Air Conditioning System

Window Air conditionersWindow Air conditioners

�� The control system (thermostat and selector The control system (thermostat and selector switch), switch),

�� electrical protection system (motor overload electrical protection system (motor overload

�� switches and winding protection thermostat switches and winding protection thermostat on the compress motor), on the compress motor),

�� air circulation system (fan motor, centrifugal air circulation system (fan motor, centrifugal evaporator blower and propeller fan for airevaporator blower and propeller fan for air--cooled condenser) and cooled condenser) and

�� ventilation (fresh air damper) and exhaust ventilation (fresh air damper) and exhaust systemsystem

InstallationInstallation

�� Ensure that there is liberal space on both the Ensure that there is liberal space on both the sides (minimum 30 cm on each side) for free sides (minimum 30 cm on each side) for free flow of air to the condenser fan, flow of air to the condenser fan,

�� So also the space behind the unit (condenser) So also the space behind the unit (condenser) should be clear (minimum 2 m) to allow free should be clear (minimum 2 m) to allow free flow of the hot condenser outlet air. flow of the hot condenser outlet air.

�� If there is any obstruction, the outlet air can If there is any obstruction, the outlet air can short cycle to the suction side of the condenser short cycle to the suction side of the condenser fan, leading to higher condensing temperature fan, leading to higher condensing temperature and consequent reduction in unit capacity.and consequent reduction in unit capacity.

InstallationInstallation

�� The best height of installation is about 75 to 120 The best height of installation is about 75 to 120 cm above the floor level for uniform circulation cm above the floor level for uniform circulation of supplyof supply--air across the living height of the air across the living height of the room. room.

�� It also ensures easy accessibility for service. Too It also ensures easy accessibility for service. Too high or too low an installation should be high or too low an installation should be avoided. avoided.

�� Do not install near a heating appliance, nor Do not install near a heating appliance, nor near a door or in a corner of the roomnear a door or in a corner of the room..

Split unitsSplit units

�� The indoor units are ceiling suspended, The indoor units are ceiling suspended, wall mounted or kept on floor as a console wall mounted or kept on floor as a console model and is generally known as the fan model and is generally known as the fan coil unitcoil unit


�� The distance between the indoor and The distance between the indoor and outdoor units has to be as small as outdoor units has to be as small as possible(maximum 10 m)possible(maximum 10 m)

�� As this distance increases the pressure As this distance increases the pressure drop in the suction and liquid lines also drop in the suction and liquid lines also increases, resulting in reduction of the unit increases, resulting in reduction of the unit capacitycapacity


�� Too high a vertical lift in the liquid line Too high a vertical lift in the liquid line (when outdoor unit is at a lower level) can (when outdoor unit is at a lower level) can cause flash gas in the liquid line. cause flash gas in the liquid line.

�� Also higher vertical lift of the suction line Also higher vertical lift of the suction line (when outdoor unit is at a higher level than (when outdoor unit is at a higher level than the indoor unit) can cause the problem of oil the indoor unit) can cause the problem of oil returnreturn

Package air conditionerPackage air conditioner�� These can be considered as the bigger versions of the These can be considered as the bigger versions of the

room air conditioners and are used for air room air conditioners and are used for air conditioning loads beyond the capacity range of the conditioning loads beyond the capacity range of the room air conditioners. room air conditioners.

�� They are available in nominal capacities of 3, 5, 7, 10, They are available in nominal capacities of 3, 5, 7, 10,

and 15 tonne. Like the room air conditioner, the and 15 tonne. Like the room air conditioner, the package unit also houses the air filtering, coolingpackage unit also houses the air filtering, cooling--dehumidifying and air handling components and is dehumidifying and air handling components and is factory assembled. factory assembled.

�� Components for heating and humidifying purposes Components for heating and humidifying purposes can also be included within the unit. can also be included within the unit.

�� The condenser can be of the waterThe condenser can be of the water--cooled or the aircooled or the air--cooled typecooled type..

Package air conditionerPackage air conditioner�� The waterThe water--cooled type can be completely cooled type can be completely factory assembled, charged (with refrigerant) factory assembled, charged (with refrigerant) and tested. and tested.

�� Thus the laying of refrigerant piping, pressure Thus the laying of refrigerant piping, pressure leak testing, evacuation. Charging. etc. need leak testing, evacuation. Charging. etc. need not have to be carried out in the field. not have to be carried out in the field.

�� This not only reduces the field labor, but also This not only reduces the field labor, but also ensures a cleaner system, being assembled in ensures a cleaner system, being assembled in the factory with strict quality control the factory with strict quality control proceduresprocedures

Package air conditionerPackage air conditioner�� The airThe air--cooled type obviously cannot be factory assembled cooled type obviously cannot be factory assembled and charged. Laying of the refrigerant piping between the and charged. Laying of the refrigerant piping between the indoor and outdoor units, pressure testing, evacuation, indoor and outdoor units, pressure testing, evacuation, charging, etc. have to be carried out in the field. charging, etc. have to be carried out in the field.

�� Because of the scarcity of water, airBecause of the scarcity of water, air--cooled units are favored, cooled units are favored, Though their capacity will be less than that of, the waterThough their capacity will be less than that of, the water--cooled condenser using the same compressor. cooled condenser using the same compressor.

�� For the evaporator side, centrifugal fans are provided, which For the evaporator side, centrifugal fans are provided, which can develop higher static pressure. So air distribution duct can develop higher static pressure. So air distribution duct and grills can be connected to the unit. and grills can be connected to the unit.

�� Air quantities generally ware 10 to 11.3 mAir quantities generally ware 10 to 11.3 m33 /min. (350 to 400 /min. (350 to 400 cfm) per toncfm) per ton

Central air conditioning plantsCentral air conditioning plants�� The central air conditioning system can be either of the direct The central air conditioning system can be either of the direct or the indirect type. or the indirect type.

�� In the direct system, the air from the space to be airIn the direct system, the air from the space to be air--conditioned is circulated over the cooling coil (of a conditioned is circulated over the cooling coil (of a refrigeration plant) in which the lowrefrigeration plant) in which the low--pressure refrigerant pressure refrigerant liquid is boiling. liquid is boiling.

�� The latent heat of vaporization for the liquid refrigerant is The latent heat of vaporization for the liquid refrigerant is taken from the air being circulated over the coil. So this is taken from the air being circulated over the coil. So this is known as the `Directknown as the `Direct--expansion (DX) system. expansion (DX) system.

�� In the indirect system, chilled water or brine from the In the indirect system, chilled water or brine from the refrigeration plant is circulated through the cooling coil refrigeration plant is circulated through the cooling coil located in the airlocated in the air--handling unit to cool and dehumidify the handling unit to cool and dehumidify the room air. Such a system is known as the central chilled water room air. Such a system is known as the central chilled water (or brine) system(or brine) system..

Chilled Water SystemChilled Water System

�� Though chilled water system requires more power per unit of Though chilled water system requires more power per unit of refrigeration (refrigeration (kw/tonnekw/tonne), the system offers plenty of ), the system offers plenty of flexibility in selection, lay out and operation. flexibility in selection, lay out and operation.

�� The chiller packages can be located in a central plant room, The chiller packages can be located in a central plant room, away from the airaway from the air--conditioned space. The airconditioned space. The air--handling units handling units too can be located at convenient locations for each zone/ area too can be located at convenient locations for each zone/ area and interconnected to the chiller packages with chilled water and interconnected to the chiller packages with chilled water lines. lines.

�� Multiple chiller packages interconnected on the water sides Multiple chiller packages interconnected on the water sides (chilled water as well as condenser water systems) can be (chilled water as well as condenser water systems) can be used for high loads, as high as say 1000 tonne. used for high loads, as high as say 1000 tonne.

�� For loads exceeding 200 tonne, waterFor loads exceeding 200 tonne, water--chilling packages with chilling packages with centrifugal compressors can be used, centrifugal compressors can be used,


�� Chilled water system is particularly suitable for air Chilled water system is particularly suitable for air conditioning of large hotels, multistoried office buildings, conditioning of large hotels, multistoried office buildings, industrial processingindustrial processing’’s, etc. s, etc.

As almost all the sides (generally three sides) of the rooms As almost all the sides (generally three sides) of the rooms are surrounded by airare surrounded by air--conditioned areas, the transmission conditioned areas, the transmission gain and so the sensible heat load of the room is generally gain and so the sensible heat load of the room is generally low.low.

Each room has to be provided with independent ON/OFF Each room has to be provided with independent ON/OFF and temperature control .Prevention of transmission of noise and temperature control .Prevention of transmission of noise (cross(cross--talk) from one room to the other.talk) from one room to the other.

Transmission of odors (such as smoking of cigars, Transmission of odors (such as smoking of cigars, cigarettes, food articles, human body odor etc.) from one cigarettes, food articles, human body odor etc.) from one room to another should be avoidedroom to another should be avoided


�� Air distribution through the ducts from a Air distribution through the ducts from a common aircommon air--handling unit for a number of handling unit for a number of rooms cannot be used. Here the fanrooms cannot be used. Here the fan--coil unit coil unit is the correct choice. is the correct choice.

�� FanFan--coil units are similar to the indoor unit in coil units are similar to the indoor unit in a split system room air conditioner except that a split system room air conditioner except that the chilled water coil replaces the DX coil. the chilled water coil replaces the DX coil.

�� Usually, a solenoid operated threeUsually, a solenoid operated three--way way diverting (or bydiverting (or by--pass) valve is provided on the pass) valve is provided on the inletinlet--chilled waterline to the unit.chilled waterline to the unit.


�� The valve is controlled by the room thermostat, When the The valve is controlled by the room thermostat, When the room temperature is above the set point, the solenoid coil of room temperature is above the set point, the solenoid coil of the threethe three--way valve is energized and the valve opens the port way valve is energized and the valve opens the port to supply chilled water to the coil. to supply chilled water to the coil.

�� When the thermostat goes off on temperature, the solenoid is When the thermostat goes off on temperature, the solenoid is de energized closing the supply port to the coil and opening de energized closing the supply port to the coil and opening the bythe by--pass port. pass port.

�� The byThe by--pass port is connected to the return chilled water line pass port is connected to the return chilled water line from the unit and thus the supplyfrom the unit and thus the supply--chilled water by passes the chilled water by passes the coil of the unit. coil of the unit.

�� A twoA two--way solenoid valve can also be used, but it has the way solenoid valve can also be used, but it has the disadvantage of creating `water hammer' (and associated disadvantage of creating `water hammer' (and associated banging noise) every time it closes. banging noise) every time it closes.

�� Further, when the twoFurther, when the two--way valve is closed, water flow to the way valve is closed, water flow to the

particular unit is stoppedparticular unit is stopped..

Refrigeration componentsRefrigeration components

�� Refrigeration unit / chillerRefrigeration unit / chiller

�� Compressor and motor condenserCompressor and motor condenser

�� Metering deviceMetering device

�� EvaporatorEvaporator

�� AccessoriesAccessories

�� Lubrication systemLubrication system

�� Safety and operational controlsSafety and operational controls

Air side components air handling unitsAir side components air handling units

�� Fan coil unitsFan coil units

�� Blower coil unitsBlower coil units

�� Fresh air Fresh air ahuahu

�� Ducting systemDucting system

�� Variable air volumesVariable air volumes

�� Grills and dampers controlsGrills and dampers controls

Water side componentsWater side components

�� Chilled water pumpsChilled water pumps

�� Chilled water piping systemChilled water piping system

�� Valves and strainersValves and strainers

�� Mixing valves Mixing valves

�� Double regulating valvesDouble regulating valves

�� Auto ventsAuto vents

�� Pressurization unitsPressurization units

Selecting a systemSelecting a system

Performance requirementsPerformance requirements

�� Capacity requirementsCapacity requirements�� Spatial requirementsSpatial requirements�� First costFirst cost�� Operating costOperating cost�� ReliabilityReliability�� FlexibilityFlexibility�� MaintainabilityMaintainability

Control optionsControl options

�� NoiseNoise

�� VentilationVentilation

�� FiltrationFiltration

�� Effect of failureEffect of failure

�� Space considerationsSpace considerations

�� Floor spaceFloor space

�� Plenum spacePlenum space

�� Furniture placementFurniture placement

�� MaintenanceMaintenance

�� accessibilityaccessibility

�� RoofsRoofs

�� First costFirst cost

�� System costSystem cost

�� Cost to add zonesCost to add zones

�� Ability to increase capacityAbility to increase capacity

�� Contribution to life safety Contribution to life safety needsneeds

�� Air quality controlAir quality control

�� Operating costsOperating costs

�� Energy costsEnergy costs

Control optionsControl options

�� ElectricityElectricity

�� Water costsWater costs�� Chemical costsChemical costs

�� Manpower costsManpower costs

�� Maintenance Maintenance costscosts

Labor costsLabor costs

Licensing for operatorsLicensing for operators

Material costsMaterial costs

EnergyEnergy--efficient operating efficient operating modesmodes

Economy cycle (free Economy cycle (free cooling)cooling)

Heat recoveryHeat recovery

The system selectionThe system selection�� 1.Does the system fit in the available space, or does it require1.Does the system fit in the available space, or does it require some some

architectural modification?architectural modification?

�� 2.Does the system use more floor space than others considered, o2.Does the system use more floor space than others considered, or does r does it require construction of additional space for mechanical roomsit require construction of additional space for mechanical rooms or or shafts?shafts?

�� 3.Will the system deliver the desired uniform temperature under 3.Will the system deliver the desired uniform temperature under varying weather and solar conditions? If compromises are made frvarying weather and solar conditions? If compromises are made from om the ideal control zoning, how much variation may be expected betthe ideal control zoning, how much variation may be expected between ween spacesspaces??

�� 4.How much will the system cost to own compared to others 4.How much will the system cost to own compared to others considered? What is the recovery time of the initial investment,considered? What is the recovery time of the initial investment, interest interest on investment system life, and the future cost of replacement on investment system life, and the future cost of replacement equipment?equipment?

�� 5.What are the operating costs for energy, maintenance, labor, a5.What are the operating costs for energy, maintenance, labor, and nd supplies of this system compared to others?supplies of this system compared to others?

The system selectionThe system selection�� What reliability can the owner expect compared to other What reliability can the owner expect compared to other systems? What component failures affect the entire building, systems? What component failures affect the entire building, and which affect only limited areas? How easily can the and which affect only limited areas? How easily can the system be serviced? How quickly can the system be restored system be serviced? How quickly can the system be restored to operation after various equipment failures?to operation after various equipment failures?

�� Is the system flexible enough to meet changes in the ownerIs the system flexible enough to meet changes in the owner’’s s needs? What is required to add a control zone? Can the needs? What is required to add a control zone? Can the system meet the increased capacity requirements of a space system meet the increased capacity requirements of a space when equipment is added? How will changes in the interior when equipment is added? How will changes in the interior layout and arrangement affect performance?layout and arrangement affect performance?

AllAll--Air SystemsAir Systems

�� An allAn all--air system provides complete sensible and latent air system provides complete sensible and latent cooling, preheating, and humidification capacity in the air cooling, preheating, and humidification capacity in the air supplied by the system. supplied by the system.

�� No additional cooling or humidification is required at the No additional cooling or humidification is required at the zone, except in the case of certain industrial systems. zone, except in the case of certain industrial systems.

�� Heating may be accomplished by the same air stream, either Heating may be accomplished by the same air stream, either in the central system or at a particular zone.in the central system or at a particular zone.

AllAll--air systems air systems -- advantagesadvantages

�� The location of the central mechanical room for major equipment The location of the central mechanical room for major equipment allows operation and maintenance to be performed in unoccupied allows operation and maintenance to be performed in unoccupied areas. In addition, it allows the maximum range of choices of areas. In addition, it allows the maximum range of choices of filtration equipment, vibration and noise control, and the selecfiltration equipment, vibration and noise control, and the selection tion of high quality and durable equipment.of high quality and durable equipment.

�� Keeping piping, electrical equipment, wiring, filters, and vibraKeeping piping, electrical equipment, wiring, filters, and vibration tion and noiseand noise--producing equipment away from the conditioned area producing equipment away from the conditioned area minimizes service needs and reduces potential harm to occupants,minimizes service needs and reduces potential harm to occupants,furnishings, and processesfurnishings, and processes

�� These systems offer the greatest potential for use of outside aiThese systems offer the greatest potential for use of outside air r (free cooling) instead of mechanical refrigeration for cooling.(free cooling) instead of mechanical refrigeration for cooling.

�� Seasonal changeover is simple and adapts readily to automatic Seasonal changeover is simple and adapts readily to automatic controlcontrol

�� A wide choice of zoning, flexibility, and humidity control underA wide choice of zoning, flexibility, and humidity control under all all operating conditions is possible, with the availability of operating conditions is possible, with the availability of simultaneous heating and cooling even during offsimultaneous heating and cooling even during off--season periods.season periods.

AllAll--air systems air systems -- advantagesadvantages

vi.vi. AirAir--toto--air and other heat recovery may be readily air and other heat recovery may be readily incorporated.incorporated.

vii.vii. They permit good design flexibility for optimum They permit good design flexibility for optimum air distribution, draft control, and adaptability to air distribution, draft control, and adaptability to varying local requirements.varying local requirements.

viii.viii.The systems are well suited to applications The systems are well suited to applications requiring unusual exhaust or makeup air quantities requiring unusual exhaust or makeup air quantities negative or positive pressurization, etc.)negative or positive pressurization, etc.)

ix.ix. All air systems adapt well to winter All air systems adapt well to winter humidification.humidification.

DisadvantagesDisadvantages

They require additional duct clearance, They require additional duct clearance, which reduces usable floor space and which reduces usable floor space and increases the height of the building.increases the height of the building.

AllAll--Water SystemsWater Systems

�� AllAll--water systems for heating and cooling use hot or water systems for heating and cooling use hot or chilled water for space conditioning, with the air in chilled water for space conditioning, with the air in the space heated or cooled by conduction, the space heated or cooled by conduction, convection, or radiation. The following are the convection, or radiation. The following are the principal types of allprincipal types of all--water systems:water systems:

i.i. Baseboard radiationBaseboard radiation

ii.ii. Freestanding radiators and convectorsFreestanding radiators and convectors

iii.iii. Wall, floor, or ceiling panelsWall, floor, or ceiling panels

iv.iv. Bare pipe (racked on wall)Bare pipe (racked on wall)

v.v. FanFan--coil unitscoil units

FanFan--coil unitscoil units

�� Four basic principles of air conditioning that also apply to Four basic principles of air conditioning that also apply to heating areheating are

i.i. Temperature controlTemperature control

ii.ii. Humidity controlHumidity control

iii.iii. Air movementAir movement

iv.iv. Air purity (filtration and outside air makeup)Air purity (filtration and outside air makeup)

�� Room fanRoom fan--coil units for the domestic market are generally coil units for the domestic market are generally available in nominal sizes ofavailable in nominal sizes of

�� 200, 300, 400, 600, 800, and 1200 cfm, often with multispeed, 200, 300, 400, 600, 800, and 1200 cfm, often with multispeed, highhigh--efficiency fan motors efficiency fan motors

Capacity ControlCapacity Control

�� FanFan--coil unit capacity can be controlled by coil water flow, air coil unit capacity can be controlled by coil water flow, air bypass, fan speed, or a combination of these. Water flow can bypass, fan speed, or a combination of these. Water flow can be thermostatically controlled by either return air or wall be thermostatically controlled by either return air or wall thermostatsthermostats

�� Fan speed control may be automatic or manual. Automatic Fan speed control may be automatic or manual. Automatic control is usually oncontrol is usually on--off with manual speed selection. Units off with manual speed selection. Units are available with variableare available with variable--speed motors for modulated speed speed motors for modulated speed control. Room thermostats are preferred where fan speed control. Room thermostats are preferred where fan speed control is used. Return air thermostats do not give a reliable control is used. Return air thermostats do not give a reliable index of room temperature when the fan is off.index of room temperature when the fan is off.

MaintenanceMaintenance

�� Room fanRoom fan--coil units are equipped with either cleanable or disposable coil units are equipped with either cleanable or disposable filters that should be cleaned or replaced when dirty. Good filtfilters that should be cleaned or replaced when dirty. Good filter er maintenance improves sanitation and provides full airflow, ensurmaintenance improves sanitation and provides full airflow, ensuring ing full capacity. full capacity.

�� The frequency of cleaning varies with the application. ApplicatiThe frequency of cleaning varies with the application. Applications in ons in apartments, hotels, and hospitals usually require more frequent apartments, hotels, and hospitals usually require more frequent filter filter service because of lint.service because of lint.

�� FanFan--coil unit motors require periodic lubrication. Motor failures arcoil unit motors require periodic lubrication. Motor failures are not e not common, but when they occur, it is possible to replace the entircommon, but when they occur, it is possible to replace the entire fan e fan quickly with minimal interruption in the conditioned space. The quickly with minimal interruption in the conditioned space. The defective motor can be repaired or replaced. defective motor can be repaired or replaced.

�� The condensate drain pan and drain system should be cleaned or The condensate drain pan and drain system should be cleaned or flushed periodically to prevent overflow and microbiological buiflushed periodically to prevent overflow and microbiological buildup. ldup. Drain pans should be trapped to prevent any gaseous backupDrain pans should be trapped to prevent any gaseous backup..

AdvantagesAdvantages

�� A major advantage of the allA major advantage of the all--water system is that the delivery system water system is that the delivery system (piping versus duct systems) requires less building space, a sma(piping versus duct systems) requires less building space, a smaller or ller or no central fan room, and little duct space. no central fan room, and little duct space.

�� The system has all the benefits of a central water chilling and The system has all the benefits of a central water chilling and heating heating plant, while retaining the ability to shut off local terminals iplant, while retaining the ability to shut off local terminals in unused n unused areas. It gives individual room control with little cross contamareas. It gives individual room control with little cross contamination of ination of recirculated air from one space to another.recirculated air from one space to another.

�� Extra capacity for quick pull down response may be provided. BecExtra capacity for quick pull down response may be provided. Because ause this system can heat with lowthis system can heat with low--temperature water, it is particularly temperature water, it is particularly suitable for solar or heat recovery refrigeration equipment. suitable for solar or heat recovery refrigeration equipment.

�� For existing building retrofit, it is often easier to install thFor existing building retrofit, it is often easier to install the piping and e piping and wiring for an allwiring for an all--water system than the large ductwork required for an water system than the large ductwork required for an allall--air system.air system.

DisadvantagesDisadvantages

�� AllAll--water systems require much more maintenance water systems require much more maintenance than central allthan central all--air systems, and this work must be air systems, and this work must be done in occupied areas. done in occupied areas.

�� Units that operate at low dew points require Units that operate at low dew points require condensate pans and a drain system that must be condensate pans and a drain system that must be cleaned and flushed periodically. Condensate cleaned and flushed periodically. Condensate disposal can be difficult and costly. It is also disposal can be difficult and costly. It is also difficult to clean the coil.difficult to clean the coil.

�� Filters are small, low in efficiency, and require Filters are small, low in efficiency, and require frequent changing to maintain air volume. In some frequent changing to maintain air volume. In some instances, drain systems can be eliminated if instances, drain systems can be eliminated if dehumidification is positively controlled by a dehumidification is positively controlled by a central ventilation air system.central ventilation air system.

AirAir--andand--Water SystemsWater Systems

�� AirAir--andand--water systems condition spaces by distributing air and water water systems condition spaces by distributing air and water sources to terminal units installed in habitable spaces throughosources to terminal units installed in habitable spaces throughout a ut a building. The air and water are cooled or heated in central mechbuilding. The air and water are cooled or heated in central mechanical anical equipment rooms. equipment rooms.

�� The air supplied is called primary air; the water supplied is caThe air supplied is called primary air; the water supplied is called lled secondary water. Sometimes a separate electric heating coil is isecondary water. Sometimes a separate electric heating coil is included ncluded in lieu of a hot water coil. This chapter is concerned primarilyin lieu of a hot water coil. This chapter is concerned primarily with airwith air--andand--water induction units, fanwater induction units, fan--coil units, and radiant panels as used in coil units, and radiant panels as used in airair--water systemswater systems

�� AirAir--andand--water systems apply primarily to exterior spaces of buildings water systems apply primarily to exterior spaces of buildings with high sensible loads and where close control of humidity is with high sensible loads and where close control of humidity is not not required. required.

�� They may, however, be applied to interior zones as well. These They may, however, be applied to interior zones as well. These systems work well in buildings such as office buildings, hospitasystems work well in buildings such as office buildings, hospitals, ls, hotels, schools, apartment buildings, and research laboratories.hotels, schools, apartment buildings, and research laboratories.

Air Conditioning System

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