Architecture - Centralized Air Conditioning System

Its the detailed process of the Centralized Air conditioning system. It is the apt notes required for architecture students. It has the components and sub topics with the detailed explanation of the mechanism of how it works

1. CENTRALISED AC SYSTEM GROUP 2

2. CONTENTS INTRODUCTION TO CENTRALISED SYSTEM COMPONENTS OF CENTRAL AC WORKING AND PRINCIPLE OF THE SYSTEM DUCTWORKS TYPES OF CENTRAL SYSTEM ADVANTAGES AND DISADVANTAGES CRITICAL ANALYSIS AND CASE STUDY

3. INTRODUCTION Air Conditioning- The process of removing heat and moisture content from an interior space. It can be used for both domestic and commercial spaces for cooling and dehumidifying these places. Central air conditions has a centralize duct system. The duct system (air distribution system) has an air handler, air supply system, air return duct and the grilles and register that circulates warm air from a furnace or cooled air from central air conditioning units to our room. It returns that air back to the system and starts again. It uses Ac refrigerant (we may know it as Freon) as a substance to absorb the heat from indoor evaporator coils and rejects that heat to outdoor condenser coils or vice verse.

4. The Refrigeration Cycle Using electricity as its power source, the refrigerant flows through a closed system of refrigeration lines between the indoor unit and the outside unit. Warm air from the inside of your house is pulled into ductwork by a motorized fan. The refrigerant is pumped from the exterior compressor coil to the interior evaporator coil, where it absorbs the heat from the air. This cooled air is then pushed through connecting ducts to vents throughout the home, lowering the interior temperature. The refrigeration cycle continues again, providing a consistent method to keep you cool .  

5. DUCT WORK AND PARTS Ductwork is simply an air delivery system. A delivery system for all forced air systems, furnace or air handler, heating or air conditioning, or both. Duct delivers fresh air and humidification into your home. Ductwork is the channel through which the air in your home is filtered and purified, or expelled to the outdoors and replaced with fresh new air. Each component of the ducted air delivery system, from the air handler to the registers, adds a certain amount of resistance to the airflow. This resistance is  friction loss

6.   Supply Plenum - usually on top of air handler for the initial distribution of conditioned air through connected ductwork. Return Air Drop - brings air from living space to air handler for conditioning and re-distribution. Flared Rectangular Take-off - connects to plenum to start ductwork. Reducer - usually 3 or 4 supply branches are connected to main trunk before a reducer changes duct size. Can be rectangular, square, or round. Top Take-off - connector for round branch lines to connect to main supply trunk. Can be square-to-round, oval-to-round, or round-to-round. Often are used as side take-offs also. Boots - delivers conditioned air into living space and houses the register. Stack head - a boot for a wall register. Wall stack - ductwork inside a wall to feed a stack head. Panning - flat metal nailed to joists for return air. Outside Air - Often a free flowing outide air is tied into the return ducting to keep some fresh air introduced into the residence. In extreme climates this ducting must be insulated, or condensation will occur.

7. SINGLE DUCT SYSTEM

8. DUAL DUCT SYSTEM TRANSITIONS-Rectangular Side Take-offs and Vertical Ells Every forced air duct system consists of many transitions, from rectangular to round, from trunk lines to branch lines, from the plenum to the main supply trunks, from the main return air trunk to the return air drop. Airflow is similar to water in that air will flow best where there is least restriction. The best ductwork transitions minimize restriction and help to balance airflow

9. COMPONENTS Parts of a Central AC System A typical central air conditioning system is a two-part or split system that includes:  The outdoor unit contains the condenser coil, compressor, electrical components and a fan. The evaporator coil, which is usually installed on top of the gas furnace inside the home. A series of pipes, or refrigeration lines, connecting the inside and outside equipment. Refrigerant, the substance in the refrigeration lines that circulates through the indoor and outdoor unit. Ducts that serve as air tunnels to the various spaces inside your home. A thermostat or control system to set your desired temperature.

10. COMPONENT OF CENTRAL AC SYSTEM  Air handling unit (AHU)  Supplying duct  Return duct  Diffusers/Registers  Compressor  Condenser  Expansion device  Evaporator  Thermostat 1)AIR HANDLING UNIT AHU IS used to Circulate ,Distribute and Regulate the conditioned air for HVAC buildings .

11. COMPONENTS OF AHU Supply duct Supply conditioned air for various heat loads Fan compartment Pressurize air to compensate pressure drop in duct Vibration ISOLATOR dampens the vibration in the unit caused by dynamic equipment Heating/cooling coil Controls the temperature and humidity to the required level Filter compartment filters the particulate matters to the required standards Mixing air duct Mixes return air with required amount of fresh air LOCATION at the top of the building and the door is always closed’ HOW TO CALCULATE SIZE OF AHU Select the velocity and volume (or next highest value) required from the table. Then, locate the unit size, external width and external height from the left hand column. Finally, add the base height to the external unit height and 50mm for a pitched roof if the unit will be sited in an external location.

12. 2) SUPPLYING DUCT It supplies the conditioned air from air handling unit (AHU) to the space or room. It is also called as main duct. From main duct a number of duct branches are provided for the each room. 3 ) RETURN DUCT This component is to regulate and extract air from a room and recycle it. Use of any ventilating, heating and air conditioning. The air will force air process which blows through the duct. Located either in hallway or in the ceiling at AHU Rooms .

13. 4) DIFFUSERS AND REGISTERS ALSO CALLED Return Air and Exhaust Air Inlets Grilles and registers are the two principal types of air inlets used to exhaust the air from a space or to return the air to the centrally located heating or cooling unit. The grilles are generally fixed-angle types because there is no need to direct air circulation when return air is involved. 5) COMPRESSOR The compressor is the heart of the cooling cycle. The cycle begins when the compressor draws in cool, low-pressure refrigerant gas from the indoors. The motor-driven compressor’s sole function is to "squeeze" the refrigerant, raising its temperature and pressure so that it exits the compressor as a hot, high-pressure gas . Heat Transfer Absorbs Heat

14. 6) CONDENSER The ac condenser and a car’s radiator often look quite similar in appearance. The compressor of the car generate compressed gas and sends it along to the top of the condenser, where the gas begin to cool. The gas continues to cool and condense as it makes its way through the serpentine-like coil arrangements, before exiting the bottom of the condenser as a high-pressure liquid. The condenser is usually located in front of your car’s radiator. 7) EXPANSION DEVICE Expansion device regulate the amount of liquid refrigerant flowing from the condenser to the evaporator based upon the evaporator pressure. A thermal expansion valve will include a temperature sensor and meters the amount of refrigerant flowing into the evaporator. 8) EVAPORATOR The ac evaporator serves in multiple capacities, but its function is to absorb heat which may have built up on a hot day inside the room. The evaporator contains cold Freon gas. The cold Freon gas passes through the evaporator and makes the evaporator very cold. The ac blower fan is located behind the evaporator and blows air across it and that cold air travels through the dash duct work and out the vents inside the room.

15. TWO TYPES OF THERMOSTAT System Operation With Basic Thermostat Deluxe Thermostat 1. SYSTEM OPERATION WITH BASIC THERMOSTAT System or Mode Control : Typically offers the following selections: Cool, Off, and Heat. Some thermostats also have Auto, which lets the system switch between heating and cooling as needed. Temperature Control : A button, lever, or set of buttons that allows you to select the temperature inside your home. Fan Control : Typically offers two options: Auto and On. ”Auto” provides slightly higher energy efficiency by circulating air only during cooling (or heating) operation. ”On” provides better air circulation, better dehumidification and better air cleaning by running the system’s blower continuously. 2. DELUXE THERMOSTATS Customized daily and/or weekly comfort schedules that you create to match your lifestyle Enhanced energy efficiency and comfort Enhanced comfort through humidity control Enhanced maintenance reminders  

16. WORKING AND PRINCIPLE An AC is like giant refrigerator for your house. It follows the principle refrigeration cycle. It has the same components as that for a refrigerator. AC gathers heat from one part of the building and transfers it to another. At the same time it cools another part and delivers chill to next place. The main component of air handler or furnace is placed somewhere it doesn’t collide with functions of the building where it provides chilled air . The placement of a thermostat is to either turn the cooling system on or off based on room temperature. The AC works on electricity. Hence during different periods of time the energy consumed may vary , hence the efficiency is a vital feature .

17. The first indication is provided by the thermostat - provides signal for ac to lower or raise temperature After the indication- ahu system is pressurized on drawing air from rooms through return air ducts. This pulled air is next sent to filters where dust, lint and other pollutant particles are removed and then sent to air supply ductwork from which blowers send the air back to rooms. Due to the refrigeration principles help in cooling the evaporator coil . Every air conditioner has three main parts: a condenser, an evaporator, and a compressor. The evaporator is mounted on or in the air-handling unit , which is often a forced-air furnace. Refrigerant circulates through copper tubing that runs between the evaporator and the condenser. This refrigerant receives and gives heat as temp is lowered and raised changing from liquid and gas and vice versa. Cold when it begins through inner coil. AHU pushes warm air through the coils and later into the outdoor coils. Either fans or metal “fins” helps in dissipating the heat accumulated. The refrigerants is then passed along the expansion device used to convert it into low pressure, low temperature liquid which returns to indoor coil.

18. The refrigeration system helps in removing heat from area of low pressure and low temperature (evaporator) to a higher temperature and high pressure area (condenser) Thermostat used to lower room temperature Air is drawn from the room –use of registers/diffusers Drawn air is next sent to filter then to blowers The air is circulated between cooper tubes connecting evaporator and condenser Heat is dissipated and then passed along expansion device and process continues

19. TYPES OF CENTRAL AIR CONDITIONERS There are two types of central air conditioners: a split system and a packaged unit .   In a split-system central air conditioner , an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or an air handler. The air conditioner's  evaporator coil  is installed in the cabinet or main supply duct of this furnace or heat pump. If your home already has a furnace but no air conditioner, a split system is the most economical central air conditioner to install.

20. In a packaged central air conditioner , the evaporator, condenser, and compressor are all located in one cabinet, which usually is placed on a roof or on a concrete slab next to the house's foundation. Air supply and return ducts come from indoors through the home's exterior wall or roof to connect with the packaged air conditioner, which is usually located outdoors. Packaged air conditioners often include electric heating coils or a natural gas furnace. This combination of air conditioner and central heater eliminates the need for a separate furnace indoors.

21. ADVANTAGES AND DISADVANTAGES ADVANTAGES- Central air conditioners offer one major benefit that individual window units cannot claim: Centralized units send cool air directly through air ducts or vents located in each room. Each room can be cooled instead of cooling just one room. Central air conditioners make less noise . The condenser, fan and compressor are located in an outdoor unit , instead of in a nearby window. Indoor noise is barely detectable. Since the working parts of a central air conditioner are located outside of the home, it is inconspicuous and does not affect the view from outside or within the home. Central air conditioners are easy to operate . Whether there is a single zone or multiple zones, the system is conveniently controlled by a simple console that can be programmed to run at certain times and temperatures. These systems can improve your indoor air quality .

22. DISADVANTAGES – The size for the AC unit is large. The cost of installing the system is high . High energy bills. Because central units rely on ducts, however, there is a high chance for energy waste and loss of efficiency as well as higher maintenance costs. Ductwork can be expensive and prone to leaking when damaged or due to deterioration from age. Unit requires annual maintenance . If you’re having a new system installed to replace or upgrade a current system, the ductwork may need to be updated or modified as well, to ensure it is compliant with the new system. Unlike a ductless system, you cannot individually adjust the temperature for each room .