific room or building is supplied or removed from that space by mechanical and natural ventilation.

Air handler, or air handling unit (AHU)

Central unit consisting of a blower, heating and cooling elements, filter racks or chamber, dampers, humidifier, and other central equipment in direct contact with the airflow. An air handler, or air handling unit (often abbreviated to AHU) is a device used to condition and circulate air as part of a heating ventilating and air-conditioning This does not include the ductwork through the building.

British thermal unit (BTU)

Any of several units of energy (heat) in the HVAC industry, each slightly more than 1 kJ. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity One BTU is the energy required to raise one pound of water one degree Fahrenheit, but the many different types of BTU are based on different interpretations of this “definition”. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 In the United States the power of HVAC systems (the rate of cooling and dehumidifying or heating) is sometimes expressed in BTU/hour instead of watts. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second.

Chiller

A device that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. A chiller is a machine that removes heat from a liquid via a vapor-compression or Absorption refrigeration cycle. This cooled liquid flows through pipes in a building and passes through coils in air handlers, fan-coil units, or other systems, cooling and usually dehumidifying the air in the building. Chillers are of two types; air-cooled or water-cooled. Air-cooled chillers are usually outside and consist of condenser coils cooled by fan-driven air. Water-cooled chillers are usually inside a building, and heat from these chillers is carried by recirculating water to outdoor cooling towers.

Coil

Equipment that performs heat transfer when mounted inside an Air Handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it. Air flowing across it is heated or cooled.

Condenser

A component in the basic refrigeration cycle that ejects or removes heat from the system. Thermodynamic heat pump and refrigeration cycles are the models for Heat pumps and Refrigerators. The condenser is the hot side of an air conditioner or heat pump. Condensers are heat exchangers, and can transfer heat to air or to an intermediate fluid (such as water or an aqueous solution of ethylene glycol) to carry heat to a distant sink, such as ground (earth sink), a body of water, or air (as with cooling towers).

Constant air volume (CAV)

A system designed to provide a constant air volume per unit time. Constant Air Volume ( CAV) is a type of heating ventilating and air-conditioning ( HVAC) system This term is applied to HVAC systems that have variable supply-air temperature but constant air flow rates. Most residential forced-air systems are small CAV systems with on/off control.

Controller

A device that controls the operation of part or all of a system. It may simply turn a device on and off, or it may more subtly modulate burners, compressors, pumps, valves, fans, dampers, and the like. Most controllers are automatic but have user input such as temperature set points, e. g. a thermostat. A thermostat is a device for regulating the Temperature of a System so that the system's temperature is maintained near a desired setpoint Controls may be analog, or digital, or pneumatic, or a combination of these. An analog or analogue signal is any continuous signal for which the time varying feature (variable of the signal is a representation of some other A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed

Damper

A plate or gate placed in a duct to control air flow by introducing a constriction in the duct. A damper is a valve or plate that stops or regulates the flow of air inside a duct, Chimney, VAV box, Air handler, or other air handling equipment

delta T

Delta T is a reference to a temperature difference. It is used to describe the difference in temperature of a heating or cooling fluid as it enters and as it leaves a heat transfer device. This term is used in the calculation of coil efficiency.

Evaporator

A component in the basic refrigeration cycle that absorbs or adds heat to the system. Within a Downstream processing system several stages are used to further isolate and purify the desired product Evaporators can be used to absorb heat from air (by reducing temperature and by removing water) or from a liquid. The evaporator is the cold side of an air conditioner or heat pump.

Fan coil unit (FCU)

A small terminal unit that is often composed of only a blower and a heating and/or cooling coil (heat exchanger), as is often used in hotels, condominiums, or apartments. A fan coil unit (FCU is a simple device consisting of a heating or cooling coil and fan. One type of fan coil unit is a unit ventilator.

Fresh air intake (FAI)

An opening through which outside air is drawn into the building. This may be to replace air in the building that has been exhausted by the ventilation system, or to provide fresh air for combustion of fuel.

Furnace

A component of an HVAC system that adds heat to air or an intermediate fluid by burning fuel (natural gas, oil, propane, butane, or other flammable substances) in a heat exchanger. A furnace is a device used for Heating The name derives from Latin fornax, Oven.

Grille

A facing across a duct opening, usually rectangular is shape, containing multiple parallel slots through which air may be delivered or withdrawn from a ventilated space.

Heat load, heat loss, or heat gain

Terms for the amount of heating (heat loss) or cooling (heat gain) needed to maintain desired temperatures and humidities in controlled air. Regardless of how well-insulated and sealed a building is, buildings gain heat from warm air or sunlight or lose heat to cold air and by radiation. Engineers use a heat load calculation to determine the HVAC needs of the space being cooled or heated.

Louvers

Blades, sometimes adjustable, placed in ducts or duct entries to control the volume of air flow. The term may also refer to blades in a rectangular frame placed in doors or walls to permit the movement of air.

Makeup air unit (MAU)

An air handler that conditions 100% outside air. MAUs are typically used in industrial or commercial settings, or in "once-through" (blower sections that only blow air one-way into the building), "low flow" (air handling systems that blow air at a low flow rate), or "primary-secondary" (air handling systems that have an air handler or rooftop unit connected to an add-on makeup unit or hood) commercial HVAC systems.

Packaged terminal air conditioner (PTAC)

An air conditioner and heater combined into a single, electrically-powered unit, typically installed through a wall and often found in hotels. A packaged terminal air conditioner (often abbreviated PTAC) is a type of self-contained Air conditioning and heating system commonly found in hotels and

Packaged unit or rooftop unit (RTU)

An air-handling unit, defined as either "recirculating" or "once-through" design, made specifically for outdoor installation. An air handler, or air handling unit (often abbreviated to AHU) is a device used to condition and circulate air as part of a heating ventilating and air-conditioning They most often include, internally, their own heating and cooling devices. RTUs are very common in some regions, particularly in single-story commercial buildings.

Thermal zone

A single or group of neighboring indoor spaces that the HVAC designer expects will have similar thermal loads. Building codes may require zoning to save energy in commercial buildings. Zones are defined in the building to reduce the number of HVAC subsystems, and thus initial cost. For example, for perimeter offices, rather than one zone for each office, all offices facing west can be combined into one zone. Small residences typically have only one conditioned thermal zone, plus unconditioned spaces such as unconditioned garages, attics, and crawlspaces, and unconditioned basements.

Variable air volume (VAV) system

An HVAC system that has a stable supply-air temperature, and varies the air flow rate to meet the temperature requirements. Variable air volume ( VAV) is a technique for controlling the capacity of a heating ventilating and/or air-conditioning ( HVAC) system Compared to CAV systems, these systems waste less energy through unnecessarily-high fan speeds. Most new commercial buildings have VAV systems.

Other HVAC equipment

HVAC industry and standards

In America

USA

Main article: American Society of Heating, Refrigerating and Air-Conditioning Engineers

(ASHRAE)

Main article: Uniform Mechanical Code

(Uniform Mechanical Code)

In Europe

In the United Kingdom

The Chartered Institute of Building Services Engineers is a body that covers the essential Service (systems architecture) that allow buildings to operate. An air conditioner is an Appliance, System, or mechanism designed to extract Heat from an area via a Refrigeration cycle An air filter is a device which removes solid Particulates such as Dust, Pollen, Mold, and bacteria from Air. A boiler is a closed vessel in which Water or other Fluid is heated Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. There are three types of chilled beam systems They are chilled ceilings passive chilled beams and active chilled beams A diffuser is the mechanical device that is designed to control the characteristics of a fluid at the entrance to a thermodynamic Open system. Ducts are used in heating ventilation and air conditioning ( HVAC) to deliver and remove air Economizers, or in British English economisers, are mechanical devices intended to reduce energy consumption or to perform another useful function like preheating a Fluid Evaporative coolers (also called swamp, desert, or air coolers) are devices that cool air through the simple Evaporation of water A mechanical fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat ventilation, exhaust A heat exchanger is a device built for efficient Heat transfer from one medium to another whether the media are separated by a solid wall so that they never mix or the media A humidifier is a household Appliance that increases Humidity (moisture in a single room or in the entire home A dehumidifier is a Household appliance that reduces the level of Humidity in air usually for health reasons as humid air can cause Mold and A HVAC control system is a computerized Control system for climate control in buildings For other uses see Pipe. Within Industry, piping is a system of pipes used to convey Fluids ( Liquids and For information on Wikipedia project-related discussions see WikipediaVillage pump. A fan coil unit (FCU is a simple device consisting of a heating or cooling coil and fan. For other uses see Valve (disambiguation. For the electronic component see Thermionic valve. A variable-frequency drive (VFD is a system for controlling the rotational speed of an Alternating current (AC Electric motor by controlling the frequency of the The American Society of Heating Refrigerating and Air Conditioning Engineers ( ASHRAE; pronounced 'ash'-'ray' is an international technical society for all individuals Designated as an American National Standard, the Uniform Mechanical Code (UMC is a model code developed by the International Association of Plumbing and Mechanical Officials The Chartered Institution of Building Services Engineers (CIBSE is a professional body based in London England that represents building services engineers and their various In the context of Enterprise architecture, Service-orientation, and Service-oriented architecture, the term service refers to a discretely defined set of It includes the electrotechnical, heating, ventilating, air conditioning, refrigeration and plumbing industries. Ventilation is the intentional movement of Air from outside a building to the inside The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort. Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable Plumbing, from the Latin plumbum for Lead, is the skilled trade of working with pipes, tubing and Plumbing fixtures for To train as a building services engineer, the academic requirement is GCSEs (A-C) / Standard Grades (1-3) in Maths and Science, which are important in measurements, planning and theory. A train is a connected series of vehicles that move along a track ( Permanent way) to transport freight or passengers from one place to another Employers will often want a degree in a branch of engineering, such as building environment engineering, electrical engineering or mechanical engineering. A degree is any of a wide range of status levels conferred by institutions of Higher education, such as universities, normally as the result of successfully completing Engineering is the Discipline and Profession of applying technical and scientific Knowledge and

Within the construction sector, it is the job of the building services engineer to design, install and maintain the essential services such as gas, electricity, water, heating and lighting, as well as many others. In the fields of Architecture and Civil engineering, construction is a process that consists of the Building or assembling of Infrastructure Design is used both as a Noun and a Verb. The term is often tied to the various Applied arts and Engineering (See design disciplines Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. These all help to make buildings comfortable and healthy places to live and work in. Building Services is part of a sector that has over 51,000 businesses and employs over 500,000 people. This sector has an annual turnover of £19. The Economy may be classified into subdivisions called sectors (also called Industries) in several ways 3 billion which represents 2%-3% of the GDP.

The most recognized standards for HVAC design is based on ASHRAE data. The American Society of Heating Refrigerating and Air Conditioning Engineers ( ASHRAE; pronounced 'ash'-'ray' is an international technical society for all individuals ASHRAE is the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The ASHRAE Handbook's most general volume, of four, is Fundamentals; it includes heating and cooling calculations. Each volume of the ASHRAE Handbook is updated every four years. The design professional must consult ASHRAE data for the standards of design and care as the typical building codes provides little to no information on HVAC design practices; such codes, such as the UMC and IMC, do include much details on installation requirements, however. Designated as an American National Standard, the Uniform Mechanical Code (UMC is a model code developed by the International Association of Plumbing and Mechanical Officials Other useful reference materials include items from SMACNA, ACCA, and technical trade journals. The Sheet Metal and Air Conditioning Contractors' National Association ( SMACNA; pronounced 'Smack'-'Nah' is an international association of HVAC contractors

See also

References

External links

• ASHRAE - The American Society of Heating, Refrigerating and Air-Conditioning Engineers

• Directory and Information resource for HVAC industry professionals
• Complete HVAC Visual Training
• The UK Selfbuild FAQ
• The effects of displacement ventilation
• Natural Ventilation - by Andy Walker of the National Renewable Energy Laboratory
• IEA Energy Conservation in Buildings and Community Systems Programme.
• BTU Calculator A worksheet by the Association of Home Appliance Manufacturers to help you estimate how much cooling capacity you need.
• HVAC Formulas - Common HVAC industry formula resource
• High Performance HVAC - Comprehensive articles about HVAC, HVAC applications, and saving energy with HVAC systems