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School of Planning and Architecture, New Delhi, B. Arch. III Year Section A

HVAC: Heating, Ventilation and Air Conditioning
Building Construction Report

Aishwarya Bharatkumar | Anuj Mittal | Bhavika Aggarwal | Vishal Jayan Ankit Sampatram | Navaneethakrishnan | Nikit Deshlahra | Vatsalya Sharma

CONTENTS
Contents ................................ ................................ ................................ ................................ ...................... 2 Introduction ................................ ................................ ................................ ................................ ................. 3 Air Conditioning for Cooling ................................ ................................ ................................ .......................... 3 Refrigeration Cycle ................................ ................................ ................................ ................................ ... 3 Working ................................ ................................ ................................ ................................ ................... 3 HVAC Systems ................................ ................................ ................................ ................................ .............. 4 Central Systems Versus Local Systems................................ ................................ ................................ ....... 4 Central System ................................ ................................ ................................ ................................ ......... 5 Local Systems ................................ ................................ ................................ ................................ ........... 6 Means Of Distribution ................................ ................................ ................................ ................................ .. 7 Air Supply Ducts ................................ ................................ ................................ ................................ ....... 7 Return Air Ducts and plenums................................ ................................ ................................ ................... 9 Terminal Devices ................................ ................................ ................................ ................................ .... 10 HVAC System Design and Installation ................................ ................................ ................................ .......... 11 design................................ ................................ ................................ ................................ ..................... 11 installation ................................ ................................ ................................ ................................ ............. 13 technical specifications (bluestar) ................................ ................................ ................................ ............... 19 Window ac ................................ ................................ ................................ ................................ ............. 19 Split ac................................ ................................ ................................ ................................ .................... 19 Tower ac................................ ................................ ................................ ................................ ................. 21 bibliography ................................ ................................ ................................ ................................ ............... 22

INTRODUCTION
The field of heating, ventilation, and air conditioning -HVAC- is the science and practice of controlling indoor climate to provide healthy and comfortable interior conditions. HVAC systems simultaneously control the temperature, humidity, purity, distribution and motion of the air in the interior spaces of the building. In the Indian context, HVAC systems are generally used to ventil ate and cool the building.

AIR CONDITIONING FOR COOLING
Air conditioning and refrigeration are provided through the removal of heat. Refrigeration may be defined as lowering the temperature of an enclosed space by removing heat from that space and transferring it elsewhere.

REFRIGERATION CYCLE
Vapour Compression refrigeration is one of the many refrigeration cycles available and is the most widely used method for air-conditioning. This refrigeration system uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere. The Vapour Compression refrigeration cycle depends on two physical properties of matter: 1. A large amount of heat is required to change a liquid into gas. This heat is again released when the gas condenses back into a liquid. 2. The boiling and condensation temperatures of any material are a function of pressure. When the pressure is reduced, the boiling point is also reduced.

WORKING
An air conditioner r emoves the warm air from inside and cycles back in as cooler air. This cycle continues until the thermostat reaches the desired temperature. A basic air conditioner unit consists of a condenser, an evaporator and a compressor.

The liquid refrigerant in the condenser coil (in red in the figure) enters the low pressure evaporator coil (in blue in the figure) through the valve A. The refrigerant boils/ evaporates due to the very low pressure, and thus consumes heat. The evaporator coil thus cools to allow the liquid refrigerant to change into a gas. To continue the cycle, the compressor B pumps the refrigerant gas into the condenser coil, and thus a high pressure gas collects at B. Since any gas under pressure heats up, the condenser coil gets hot. As the coil loses heat, the high pressure refrigerant gas is able to condense into the liquid refrigerant, which again enters the evaporator coil through the valve at A. Fans blow air over the coils to improve their ability to dissipate heat (to the outside air) and cold (to the room being cooled).

HVAC SYSTEMS
There are many HVAC systems to choose from depending upon floor space, visual obstructiveness, maintenance, cost, etc. The two major types of HVAC systems are 1. Central: In a central system, heat is supplied to a building or extracted from it by large equipment situated in one or several large mechanica l spaces. Air or water is heated or cooled in these spaces and distributed to the inhabited areas of the building by ductwork or piping to maintain comfortable temperatures. 2. Local: In a local system, independent, self-contained pieces of heating and cooli ng equipment are situated throughout the building, one or more in each room.

CENTRAL SYSTEMS VERSUS LOCAL SYSTEMS
Central systems are generally quieter and more energy efficient than local systems and offer better control of indoor air quality. Central equ ipment tends to last longer than local equipment and is more convenient to service. Local systems occupy less space in a building than central systems because they do not require central mechanical spaces, ductwork, or piping. They are often more economical to buy and install. They can be advantageous in buildings that have many small spaces requiring individual temperature control.

CENTRAL SYSTEM
Central air conditioning, commonly referred to as central air (U.S.) or air -con (UK), is an air conditioning system that uses ducts to distribute cooled and/or dehumidified air to more than one room, or uses pipes to distribute chilled water to heat exchangers in more than one room, and which is not plugged into a standard electrical outlet. With a typical split system, the condenser and compressor are located in an outdoor unit; the evaporator is mounted in the air handler unit. With a package system, all components are located in a single outdoor unit that may be located on the ground or roof. Central air conditioning performs like a regular air conditioner but has several added benefits: When the air handling unit turns on, room air is drawn in from various parts of the building through return-air ducts. This air is pulled through a filter where airborne particle s such as dust and lint are removed. Sophisticated filters may remove microscopic pollutants as well. The filtered air is routed to air supply ductwork that carries it back to rooms. Whenever the air conditioner is running, this cycle repeats continually. Because the condenser unit (with its fan and the compressor) is located outside the home, it offers a lower level of indoor noise than a free -standing air conditioning unit.

LOCAL SYSTEMS

WINDOW UNITS the common one room air conditioners, sit in a window or wall opening, with interior controls. Interior air is cooled as a fan blows it over the evaporator. On the exterior the air is heated as a second fan blows it over the condenser. In this process, heat is drawn from the room and discharged to the environment. A large house or building may have several such units, permitting each room be cooled separately. SPLIT UNITS PTAC systems are also known as wall split air conditioning systems or ductless systems. These PTAC systems which are frequently used in hotels have two separate units (terminal packages), the evaporative unit on the interior and the condensing unit on the exterior, with tubing passing through the wall and connecting them. This minimizes the interior system footprint and allows each room to be adjusted independently. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas or other heater, or by reversing the refrigerant flow to heat the i nterior and draw heat from the exterior air, converting the air conditioner into a heat pump. While room air conditioning provides maximum flexibility, when cooling many rooms it is generally more expensive than central air conditioning.

PACKAGED TERMINAL UNITS Like the previously described window air conditioning unit, packaged systems are preengineered , self contained units where most of the mechanical equipment is assembled

at the factory. Everything is in one unit except for the si te installed ducts. Consequently , they offer low installation, operating, and maintenance costs. Usually, small buildings are served by one package, while larger buildings get several. Roooftop versions are the most common, with each unit serving a separa te zone. Packaged units are sometimes used to on the ground for building with crawl spaces, above a suspended ceiling when there is enough space, or in an attic.

MEANS OF DISTRIBUTION
The distribution of heating and cooling energy involves the circulation of air (or water or both) to the inhabited spaces. The needed airflows include, for example, supply ai r, return air, exhaust air, and as part of the supply air, ventilation air.

AIR SUPPLY DUCTS
Air is usually supplied to rooms by means of ducts. However, building elements such as hollow-core concrete planks and hollow beams can also be used. A duct system is often called ductwork.

The purpose of the ductwork is to transport air from th e AHU to each outlet in the conditioned spaces at the specified velocity- and then back to the AHU. The air distribution velocity can either be high (above 2500 fpm or 12.7 m/s), medium (2200 - 2500 fpm or 11.2 to 12.7 m/s) or low (1000 - 2200 fpm or 5.1 to 11.2 m/s). SHAPE Although the size of ducts can be decreased by increasing the air velocity, it is more common to use large ducts and the resultant low velocity air flow because high velocity air flow requires more fan power to generate, and is much noi sier. A duct system is often described as a tree system in which the main trunk is the largest duct and the branches get progressively smaller. Ducts are either round, rectangular, or flat oval in cross section. Round ducts are preferable but require clearances that are not always available, and so are usually used only in the more expensive high velocity systems. Consequently, rectangular ducts are very popular for the typical low velocity systems. ASPECT RATIO The ratio of short to long sides in rectang ular ducts, the aspect ratio, should not exceed 1:5 because the resulting high air-flow friction requires the ducts to have excessively large areas and perimeters. MATERIALS Ducts are constructed of galvanized sheet metal, fibre glass, or (in corrosive environments) aluminum or stainless steel.

INSULATION Ductwork is usually insulated for the following purposes: 1. to reduce heat loss/ gain into ducted warm/ cool air 2. to prevent condensation on the exterior of cold air ducts when the surrounding air is warm and humid 3. to acoustically insulate air noises in the duct from the occupied space To prevent condensation, a vapor barrier must be on the outside of the insulation, while for noise control, the insulation must be exposed to the air stream. The metal duct wall serves as the vapor barrier, while fiberglass duct liner is frequently used to accomplish all acoustic/ thermal insulation. At least another 2 inches or 5 cm must be added to the dimensions of the ducts to account for the insulation. To prevent the ductwork itself from transmitting noise or vibrations from the AHU, a flexible fabric connection is used where the main ducts connect to the AHU. POSITIONING As much as possible, ducts should run parallel to deep structural elements and lighting fixtures to prevent wasted space when various building elements cross each other.

RETURN AIR DUCTS AND PLENUMS
Air return ducts are required and are about the same size, or slightly larger, than the main duct supply. (Even where air is supplied at high velocity, return air ductwork is always the larger, low velocity type.) Sometimes the return air system has a duct tree as extensive as that of the supply system. Often, however, the corridor or plenum above a hung ceiling is used instead of return air ducts. To maintain acoustical privacy, short return air ducts lined with sound absorbing insulation should connect rooms with the plenum. Corridors are sometimes used as return air plenums, but the need for undercut door thresholds or louvers in doors to permit a ir flow

when the doors are closed compromises acoustical privacy. When this cannot be avoided, special return air grilles with built in sound traps are also available for doors. Returns should be spaced so as to not interfere with air supply. Once air is returned to the

AHU it is either recirculated or exhausted.

TERMINAL DEVICES
The supply air enters a room through either a grille, register or a diffuser. Terminal devices interface the HVAC system with the building interiors for visual impact and thermal comfort. GRILLES AND REGISTER S A supply grille has adjustable vanes for controlling the direction of air entering a room. A register is a grille that also has a damper behind it so that the amount as well as the direction of air entering the room can be controlled. Grilles are side wall devices. Supply and return grilles or registers should be as far apart as possible in each space (ideally at opposite walls and opposite corners, and one near the ceiling and the other near the floor), and they should be l ocated where occupants or furnishings will not block them.

DIFFUSERS When air is supplied from the ceiling, it has to be mixed rapidly with the room air to prevent the discomfort of cold air striking the occupants; consequently, a diffuser is used. Diffusers are down-facing and must be coordinated with the lighting as well as uniformly spaced. They can be round, rectangular, or linear, and like registers, they have dampers for adjusting the volume of air being supplied. Supply air can also be diffuse d using large perforated ceiling panels.

HVAC SYSTEM DESIGN A ND INSTALLATION

The goal for a Heating, Ventilation and Air Conditioning (HVAC) system is to provide proper air flow, heating, and cooling to each room. This page sets out key criteria that describe a quality system, and key design and installation considerations that should be met to achieve this goal. The pages following contain more detailed information on design, fabrication, installation, and performance testing.
DESIGN

CRITERIA FOR A QUALITY HVAC SYSTEM

An HVAC system should: 1. Be properly sized to provide correct air flow, and meet room -by-room calculated heating and cooling loads. 2. Be installed so that the static air pressure drop across the handler is within manufacturer and design specifications to have the capacity to meet the calculated loads. 3. Have sealed supply ductwork that will provide proper air flow. 4. Be installed with a return system sized to provide correct return air flow. 5. Have sealed return ductwork that will provide proper a ir flow to the fan, and avoid air entering the HVAC system from polluted zones (e.g., fumes from autos and stored chemicals, and attic particulates). 6. Have balanced air flows between supply and return systems to maintain neutral pressure in the home.

7. Minimize duct air temperature gain or loss between the air handler and room registers, and between return registers and the air handler. 8. Be properly charged with refrigerant. 9. Have proper burner operation and proper draft.
PROCEDURES TO DESIGN AND INSTALL AN AIR DISTRIBUTION SYSTEM

The following steps should be followed in the design and installation of the HVAC system to ensure efficiency and comfort 1. Determine room-by-room loads and air-flows using ACCA Manual J calculation procedures (or substantially equivalent). 2. Layout duct system on floor plan, accounting for the direction of joists, roof hips, fire-walls, and other potential obstructions. Determine register locations and types, duct lengths, and connections required to produce layout given construction constraints. 3. Size duct system according to ACCA Manual D calculation procedures (or substantially equivalent). 4. Size HVAC equipment to sensible load using ACCA Manual S procedures (or substantially equivalent). 5. Install equipment and ducts according to design spe cifications, using installation requirements and procedures from the Uniform Mechanical Code, the Air Diffusion Council, SMACNA, California Residential Energy Efficiency Standards, and manufacturers' specifications, using these procedures, the duct system should be substantially air tight. 6. Charge the system appropriately, and verify charge with the evaporator superheat method or sub-cooling method (or substantially equivalent). 7. Check for proper furnace burner operation and fire -box drafting. 8. Test the system to ensure that it performs properly by determining that the system is properly sized, it does not leak substantially, and has either proper air handler fan flow, and proper plenum static pressures, or proper room and return air flows, and proper plenum static pressures.

INSTALLATION

An HVAC system is not as simple as it sounds. To properly install home HVAC ducts, you do need to perform some calculations to figure out what size duct you will need. If you don't already have this information handy, then you will need to hire a contract or to do it for you. The calculations involve measuring the size of the rooms, the A/C or heating unit, insulating properties of the home or its heat retention and many other factors.
INSTALLING OF METAL DUCTS

Metal HVAC ducts are the most common. They are rigid ducts that are installed in the ceiling or floor. The ducts are usually installed along the joists until the ducts need to make a turn to go into a room. Then a slot needs to be cut in the joists in order to route the ductwork through them. The d ucts themselves are installed with metal strips that wrap around the ducts and are screwed into the joists. Elbow joints are used to make the rigid ducts "turn" at a right angle or 45 -degree angle.
INSTALLING FLEXIBLE DUCTS

Flexible ducts are round tubing with a layer of insulation and a sleeve of high density plastic or a metalized material. They can bend around a corner so installing them can be a little easier than rigid ducts. These flexible ducts are typically installed in modern homes and sometimes used in attic A/C units. The ducts are routed from the A/C to rigid ducts in some cases. They do need to be routed in a specific way and can not bend past a certain point because it prohibits airflow.

INSTALLING A WINDOW AC

1 Measure the area you want to cool and calculate the size of the air conditioner you will need. (See below) 2 Determine where you want to install the air conditioner and measure the window opening. The air conditioner you buy needs to fit into the opening and all air conditioners aren't the same size.

3 Install the mounting brackets that came with the air conditioner unit (be sure to follow the manufacturer's directions). 4 Slide the air conditioner into the window opening and attach it to the mounting brackets (again as per manufacturer's instructions). 5 Lower the window down onto the top of the unit. 6 Pull out the extensions on each side of the air conditioner and attach them to the window frame. 7 Use a piece of foam (may be provided by the manufacturer), seal between the top of the air conditioner unit and the window. 8 Attach the drainage hose (if supplied) to the outside of the air conditioner. 9 Caulk around the outside of the unit to help keep the warm air outside. 10 Plug in your air conditioner, turn it on and enjoy that cool air.

INSTALLING A SPLIT AC

1) Indoor Unit: Here are the important suggestions when deciding the location of indoor unit inside the room: a) The indoor unit is located inside the room at the location from where the air can be distributed evenly throughout the room. b) As far as possible the indoor should be installed above the bed so that the maximum cooling effect can be obtained. It should be located directly above the bed. If one has to avoid the direct flow of chilled air on the body, one can always change the direction of the louvers. The indoor unit can also be installed on wall towards your feet though it can be installed on other side walls also. c) The wall mounted indoor unit should be located at the height of about 8 to 10 feet from the floor so that that most of the chilled air is used for cooling the room and not merely for cooling the hot roof. d) The indoor unit should be accessible easily so that one can conveniently clean the filter every fortnight and the whole unit and also that one can manually change the position of the louvers easily.

e) If the indoor unit is installed above certain window, make sure that it is in symmetry with the window, else the unit will look shabby. The indoor unit is meant to add to the aesthetics of the room and not destroy it. 2) Outdoor Unit: Here are some points to consider when deciding the location of the outdoor unit: a) The outdoor unit should be located in the open space preferably on the terrace so that the air can flow freely over the compressor and the condenser. If the terrace is not available it can be kept on the awning above the wall or it can be hanged on the external wall supported by the angles. b) The location of outdoor unit should be such that it is easily accessible for carrying out t he maintenance works of the compressor, condenser, and other devices. The installation and gas charging also should be convenient. c) There should not be any hindrances in front of the outdoor that would block the passage of fan air from passing to the ope n space. Any blockages will seriously affect the performance of the AC and can also lead to the burning of hermetically sealed compressor coil. d) The surface on which the outdoor unit is to be installed should be rigid enough to avoid its vibration. The vibration of the outdoor unit will raise excessive noise and also lead to the breaking of the copper tubing and leakage of the refrigerant. It is always advisable to keep the outdoor unit at the height above the indoor unit. If the outdoor unit is kept at l evel below the indoor, some of the compressor power is used in pumping the refrigerant against the gravity, thus reducing the overall performance of the compressor. Most of the outdoor units are quite silent so one does not have to worry about their noise. The internal parts of the outdoor unit are shielded against the rain and sun rays, so one can rest assured about their safety in different climatic conditions. The refrigerant at very low temperature flows inside the tubing between indoor and the outdoor unit, and there is always some loss of refrigerant effect to the atmosphere from these tubing, hence the distance between the indoor and the outdoor unit should be kept as minimum as possible to reduce the loss of the cooling effect. The maximum distance between the indoor and the outdoor units can be about 15 meters.

INSTALLING CENTRAL AC

Step 1: Components The first step to installing a central air conditioning is to understand how the system works.

1.Air conditioning systems consist of three main p arts: an outside unit, which typically includes thecondenser and compressor, an inside unit (air handler) where the evaporator is located, and ducts or pipes which distribute cold air or water to different rooms in a building. 2.Both the outside and inside unit will need to be connected to the main power supply of the home. 3.Sometimes the evaporator is located outside, eliminating the need for an inside unit. 4.If the air conditioning works by distributing cold air through several rooms, it will need ducts to do so. 5.If the air conditioning distributes cold water, which is turned into air in each separat e room, it will require pipes.

Step 2: Planning Before installing the air conditioning, you will need to do some planning. Follow the steps below to make sure you do everything in the right order and don't spend extra time and money fixing mistakes.

1.You will need to make sure that the main power supply supports the system you plan to install. Consult an electrician for this. This is very important, as it can be dangerous to connect a system not supported by the main power. 2.If you do not have ducts to transport the cold air, (or pipes to transport cold water), you will need to plan for and install these first. This will take much longer than the installa tion of the air conditioning system itself. 3.You should also contact a professional to help you determine how big of a unit you will need to cool down the home, or the rooms which you want the system to service.

4.The contractor should be certified or acc redited in Heating, Ventilation and Air Conditioning. 5.Handing refrigerants require an appropriate certification, so seek assistance for this part. If you are replacing an old air conditioning system, you should also ask a contractor to remove the old system.

Step 3: Installation Next, it's time to start the installation of the air conditioning. Follow all instructions and safety guidelines for the components you are installing carefully. Consult local planning and building codes for requirements on insta llation, including the placement of components.

1.Start by installing the air handler unit. It is usually installed in a basement or attic. Follow the instructions that came with the unit. 2.Make sure turn off the main power to the house or building next! Continuing with the installation while having the power on can be very dangerous! 3.Install the compressor. It should be placed on top of a base. The space immediately surrounding the compressor should be empty, so don't install it right next to a wall, p lants or other items. It should be placed on a stable and level surface. 4.Drill holes through the wall for the refrigeration and electricity tubes. Place filler between the wall and the tubes to prevent leakage. 5.Connect the compressor and air handler to the main power unit of the house. 6.Install the thermostat, if needed. Connect it to the air handler and main power supply. 7.Turn the power back on. 8.Check to make sure that the unit is working. Conclusion Installing a central air conditioning takes at least a few hours and will require some help from an electrician, unless you are one yourself. If you need pipes or ducts, it will take much longer. You might want to consult a contractor for additional help. If you are used to similar installations, you might be able to do the process yourself. Just make sure your main power supply supports the system before starting. The system described. A spilt system, the most common type of air central air system, is composed of three parts. The condenser and compres sor, which cool and move the

refrigerant, are installed outside, as they generate a lot of heat and noise. The evaporator and fan system, which cools and moves the air, is installed inside -usually in the attic or crawl space of your house. The ductwork carries the air from the evaporator to the rooms of your house. Got ducts? If your house has a forced -air heating system, your existing ductwork is probably sufficient. If not, ducts will need to be run from the evaporator/fan unit to the rooms of your house. For second floor rooms, ducts are run through the attic and dropped to through the ceiling into individual rooms. First floor rooms usually have the ducts run down through second floor closets. Flexible ductwork makes "closet running" simpler, but if you have closets that are heavily used or used by children, insist on sheet metal ductwork as flexible ducts are easily damaged.

INSTALLING HVAC DUCTS IN A BASE MENT

HVAC ducts transport warm and cool air from the HVAC unit to the supply air registers in the home. The most common place for HVAC ductwork to run is in the basement of the home, and the supply air registers are usually in the floor. If a home has a second story, there is usually a "duct chase" to allow the duct to rise from the basement to the sec ond floor. HVAC ducts are most commonly round and made out of galvanized metal. It can be a little challenging to install HVAC ducts in a basement; but if you are a home improvement guru, this is a task you can tackle. 1 Measure the distance between the two locations that you want to install HVAC duct and purchase the required amount of duct and elbows at your local home improvement store. 2 Install the HVAC duct by sliding the non -crimped end over the crimped end. The crimped end will slide into the non-crimped end approximately 1-1/2 inches. Secure the joints together with at least four sheet metal screws. 3 Cut down the duct as necessary with your snips if shorter pieces are required. You will have to crimp one end of the cut piece with your pipe cr imper to connect it with other duct. 4 Install elbows, as necessary, to make turns or offsets. They connect in the same fashion as the ductwork (by sliding over the crimped end and being secured with screws). 5 Support your ductwork at least every 5 feet with galvanized hanger strap. To support the duct, secure one end of the hanger strap to a ceiling joist, then loop it around the duct and secure the other end to a ceiling joist. The hanger will resemble the letter "U," and the duct will rest in the middle. 6 Seal all duct seams and joints with mastic duct sealer after the ductwork is installed. The mastic duct sealer comes in caulk tubes and is dispensed with a regular caulk gun. Allow

proper time for the mastic to cure before turning the HVAC system back on. Each brand of mastic duct sealer has a slightly different cure time so refer to the cure time that is listed on the label of the brand you purchased.

TECHNICAL SPECIFICAT IONS (BLUESTAR)

WINDOW AC

SPLIT AC

TOWER AC

BIBLIOGRAPHY
Websites: y y y y y y y y Books y heating, cooling, lighting sustainable design methods for architects http://en.wikipedia.org/wiki/HVAC http://en.wikipedia.org/wiki/Air_conditioning http://en.wikipedia.org/wiki/Duct_(HVAC) http://en.wikipedia.org/wiki/Refrigeration_cycle http://en.wikipedia.org/wiki/Vapor-compression_refrigeration http://home.howstuffworks.com/ac1.htm http://www.brighthub.com/engineering/mechanical/articles/45249.aspx

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