Technology of indoor and vehicular environmental comfort
Heating, ventilation, and air conditioning (HVAC)[1] is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers).
HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels, and senior living facilities; medium to large industrial and office buildings such as skyscrapers and hospitals; vehicles such as cars, trains, airplanes, ships and submarines; and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors.
Ventilating or ventilation (the "V" in HVAC) is the process of exchanging or replacing air in any space to provide high indoor air quality which involves temperature control, oxygen replenishment, and removal of moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases. Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, and prevents stagnation of the interior air. Methods for ventilating a building are divided into mechanical/forced and natural types.[2]
The three major functions of heating, ventilation, and air conditioning are interrelated, especially with the need to provide thermal comfort and acceptable indoor air quality within reasonable installation, operation, and maintenance costs. HVAC systems can be used in both domestic and commercial environments. HVAC systems can provide ventilation, and maintain pressure relationships between spaces. The means of air delivery and removal from spaces is known as room air distribution.[3]
In modern buildings, the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally estimate the capacity and type of system needed and then design the system, selecting the appropriate refrigerant and various components needed. For larger buildings, building service designers, mechanical engineers, or building services engineers analyze, design, and specify the HVAC systems. Specialty mechanical contractors and suppliers then fabricate, install and commission the systems. Building permits and code-compliance inspections of the installations are normally required for all sizes of buildings.
Although HVAC is executed in individual buildings or other enclosed spaces (like NORAD's underground headquarters), the equipment involved is in some cases an extension of a larger district heating (DH) or district cooling (DC) network, or a combined DHC network. In such cases, the operating and maintenance aspects are simplified and metering becomes necessary to bill for the energy that is consumed, and in some cases energy that is returned to the larger system. For example, at a given time one building may be utilizing chilled water for air conditioning and the warm water it returns may be used in another building for heating, or for the overall heating-portion of the DHC network (likely with energy added to boost the temperature).[4][5][6]
Basing HVAC on a larger network helps provide an economy of scale that is often not possible for individual buildings, for utilizing renewable energy sources such as solar heat,[7][8][9] winter's cold,[10][11] the cooling potential in some places of lakes or seawater for free cooling, and the enabling function of seasonal thermal energy storage. By utilizing natural sources that can be used for HVAC systems it can make a huge difference for the environment and help expand the knowledge of using different methods.
HVAC is based on inventions and discoveries made by Nikolay Lvov, Michael Faraday, Rolla C. Carpenter, Willis Carrier, Edwin Ruud, Reuben Trane, James Joule, William Rankine, Sadi Carnot, and many others.[12]
Multiple inventions within this time frame preceded the beginnings of the first comfort air conditioning system, which was designed in 1902 by Alfred Wolff (Cooper, 2003) for the New York Stock Exchange, while Willis Carrier equipped the Sacketts-Wilhems Printing Company with the process AC unit the same year. Coyne College was the first school to offer HVAC training in 1899.[13]
The invention of the components of HVAC systems went hand-in-hand with the industrial revolution, and new methods of modernization, higher efficiency, and system control are constantly being introduced by companies and inventors worldwide.
Heaters are appliances whose purpose is to generate heat (i.e. warmth) for the building. This can be done via central heating. Such a system contains a boiler, furnace, or heat pump to heat water, steam, or air in a central location such as a furnace room in a home, or a mechanical room in a large building. The heat can be transferred by convection, conduction, or radiation. Space heaters are used to heat single rooms and only consist of a single unit.
Heaters exist for various types of fuel, including solid fuels, liquids, and gases. Another type of heat source is electricity, normally heating ribbons composed of high resistance wire (see Nichrome). This principle is also used for baseboard heaters and portable heaters. Electrical heaters are often used as backup or supplemental heat for heat pump systems.
The heat pump gained popularity in the 1950s in Japan and the United States.[14] Heat pumps can extract heat from various sources, such as environmental air, exhaust air from a building, or from the ground. Heat pumps transfer heat from outside the structure into the air inside. Initially, heat pump HVAC systems were only used in moderate climates, but with improvements in low temperature operation and reduced loads due to more efficient homes, they are increasing in popularity in cooler climates, they can also operate in reverse by cooling an interior.
In the case of heated water or steam, piping is used to transport the heat to the rooms. Most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system (as opposed to older gravity-fed systems). The heat can be transferred to the surrounding air using radiators, hot water coils (hydro-air), or other heat exchangers. The radiators may be mounted on walls or installed within the floor to produce floor heat.
The use of water as the heat transfer medium is known as hydronics. The heated water can also supply an auxiliary heat exchanger to supply hot water for bathing and washing.
Warm air systems distribute the heated air through ductwork systems of supply and return air through metal or fiberglass ducts. Many systems use the same ducts to distribute air cooled by an evaporator coil for air conditioning. The air supply is normally filtered through air filters to remove dust and pollen particles.[15]
The use of furnaces, space heaters, and boilers as a method of indoor heating could result in incomplete combustion and the emission of carbon monoxide, nitrogen oxides, formaldehyde, volatile organic compounds, and other combustion byproducts. Incomplete combustion occurs when there is insufficient oxygen; the inputs are fuels containing various contaminants and the outputs are harmful byproducts, most dangerously carbon monoxide, which is a tasteless and odorless gas with serious adverse health effects.[16]
Without proper ventilation, carbon monoxide can be lethal at concentrations of 1000 ppm (0.1%). However, at several hundred ppm, carbon monoxide exposure induces headaches, fatigue, nausea, and vomiting. Carbon monoxide binds with hemoglobin in the blood, forming carboxyhemoglobin, reducing the blood's ability to transport oxygen. The primary health concerns associated with carbon monoxide exposure are its cardiovascular and neurobehavioral effects. Carbon monoxide can cause atherosclerosis (the hardening of arteries) and can also trigger heart attacks. Neurologically, carbon monoxide exposure reduces hand to eye coordination, vigilance, and continuous performance. It can also affect time discrimination.[17]
Ventilation is the process of changing or replacing air in any space to control the temperature or remove any combination of moisture, odors, smoke, heat, dust, airborne bacteria, or carbon dioxide, and to replenish oxygen. Ventilation often refers to the intentional delivery of the outside air to the building indoor space. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.[18]
Mechanical, or forced, ventilation is provided by an air handler (AHU) and used to control indoor air quality. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates more energy is required to remove excess moisture from ventilation air.
Kitchens and bathrooms typically have mechanical exhausts 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. Direct drive fans are available for many applications and can reduce maintenance needs.
In summer, ceiling fans and table/floor fans circulate air within a room for the purpose of reducing the perceived temperature by increasing evaporation of perspiration on the skin of the occupants. 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.
Natural ventilation is the ventilation of a building with outside air without using fans or other mechanical systems. It can be via operable windows, louvers, or trickle vents when spaces are small and the architecture permits. ASHRAE defined Natural ventilation as the flow of air through open windows, doors, grilles, and other planned building envelope penetrations, and as being driven by natural and/or artificially produced pressure differentials.[2]
In more complex schemes, warm air is allowed to rise and flow out high building openings to the outside (stack effect), causing cool outside air to be drawn into low building openings. Natural ventilation schemes can use very little energy, but care must be taken to ensure comfort. In warm or humid climates, maintaining thermal comfort solely via natural ventilation might not be possible. Air conditioning systems are used, either as backups or supplements. Air-side economizers also use outside air to condition spaces, but do so using fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate.
An important component of natural ventilation is air change rate or air changes per hour: the hourly rate of ventilation divided by the volume of the space. For example, six air changes per hour means an amount of new air, equal to the volume of the space, is added every ten minutes. For human comfort, a minimum of four air changes per hour is typical, though warehouses might have only two. Too high of an air change rate may be uncomfortable, akin to a wind tunnel which has thousands of changes per hour. The highest air change rates are for crowded spaces, bars, night clubs, commercial kitchens at around 30 to 50 air changes per hour.[19]
Room pressure can be either positive or negative with respect to outside the room. Positive pressure occurs when there is more air being supplied than exhausted, and is common to reduce the infiltration of outside contaminants.[20]
Natural ventilation [21] is a key factor in reducing the spread of airborne illnesses such as tuberculosis, the common cold, influenza, meningitis or COVID-19. Opening doors and windows are good ways to maximize natural ventilation, which would make the risk of airborne contagion much lower than with costly and maintenance-requiring mechanical systems. Old-fashioned clinical areas with high ceilings and large windows provide the greatest protection. Natural ventilation costs little and is maintenance free, and is particularly suited to limited-resource settings and tropical climates, where the burden of TB and institutional TB transmission is highest. In settings where respiratory isolation is difficult and climate permits, windows and doors should be opened to reduce the risk of airborne contagion. Natural ventilation requires little maintenance and is inexpensive.[22]
An air conditioning system, or a standalone air conditioner, provides cooling and/or humidity control for all or part of a building. Air conditioned buildings often have sealed windows, because open windows would work against the system intended to maintain constant indoor air conditions. Outside, fresh air is generally drawn into the system by a vent into a mix air chamber for mixing with the space return air. Then the mixture air enters an indoor or outdoor heat exchanger section where the air is to be cooled down, then be guided to the space creating positive air pressure. The percentage of return air made up of fresh air can usually be manipulated by adjusting the opening of this vent. Typical fresh air intake is about 10% of the total supply air.[citation needed]
Air conditioning and refrigeration are provided through the removal of heat. Heat can be removed through radiation, convection, or conduction. The heat transfer medium is a refrigeration system, such as water, air, ice, and chemicals are referred to as refrigerants. A refrigerant is employed either in a heat pump system in which a compressor is used to drive thermodynamic refrigeration cycle, or in a free cooling system that uses pumps to circulate a cool refrigerant (typically water or a glycol mix).
It is imperative that the air conditioning horsepower is sufficient for the area being cooled. Underpowered air conditioning systems will lead to power wastage and inefficient usage. Adequate horsepower is required for any air conditioner installed.
The refrigeration cycle uses four essential elements to cool, which are compressor, condenser, metering device, and evaporator.
In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a facility to be heated and cooled by a single piece of equipment by the same means, and with the same hardware.
Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so that the cold of winter can be used for summer air conditioning. Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat-exchanger-equipped boreholes. Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added-in because the storage acts as a heat sink when the system is in cooling (as opposed to charging) mode, causing the temperature to gradually increase during the cooling season.
Some systems include an "economizer mode", which is sometimes called a "free-cooling mode". When economizing, the control system will open (fully or partially) the outside air damper and close (fully or partially) the return air damper. This will cause fresh, outside air to be supplied to the system. When the outside air is cooler than the demanded cool air, this will allow the demand to be met without using the mechanical supply of cooling (typically chilled water or a direct expansion "DX" unit), thus saving energy. The control system can compare the temperature of the outside air vs. return air, or it can compare the enthalpy of the air, as is frequently done in climates where humidity is more of an issue. In both cases, the outside air must be less energetic than the return air for the system to enter the economizer mode.
Central, "all-air" air-conditioning systems (or package systems) with a combined outdoor condenser/evaporator unit are often installed in North American 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.[23] (Minisplit ductless systems are used in these situations.) Outside of North America, packaged systems are only used in limited applications involving large indoor space such as stadiums, theatres or exhibition halls.
An alternative to packaged systems is the use of separate indoor and outdoor coils in split systems. Split systems are preferred and widely used worldwide except in North America. In North America, split systems are most often seen in residential applications, but they are gaining popularity in small commercial buildings. Split systems are used where ductwork is not feasible or where the space conditioning efficiency is of prime concern.[24] The benefits of ductless air conditioning systems include easy installation, no ductwork, greater zonal control, flexibility of control, and quiet operation.[25] In space conditioning, the duct losses can account for 30% of energy consumption.[26] The use of minisplits can result in energy savings in space conditioning as there are no losses associated with ducting.
With the split system, the evaporator coil is connected to a remote condenser unit using refrigerant piping between an indoor and outdoor unit instead of ducting air directly from the outdoor unit. Indoor units with directional vents mount onto walls, suspended from ceilings, or fit into the ceiling. Other indoor units mount inside the ceiling cavity so that short lengths of duct handle air from the indoor unit to vents or diffusers around the rooms.
Split systems are more efficient and the footprint is typically smaller than the package systems. On the other hand, package systems tend to have a slightly lower indoor noise level compared to split systems since the fan motor is located outside.
Dehumidification (air drying) in an air conditioning system is provided by the evaporator. Since the evaporator operates at a temperature below the dew point, moisture in the air condenses on the evaporator coil tubes. This moisture is collected at the bottom of the evaporator in a pan and removed by piping 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. It is often employed in basements that have a higher relative humidity because of their lower temperature (and propensity for damp floors and walls). 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.
The HVAC components that dehumidify the ventilation air deserve careful attention because outdoor air constitutes most of the annual humidity load for nearly all buildings.[27]
All modern air conditioning systems, even small window package units, are equipped with internal air filters. These are generally of a lightweight gauze-like material, and must be replaced or washed as conditions warrant. For example, a building in a high dust environment, or a home with furry pets, will need to have the filters changed more often than buildings without these dirt loads. Failure to replace these filters as needed will contribute to a lower heat exchange rate, resulting in wasted energy, shortened equipment life, and higher energy bills; low air flow can result in iced-over evaporator coils, which can completely stop airflow. Additionally, very dirty or plugged filters can cause overheating during a heating cycle, which can result in damage to the system or even fire.
Because an air conditioner moves heat between the indoor coil and the outdoor coil, both must be kept clean. This means that, in addition to replacing the air filter at the evaporator coil, it is also necessary to regularly clean the condenser coil. Failure to keep the condenser clean will eventually result in harm to the compressor because the condenser coil is responsible for discharging both the indoor heat (as picked up by the evaporator) and the heat generated by the electric motor driving the compressor.
HVAC is significantly responsible for promoting energy efficiency of buildings as the building sector consumes the largest percentage of global energy.[28] Since the 1980s, 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 of environmental issues. Additionally, improvements to the HVAC system efficiency can also help increase occupant health and productivity.[29] In the US, the EPA has imposed tighter restrictions over the years. There are several methods for making HVAC systems more efficient.
In the past, water heating was more efficient for heating buildings and was the standard in the United States. Today, forced air systems can double for air conditioning and are more popular.
Some benefits of forced air systems, which are now widely used in churches, schools, and high-end residences, are
A drawback is the installation cost, which can be slightly higher than traditional HVAC systems.
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. 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. In this case, the control system is very critical to maintaining a proper temperature.
Forecasting is another method of controlling building heating by calculating the demand for heating energy that should be supplied to the building in each time unit.
Ground source, or geothermal, heat pumps are similar to ordinary heat pumps, but instead of transferring heat to or from outside air, they rely on the stable, even temperature of the earth to provide heating and air conditioning. Many regions experience seasonal temperature extremes, which would require large-capacity heating and cooling equipment to heat or cool buildings. For example, a conventional heat pump system used to heat a building in Montana's 57C (70F) low temperature or cool a building in the highest temperature ever recorded in the US57C (134F) in Death Valley, California, in 1913 would require a large amount of energy due to the extreme difference between inside and outside air temperatures. A metre below the earth's surface, however, the ground remains at a relatively constant temperature. Utilizing this large source of relatively moderate temperature earth, a heating or cooling system's capacity can often be significantly reduced. Although ground temperatures vary according to latitude, at 1.8 metres (6ft) underground, temperatures generally only range from 7 to 24C (45 to 75F).
Photovoltaic solar panels offer a new way to potentially decrease the operating cost of air conditioning. Traditional air conditioners run using alternating current, and hence, any direct-current solar power needs to be inverted to be compatible with these units. New variable-speed DC-motor units allow solar power to more easily run them since this conversion is unnecessary, and since the motors are tolerant of voltage fluctuations associated with variance in supplied solar power (e.g., due to cloud cover).
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. This is done by transfer of energy from the stale air inside the home to the incoming fresh air from outside.
The performance of vapor compression refrigeration cycles is limited by thermodynamics.[30] These air conditioning 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. The Coefficient of performance (COP) measures performance, but this dimensionless measure has not been adopted. Instead, the Energy Efficiency Ratio (EER) has traditionally been used to characterize the performance of many HVAC systems. EER is the Energy Efficiency Ratio based on a 35C (95F) outdoor temperature. To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER, the Seasonal Energy Efficiency Ratio (SEER), or in Europe the ESEER, is used. SEER ratings are based on seasonal temperature averages instead of a constant 35C (95F) outdoor temperature. The current industry minimum SEER rating is 14 SEER.[31] Engineers have pointed out some areas where efficiency of the existing hardware could be improved. For example, the fan blades used to move the air are usually stamped from sheet metal, an economical method of manufacture, but as a result they are not aerodynamically efficient. A well-designed blade could reduce the electrical power required to move the air by a third.[32]
Demand controlled kitchen ventilation (DCKV) is a building controls approach to controlling the volume of kitchen exhaust and supply air in response to the actual cooking loads in a commercial kitchen. Traditional commercial kitchen ventilation systems operate at 100% fan speed independent of the volume of cooking activity and DCKV technology changes that to provide significant fan energy and conditioned air savings. By deploying smart sensing technology, both the exhaust and supply fans can be controlled to capitalize on the affinity laws for motor energy savings, reduce makeup air heating and cooling energy, increasing safety, and reducing ambient kitchen noise levels.[33]
Air cleaning and filtration removes particles, contaminants, vapors and gases from the air. The filtered and cleaned air then is used in heating, ventilation, and air conditioning. Air cleaning and filtration should be taken in account when protecting our building environments.[34]
Clean air delivery rate (CADR) is the amount of clean air an air cleaner provides to a room or space. When determining CADR, the amount of airflow in a space is taken into account. For example, an air cleaner with a flow rate of 30 cubic metres (1,000cuft) per minute and an efficiency of 50% has a CADR of 15 cubic metres (500cuft) per minute. Along with CADR, filtration performance is very important when it comes to the air in our indoor environment. This depends on the size of the particle or fiber, the filter packing density and depth, and the airflow rate.[34]
The HVAC industry is a worldwide enterprise, with roles including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry was historically regulated by the manufacturers of HVAC equipment, but regulating and standards organizations such as HARDI (Heating, Air-conditioning and Refrigeration Distributors International), ASHRAE, SMACNA, ACCA (Air Conditioning Contractors of America), Uniform Mechanical Code, International Mechanical Code, and AMCA have been established to support the industry and encourage high standards and achievement. (UL as an omnibus agency is not specific to the HVAC industry.)
The starting point in carrying out an estimate both for cooling and heating depends on the exterior climate and interior specified conditions. However, before taking up the heat load calculation, it is necessary to find fresh air requirements for each area in detail, as pressurization is an important consideration.
ISO 16813:2006 is one of the ISO building environment standards.[35] It establishes the general principles of building environment design. It takes into account the need to provide a healthy indoor environment for the occupants as well as the need to protect the environment for future generations and promote collaboration among the various parties involved in building environmental design for sustainability. ISO16813 is applicable to new construction and the retrofit of existing buildings.[36]
The building environmental design standard aims to:[36]
In the United States, HVAC engineers generally are members of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), EPA certified (for installation and service of HVAC devices), or locally engineer certified such as a Special to Chief Boilers License issued by the state or, in some jurisdictions, the city. ASHRAE is an international technical society for all individuals and organizations interested in HVAC. The Society, organized into regions, chapters, and student branches, allows the exchange of HVAC knowledge and experiences for the benefit of the field's practitioners and the public. ASHRAE provides many opportunities to participate in the development of new knowledge via, for example, research and its many technical committees. These committees typically meet twice per year at the ASHRAE Annual and Winter Meetings. A popular product show, the AHR Expo, has been held in conjunction with each winter ASHRAE meeting. The Society has approximately 50,000 members and has headquarters in Atlanta, Georgia.
The most recognized standards for HVAC design are based on ASHRAE data. The four volumes of most popular ASHRAE Handbooks are Fundamentals, Refrigeration, HVAC Applications, and HVAC Systems and Equipment. The current versions of the four handbooks are shown below:[37]
Each volume of the ASHRAE Handbook is updated every four years. The Fundamentals Handbook includes heating and cooling calculations. The design professional must consult ASHRAE data for the standards of design and care as the typical building codes provide little to no information on HVAC design practices; codes such as the UMC and IMC do include much detail on installation requirements, however. Other useful reference materials include items from SMACNA, ACGIH, and technical trade journals.
American design standards are legislated in the Uniform Mechanical Code or International Mechanical Code. In certain states, counties, or cities, either of these codes may be adopted and amended via various legislative processes. These codes are updated and published by the International Association of Plumbing and Mechanical Officials (IAPMO) or the International Code Council (ICC) respectively, on a 3-year code development cycle. Typically, local building permit departments are charged with enforcement of these standards on private and certain public properties.
An HVAC technician is a tradesman who specializes in heating, ventilation, air conditioning, and refrigeration. HVAC technicians in the US can receive training through formal training institutions, where most earn associate degrees. Training for HVAC technicians includes classroom lectures and hands-on tasks, and can be followed by an apprenticeship wherein the recent graduate works alongside a professional HVAC technician for a temporary period.[citation needed] HVAC techs who have been trained can also be certified in areas such as air conditioning, heat pumps, gas heating, and commercial refrigeration.
The Chartered Institution of Building Services Engineers is a body that covers the essential Service (systems architecture) that allow buildings to operate. It includes the electrotechnical, heating, ventilating, air conditioning, refrigeration and plumbing industries. To train as a building services engineer, the academic requirements are GCSEs (A-C) / Standard Grades (1-3) in Maths and Science, which are important in measurements, planning and theory. Employers will often want a degree in a branch of engineering, such as building environment engineering, electrical engineering or mechanical engineering. To become a full member of CIBSE, and so also to be registered by the Engineering Council UK as a chartered engineer, engineers must also attain an Honours Degree and a master's degree in a relevant engineering subject.[citation needed] CIBSE publishes several guides to HVAC design relevant to the UK market, and also the Republic of Ireland, Australia, New Zealand and Hong Kong. These guides include various recommended design criteria and standards, some of which are cited within the UK building regulations, and therefore form a legislative requirement for major building services works. The main guides are:
Within the construction sector, it is the job of the building services engineer to design and oversee the installation and maintenance of the essential services such as gas, electricity, water, heating and lighting, as well as many others. 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 represents 2%-3% of the GDP.
The Air Conditioning and Mechanical Contractors Association of Australia (AMCA), Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH), Australian Refrigeration Mechanical Association and CIBSE are responsible.
Asian architectural temperature-control have different priorities than European methods. For example, Asian heating traditionally focuses on maintaining temperatures of objects such as the floor or furnishings such as Kotatsu tables and directly warming people, as opposed to the Western focus, in modern periods, on designing air systems.
The Philippine Society of Ventilating, Air Conditioning and Refrigerating Engineers (PSVARE) along with Philippine Society of Mechanical Engineers (PSME) govern on the codes and standards for HVAC / MVAC (MVAC means "mechanical ventilation and air conditioning") in the Philippines.
The Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) was established to promote the HVAC industry in India. ISHRAE is an associate of ASHRAE. ISHRAE was founded at New Delhi[38] in 1981 and a chapter was started in Bangalore in 1989. Between 1989 & 1993, ISHRAE chapters were formed in all major cities in India.[citation needed]
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Heating, ventilation, and air conditioning - Wikipedia
Trailer Wiring Diagram and Installation Help - Towing 101
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Any vehicle towing a trailer requires trailer connector wiring to safely connect the taillights, turn signals, brake lights and other necessary electrical systems.
If your vehicle is not equipped with a working trailer wiring harness, there are a number of different solutions to provide the perfect fit for your specific vehicle. Complete with acolor coded trailer wiring diagram of each plug type, this guide walks through each available solution, including custom wiring, splice-in wiring and replacement wiring.
If you're looking to replace the wiring on your trailer, check out ourtrailer rewiring guide.
A. Custom wiring
Vehicle-specific plug-and-play harness that requires no splicing and provides a standard trailer connector
B. Splice-in wiring
Taillight converter that splices into your existing vehicle wiring and provides a standard trailer connector
Custom wiring is the ideal solution for installing trailer light wiring on your vehicle. A custom wiring harness or 'T-connector' is a vehicle-specific harness that plugs in without any spicing required and provides a standard connector output, such as a 4-way flat.
All CURT custom wiring comes with the exact components needed for a complete installation on the vehicle, including vehicle-specific plugs and an electrical converter, if needed.
Another type of custom wiring is original-equipment (OE) wiring or USCAR wiring. Select vehicles come with a standardized USCAR socket that provides a connection point for a CURT OE wiring harness.
Like a T-connector, anoriginal equipment wiring harnessplugs into the USCAR socket without any cutting, splicing or soldering required, and it provides a standard trailer wiring output, such as a 4-way flat or 7-way RV blade.
Learn more about USCAR wiring
If custom wiring is not available for your particular make and model, a taillight converter may be required to equip your vehicle with the proper trailer light wiring connection.
A taillight converter or electrical converter splices into your vehicle and provides a standard trailer plug wiring connector, typically a 4-way flat. The converter converts the vehicle's complex wiring system to be compatible with your trailer's simple wiring system. To learn more about vehicle wiring systems, check out ourvehicle wiring systems guide.
If the trailer plug wiring on your vehicle or trailer is damaged or not working correctly, you can replace the connector with a CURT splice-in plug or socket.
Plugs (trailer side) and sockets (vehicle side) are available in all standard formats and can be spliced into your existing tow wiring. Find the trailer light wiring diagram below that corresponds to your existing configuration.
If you are rewiring your trailer completely, check out ourtrailer rewiring guide.
Following the standard method for wiring a trailer connector is vital to the safety of your vehicle while towing. Connecting the wrong color wires will result in mismatched taillight functions and confusion on the road.
Use this 4-pin wiring diagram to properly wire your 4-wire trailer plug.
GreenRight turn / brakesYellowLeft turn / brakesBrownTaillightsWhiteGround
5-pin trailer wiring is very similar to 4-pin wiring, but it adds in a blue wire for the reverse or backup lights.
Not all trailers have reverse lights, so consider your own trailer as you wire in a 5-way plug.
BlueReverse lightsGreenRight turn / brakesYellowLeft turn / brakesBrownTaillightsWhiteGround
6-pin trailer wiring introduces two new functions, a wire for connecting trailer brakes and a wire for +12-volt auxiliary power.
6-way wiring is most common on gooseneck trailers and allows for use with a brake controller.
BrownTaillightsBlueElectric brakesGreenRight turn / brakesYellowLeft turn / brakesWhiteGroundBlack+12 volt
The 7-way round trailer plug is to be distinguished from 7-way RV blade plugs. The wiring connections and placement are different.
Be sure to review your own trailer connector before wiring.
WhiteGround BrownTaillights GreenRight turn / brakes RedAuxiliary power YellowLeft turn / brakes BlackReverse lights BlueElectric brakes
The SAE configuration of a 7-way RV blade plug should not be confused with the traditional configuration. Different wire colors are used for different functions.
Review your own trailer before wiring.
BrownTaillightsYellowLeft turn / brakesWhiteGroundBlueElectric brakesGreenRight turn / brakesOrange+12 voltGreyReverse lights
7-pin trailer wiring is one of the most popular wiring configruations, particularly the traditional configuration versus the SAE J2863.
Use this 7-pin trailer wiring diagram to properly wire your 7-pin trailer plug.
GreenTaillights RedLeft turn / brakes WhiteGround BlueElectric brakes BrownRight turn / brakes Black+12 volt YellowReverse lights
Note: Not all trailers are equipped with reverse lights (yellow wire). The position of this wire may vary for your own specific setup.
Note: The ground wire color on all trailer plug types is always white. Other colors vary in function, depending on the configuration.
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The traditional 7-way RV blade format is typically used on 5th wheel trailers, travel trailers and campers. The trailer wiring colors for this configuration are different than those on the SAE configuration.
The SAE J2863 7-way RV blade format is typically used on gooseneck trailers, utility trailers, cargo trailers and equipment trailers.
Trailers are equipped with different plug types based on their electrical components. The chart below provides examples of common trailers and the types of plugs they typically use.
Utility trailer
4-way flat
6-way round
7-way RV blade
Boat trailer without surge brakes
4-way flat
7-way RV blade (rarely used)
Boat trailer with surge brakes
5-way flat
6-way round
7-way RV blade
Pop up camper
6-way square
6-way round
Travel trailer
7-way RV blade
6-way round
7-way round
5th wheel trailer
7-way RV blade
6-way round
Gooseneck trailer
6-way round
7-way RV blade
Learn more about different trailer types here. Refer to the wiring diagrams above for functions of trailer wiring colors.
Discover more great tips and how-tos on theLippert blog-- your destination for all things RVing, towing, boating and beyond!
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Trailer Wiring Diagram and Installation Help - Towing 101
Single Phase 120V/230V Distribution and Panel Board Wiring in Home
Single Phase wiring installation is the most common wiring in residential buildings. In Single Phase supply (230V in UK, EU and 120V & 240V in the US & Canada), there are two (one is Line (aka Phase, Hot or Live) and the other one is Neutral) incoming cables from the utility poles to the kWh energy meter and then directly connected to the main distribution board (Consumer unit).
In this step by step tutorial, we will show how to wire a single Phase Consumer Unit Installation in home from Utility Pole to a Single-Phase Energy Meter & Single-Phase Distribution board and then How to connect Single Phase Loads in single Phase Wiring Distribution System in home electric supply system.
Before go in details, you will have to know what is a Single Phase and Three Phase Supply, their applications as well as the role of RCD, MCB, MCCB, CB, DB, MDB, Final and Sub Circuits, Fuses, Switches etc.which is already discussed in our previous electrical wiring installation tutorials.
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The following different levels of voltages are available for domestics (as residential) and commercial (as industrial) application in the US, Canada (following NEC and CNC) and UK, EU and other countries which follows the IEC e.g. India, Pakistan, UAE, KSA, Philippine, South Africa, Nigeria, Indonesia etc. The following fig at the end of this section will help you easily understand the difference between single phase and three phase voltage levels in the NEC and IEC.
In the USA, for single phase 120V and split phase or 240V, the secondary winging of the distribution transformer mounted on the utility pole is center-tapped i.e. two hot wires (Hot 1 and Hot2) and the center wire as Neutral. This way, the voltage level between Hot and Neutral is 120V single phase and voltage between two hots (Hot 1 & Hot 2) is 240V single phase.
Single Phase Voltage Levels in the USA
Three Phase Voltage Levels in the USA
i.e.
And
Related Wiring Tutorials:
In a Three Phase Wiring Distribution System (Star Connection i.e. 3 Phase, 4 Wire System); The power and distribution transformers may be wired in Star (Y) or Delta configuration). For example, the basic configuration for single phase and three phase system in the UK is 230V/400V where the primary of the distribution transformer mounted on the utility pole is connected in Delta Connection while the secondary is connected in Star or Y Connection.
This way, the Voltage between any phase and neutral is 230V single phase, while the voltage level between three lines are 400V three phase.
Single Phase Voltage Levels in the UK & EU
Three Phase Voltage in the UK & EU
I.e.
And
120V, 208V, 240V, 277V & 480V, Single Phase and Three Phase Supply Voltage Systems NEC US
120V, 208V & 240V High Leg Delta Configurations
230V & 400V Single Phase & Three Phase Power Supply Systems IEC UK & EU
Related Wiring Tutorials:
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To Wire and install a single phase consumer unit for electric supply distribution in multi sections of a house, follow the steps given below:
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If you have to install a single phase mains distribution system in different sections around the home (large area), follow the following important things before doing so.
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Single Phase 120V & 240V Distribution and Panel Wiring in home.
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Single Phase 120V & 208V Distribution and Panel Wiring in home.
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Single Phase 120V & 208V & 240V (High Leg Delta) Distribution and Panel Wiring in home.
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Single Phase 277V & 480V Distribution and Panel Wiring in home.
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Good to know: it is against the code to use two separate single pole circuit breakers for 208V or 240V circuits. If you still want to connect two SP breakers as double pole for 240V circuit, the switches of both breakers should be bonded and connected together i.e. both SP breakers should be switched ON & OFF with the same common switch. In addition, use the proper rated breaker, wire size, outlets, and switches etc. (check the bottom note (instruction & precaution) for calculators and tutorials about wire size, sizing outlets, switches and socket etc.
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Single Phase 230V Distribution and Consumer Unit Wiring in Multi-sections of home.
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Single Phase, 230V Consumer Unit & Distribution Board Wiring with RCD
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Single Phase, 230V Split Load Consumer Unit & Distribution Board Wiring
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Single Phase, 230V Dual Split Load Consumer Unit & Distribution Board Wiring
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Good to Know: According to IET (Institution of Engineering and Technology) wiring regulations: 17th Edition (BS 7671:2008 1: 2011), an RCD protection must be provided in the consumer unit except smoke and burglar alarms system.
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There is no much difference in IEC and NEC wiring for single phase MCBs and associated wiring i.e. a single phase expect for 240V. In other words, 120V single phase load can be connected directly to the single pole MCB via three wires e.g. Black as Hot, White as Neutral and green with yellow stripe or bare conductor as protective ground.
In 240V single phase wiring, the load can be connected to the double pole MCB via three or four wires (as Neutral is always needed in that case and depends on the system design) i.e. Black as Hot 1, Red as Hot 2, White as Neutral (optional) and green/yellow stripe or bare conductor for ground wire.
Below are some typical single phase wiring diagrams used for power distribution in the home (United States of America and Canada).
Wiring Installation of Single Phase 120V Circuits & Breakers in Main Service Panel
Wiring Installation of Single Phase 120V & 240V Circuits & Breakers in Main Service Panel
Wiring Installation of Single Phase 120V & 208V Circuits & Breakers in Main Service Panel
Wiring Installation of Single Phase 120V, 208V & 240V (High Leg Delta) Circuits & Breakers in Main Service Panel
Wiring Installation of Single Phase 277V & 480V Circuits & Breakers in Main Service Panel
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For Single Phase Loads (230V or 120V) Washing Machines, TV, Power socket, Lighting Points, Fans etc., can be directly connected to the Phase and Neutral wire through proper wiring and controlling as shown below. Note that Earth or ground wire must be connected to each of the electrical appliances and equipment connected to both single phase and three phase supply systems to avoid electric shock and hazard.
Wiring single phase 230V load and MCB in the Distribution board and consumer unit with RCD.
Wiring single phase 230V Split Load load and MCB in the Distribution board and consumer.
Wiring single phase 230V Dual Split Load load and MCB in the Distribution board and consumer.
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Below is given layout wiring diagram of single phase consumer unit installation in a residential area.
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We have used Red for Phase, Live or Hot, Black for Neutral and Green for Earth/Ground Wire in the typical single phase wiring diagram. You may use the specific region or general practiced codes in the local area i.e. IEC International Electrotechnical Commission (UK, EU etc.) or NEC (National Electrical Code [US & Canada] see the detailed post about NEC & IEC wiring Color Codes where;
NEC USA:
Single Phase 120V AC:
Single Phase 240V AC:
Three Phase 208V & 240V AC (High Leg Delta):
Three Phase 277V & 480V AC:
IEC & UK:
Single Phase 230V AC:
Three Phase 400V:
For reference, here is the OLD UK Wiring Color Codes (Prior 2004) which still applicable in other countries i.e. India, Pakistan, UAE, KSA and other Arab Countries.
400V Three Phase
230V Single Phase
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You may also check the related Electrical Wiring Installation Tutorials.
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Single Phase Electrical Wiring Installation in Home NEC & IEC
