AIRCONDITIONING BASICS

AIR-CONDITIONING CAPACITY• TR or ton of refrigeration - unit of measure of all air

conditioners. • Indicates a certain quantity of heat.• British thermal unit (BTU) is the quantity of heat needed

to raise the temperature of 1 pound of water by 1 degree F

• Calorie is the metric unit of heat quantity. It is heat needed to raise temperature of 1 gm of water by 1 deg C. 1000 Cal = 1 kilo calorie (K Cal)

• 1TR = 12000 BTU = 3000 K Cal

AIR CONDITIONING IN TODAY'S CONTEXT:

• In hot climate the air has to be cooled, • in cold climate the air has to be heated, • in dusty space the air has to be cleaned and • In all the above cases the air has to be properly

distributed. • Here air conditioning is required mainly for

human comfort. • But some times for other purposes like

manufacturing goods, medicine, textiles etc the temperature and humidity control may vary. For this purpose also air conditioning is required.

AIR CONDITIONING PROCESS

• Controlling the quality of indoor air for the benefit of Human comfort, human health and performance of equipment /process.

• Human comfort is related to the control of temperature, humidity and air movement.

• A process called REFRIGERATION controls the temperature and humidity.

• The human health is related to the control of dust, pollutants and other contaminants. This is achieved by filtration or by dilution of air.

DEFINITIONS• process of treating air and simultaneously

controlling temp, humidity, impurities and distribution for comfort and health of human being and/ or for the industrial process permitting the best product yield during manufacture and storage.

• Process, which heats, cools, cleans and circulates air and controls its moisture content, simultaneously and on a year round basis.

• Science, which deals with supplying and maintaining desirable internal atmospheric conditions irrespective of external conditions. Temperature control, humidity control, air movement & circulation, air filtering/ cleaning/ purification.

TEMPERATURE CONTROL

• Temperature most suited to majority of people• It varies in summer (20 to 23 deg C) and winter

(18 to 22 deg C) due to body temperature• Office, club, lounge etc – 24.5deg C• Residence, Hotel rooms, Guest house etc –

24deg C• Shops, super markets, Cinema halls, Public

places – 23.5deg C• Major operation theatre – 21deg C• Computer rooms, Laboratories etc – 22deg C

HUMIDITY CONTROL

• Amount of moisture present in air

• Varies from place to place & time to time

• Coastal areas are more humid

DEHUMIDIFICATION

• Removal of excess moisture from the air

HUMIDIFICATION

• Adding moisture to any volume

RELATIVE HUMIDITY

• Ratio of amount of water vapour present in air to maximum amount of vapour the air can hold in a given temperature

• If the temperature increases the capacity to hold moisture also increases

At 70°F, 8 grains = 100%. At 80°F, 11 grains = 100%. • To increase RH, increase actual moisture content or

decrease the temperature of the air. • To decrease RH, decrease the moisture content or

increase the temperature of the air. • 100% indicates the saturation level

• Human comfort – 55 + 5%• Pharmaceutical – 45 + 5%• Computer lab etc – 50 + 5%• Spinning & weaving – 65 + 5%• Low humidity - the air has very less moisture

content. The air has tendency to absorb moisture from the surrounding.

• High humidity – uncomfortable, reduces evaporation process through skin and in turn cooling of body. Our body maintain comfort by perspiration as in coastal weather

AIR MOVEMENTKeeps the body comfortable during hot weather.

Increase in air movement results in, • Increase of evaporation process as the moisture

of skin evaporates faster • Increase of convection process as the warm air

next to the body is carried up faster. • Increase of radiation process due to removal of

heat from the surrounding surfaces• Decrease in air movement decreases

evaporation, convection and radiation which, decreases heat removal process from our body, keeps the body comfortable in cold weather

• Air movement is created by - fans or blowers, through ducts for even distribution

VENTILATION IN AC AREAS

• It is supply of fresh air, its circulation and distribution

• Same air cannot be re-circulated again and again. After some time some fresh air may be added for human comfort. This is done through a cowl (small opening) in AHU room.

• In rooms provided with window AC system always allow some fresh air when ac is not being used.

DUST CONTROL

DUST CONTROL IN AC AREAS

• Dust enters ac areas through openings like door etc

• Through occupants

• Use different types of filters

PURITY & FILTERS:

• Air to be free from dust, dirt and other impurities• Clean air for breathing and human health• In food product manufacture place dirt, germs

create harmful effects• Clean air needed in manufacturing processes• Clogging of dirt etc., may create serious hazards to

machinery parts

To maintain purity Air filters are used. • Filters are normally located in R.A. path• Various filters effectively reduce the above hazards

FILTERS

All air filters can be divided into five basic types.

• Dry filters• Viscous impingement filters• Electronics filters• Chemical filters• Carbon filters• Submission particulate “absolute” filters

1 Dry filtersThey separate dust, pollen and bacteria by using fabrics of

woven cotton, wool, felt, cellulose or fiber glass. The filter is supported in wire or angle frame located in

return air path. Fiber glass media is less expensive and very widely used.Confined to smaller systems. Sizes - 450 x 450, 500 x 500,

600 x 600, etcAirflow required is up to 5-metre cube per second. Permanent dry type• Efficiency 95%. Materials – fabrics processed from

plastics or brush type. • Serviced by washing or by compressed air or vacuum

cleaning.

Dry filtersDry replaceable media type• Efficiency 95%. Fabric media over metal frame • Serviced by replacing the media. • Used as main filter or as pre filter to high efficiency filters. Throwaway type – • Efficiency up to 95%. Used in smaller plants• Panels with filter media of fabrics, plastics, glass or metal

fibre over wood or metal frame. Standard filter -• a) Metallic filter – ½”, 1”, 13/4” thick.• b) Polypropylene coir filter – ¼” thick.• These are used in simple applications of comfort A/c.• It can be used in central, packaged and window units.• Dust filteration is up to 25 to 30 microns.

2 VISCOUS IMPINGEMENT FILTERS• screen or mesh in a metal frame. • Glass fibre or other fiber filter medium covered with

viscous adhesive or oil film to retain dust particles.• Metal media impingement filters are washed with hot

water / steam / solvent to remove dust particles. Later it is cleaned with oil solution.

• Expensive Impingement filter - available in automatic roll models

Viscous impingement filter – • Efficiency 80 – 90% Used for industrial or engine air

taker.• Serviced by washing and reoiling. Automatic air filters -• Efficiency up to 90%. Used for larger systems. • Operation normally time switch controlled. • Deposited dust can be removed manually.

Self Cleaning Viscous Type Air Filter (Oil Wetted) For removal of coarse and abrasive dust usually used as first stage filter in industrial application. To remove fibrous dust from the main air stream. very tough and rigid Area like Cotton/ Textile/ Jute/ Mills, Steel & Cement Plants, Fertilizer Units, DG set house etc. Self cleaning in nature, easy/ low maintenance Available on various designs in multiple sizes to suit clients exact requirements .

3 ELECTRONIC FILTERS• High voltage used to attract dust particles over

electrically charged plates installed in the return air path. • Impingement filters as pre-filter to remove coarse dust

particles & to create constant pressure across the plates.

• Removes smoke & fine particles, initial cost is high.

Electrostatic cleaners Achieve optimum filtration level down to 0.1 micron. To be backed by microwave filters or pre filtersBooster fan is not necessary for this

ELECTROSTATIC FILTER1. Dirt Laden Air2. Pre-Filter Screen3. Electronic Filter Cell4. Activated Carbon Filter5. Circulating Fan

6. Clean Fresh Air

NASAL AIR FILTER

This Indian patented product is not yet produced in India.It is available in other countries for the use of people. In India it has a large market as the dust pollution is at it's high in the Indian cities. People and Children are exposed to the pollution, dust and stink which causes severe health problems.This simple, soft, disposable, cost effective ( Rs 2/-per one day use) filter have a market of 10 million in Indian cities daily.Gives you a pleasant fragrance always when you walk through dusty smelly road sides, and while talking to others you are protected form airborne communicable diseases.I am ready to sell the patent right to the reputed company who wish to produce and market the filter in India.

4 CHEMICAL FILTERS

• consists of a belt with nozzles on top.

• Nozzles spray solution of glycerine, germicide and odour absorbing chemicals.

• Absorbs dust, dirt, bacteria,odour etc.

• Solution collected in a basin at the bottom & When saturated with contaminants, cleaned by chemicals and recirculated.

• Very expensive and used in hospitals etc.

5 CARBON FILTERS• To remove objectionable odor from the air. • Useful when outside air polluted • Useful when same air is re-circulated continuously

Carbon pack filter – • To remove odours, fumes, vapours, gasses, etc. • Carbon is activated and this filter quickly clogged

with atmospheric dust. • As per the manufacturers recommendation

throwaway type OR reusable type may be adopted

CARBON FILTER

ACTIVATED CARBON FILTER

Activated Carbon - Odour Absorbing Filter The simple human activated carbon filter naturally absorbs odors.

After extended use, the filter's odor absorbing ability can be recharged by placing it in direct sunlight. HOW TO USE simply peel off the double-sided adhesive tape on the back of the filter and attach to a clean surface area where there are odors, such as the underside of your trash can's lid or inside a cabinet door

6 ABSOLUTE FILTERS• Pleated continuous sheet of filter of glass-

asbestos medium with ply wood, metal frame. The pleats are separated by corrugated paper or aluminum foil inserts.

• Used to filter airborne contaminants to protect life, to recover valuable products or in clean rooms

• Hospitals - to remove bacteria, Atomic reactors - to remove radioactive dust, Food and drug plants - to provide sterile air

• Dry filter as pre-filter to remove coarse dust particle for better efficiency.

HIGH EFFICIENCY PARTICULATE AIR (HEPA) OR ABSOLUTE FILTERS

• For filtration below 5 microns. Filter particles down to 0.3 microns. Used in central A/c, package unit, etc.

• Booster fans are needed for this. Microwave and metallic filters as pre-filters

Microvee filter• Dust filtration up to 5 microns.• For computer rooms, operation theatre etc• Incorporated in central, packaged units

HIGH EFFICIENCY PARTICULATE AIR (HEPA) OR ABSOLUTE FILTERS

SELECTION FACTORS for FILTERS• Flow rate of the filter.• Face velocity of filter ( air in m/s entering the

effective face of filter).• Resistance i.e., difference between static

pressure upstream and downstream specified for clean and dirty conditions.

• Efficiency of filter• Dust holding capacity• Economy, durability and maintenance.• Fire safety.

LOCATION AND INSTALATION OF FILTERS

• Before cooling coil to protect from dust• For high degree filtration two filters - Pre filters at

down stream & regular filter before cooling coil or up stream.

• Avoid fresh air intake through roof surface & from fume and odor.

• Servicing accessibility for filter cleaning • A meter after filter to change or clean filter medium• All ducts should be clean before the filters are

cleaned.• Air tight filter frame to prevent percolation of dust• Door and hatches giving access to live high

voltage conductors of electrostatic precipitator should be equipped with locks.

NON CENTRAL AIR-CONDITIONING UNITS

1. Window air-conditioner (unit ac)

2. Split Air-conditioners

2a) Floor mounted

2b) Wall mounted

2c) Ceiling mounted – (exposed, hidden & cassette type)

WINDOW AIR CONDITIONERS• Compressor, condenser, fan, evaporator, capillary tube in a

single unit• Fixed on any external wall or a window (blocks light partially)• 5 deg slope to exterior is needed for easy flow of condensate

water• Fixing location should serve best possible air circulation• Hermetically sealed (air tight steel shell with compressor and

motor) reciprocating, scroll or rotary type compressor is used• Precaution to be taken for hot air released by condenser• Noisy and no uniform air circulation but economical• Lower level fixing helps in easy maintenance and operation• For narrow / long room - high level installation - better air

circulation• Adjustable grills are provided to direct air movement• Available from 0.5 to 2 TR suitable for 5 to 20 Sqm• Larger spaces to be handled by multiple units• ‘Filter clean reminder’ notice & sleep mode facility

WINDOW AC UNIT

Window Air Conditioner with Electronic Controls

Ideal for large-size rooms up to 1672 square feet, delivers a 2TR cooling capacity and an energy-efficiency rating of 9.4electronic controls - full-function remote capabilities, simple to operate, variable-speed fan, multiple air direction, energy saver and sleep modes, 24-hour on/off timer, and auto cool offer a filter-check reminder and clean-air features

WINDOW AC UNIT AND COOLING CYCLEFor every sq m 200 btu (0.6 TR) is needed as a thumb rule

PARTS OF WINDOW AC UNIT

WINDOW AC UNIT

WINDOW AC UNITAdvantages-• Each room can be controlled with required

humidity & temperature.• Ducts are eliminated• No plumbing work needed.• Simple, low cost & easy to installDisadvantages-• Noisy & servicing is needed• Requires an external window• Occupies space in window• Aesthetically pleasing• Distribution not uniform

WORKING PRINCIPLE OF WINDOW AC AIR CYCLE in Window AC• Evaporator with cooling coil consists of cold

refrigerant• The Fan blows air in to the room through grilles• During this process the air is dehumidified to

some extent and moisture is collected in tray• The used air or hot air from the room enters the

unit through filter at the lower portion• This air mixes with outside air and is blown by

fan through evaporator as conditioned air to room

• This conditioned air is used by the occupants for comfort and the air cycle repeats

REFRIGERATION CYCLE in Window AC• Evaporator - cold refrigerant with low pressure• Air blows over it - cooled - refrigerant becomes hot vapor -

under low pressure• Hot vapor - to compressor - pressure - hot & high pressure

vapor – to condenser coil• Out side air – blow over condenser coil - absorbs heat &

become hot - vapor inside coil - liquid (under high pressure)• High pressure Liquid refrigerant - capillary tube - pressure is

released - becomes cold refrigerant - passed to evaporator• Evaporator - cold refrigerant - air is blown - conditioned,

circulated• Evaporator - air partially dehumidified - water collected in a

tray – to another tray below condenser - evaporates - cools condenser

• Compressor, condenser - outer portion - cools from outside air through fan - position - to reduce the noise to interior

• control panel - controls refrigerant temp - human comfort.

COMPARISON OF UNITARY SYSTEM WITH CENTRAL SYSTEM

UNITARY SYSTEM• Saves installation and labour• Reqd temp of each room is met• Zoning, distribution, duct

eliminatd• Unit run only where A/C is

needed• Failure restricted to particular

rm.• Easy to A/C the spaces in

phases.• Large area this works out costly• Noise/vibration cannot be

elimintd• Maintenance disturbs the room.

CENTRAL SYSTEM• Installation cost is more• Uniform throughout.• Zoning, Ductwork is a must. • Runs throughout • Failures disturbs all A/C area.• A/C system - worked out -

including future expansion• Economical for large areas• Remote plant rm - eliminate

noise, vibration• Easy maintenance

SPLIT AIR-CONDITIONING UNIT• Two units - indoor unit (IDU) & outdoor unit (ODU)• IDU & ODU – linked by refrigeration tubing &

electrical cables• ODU can be mounted outside the room• ODU - condenser, fan, compressor -reduce noise• IDU - evaporator and blower fan• Available up to 5TR• Many advantages over window unit

Non-availability of suitable window or external wall, noisy interior etc

SPLIT AIR-CONDITIONING UNIT• Multiple units to cool 2 or 3 adjacent rooms• Fits well to the interior aesthetics• occupies space for ODU• Frequent operation of doors may bring fresh air

but not desirable for large spaces• Best for executive cabins, show rooms, noise

less commercial spaces etc• Hermetically sealed (air tight steel shell with

compressor and motor) reciprocating, scroll or rotary type compressor is used

SPLIT UNIT

SPLIT AIR-CONDITIONING UNITPiping between IDU & ODUEnsure right distance between the two units, if increased the

disadvantages are,• The refrigerant pressure drops and decreases cooling

capacity• The lubricant oil does not return to compressor &

damages the compressor. (Provide oil trap at every 3m in suction line)

• Extra un-evaporated refrigerant in long tube flows back & damages the compressor

• Insulation cost increases for refrigerant pipingADVANTAGES• Elegant look, Add beauty to the interior• Reduces noise level, Easy maintenance• Electronic control – precise, sleek, accurate control, saves

power

CONDENSATE WATER IN SPLIT UNITS• Evaporator - moisture of the air accumulates as water• Collected in a pan and drained out by gravity / pump,

slope neededMOUNTING OUTDOOR UNIT• Good air circulation - open space – good air movement -

close to IDU• Support and structural care – servicing - railing, safety

measures • locations - plinth protection, over sunshade, terrace, wall

with supports Care for ODU coastal regions• Avoid - condenser fan facing sea wind – reduce speed• Avoid - close to ground - sand dust clogging the

condenser coils• Supports coated with anticorrosive paint • Switch, electrical components - protected from moisture

SPLIT AIR-CONDITIONING UNIT TYPES

Floor mounted

Wall mounted

Ceiling mounted

Exposed type

Hidden type

Cassette type

FLOOR MOUNTEDon floor or a platform - elegant unit with grills Air throw is upwards - affect the furniture layout Occupies floor space - not very user friendly

FLOOR MOUNTED

WALL MOUNTEDFixed above 2m over wall - Control by cord or cordless remote - Saves floor space, Ideal for congested rooms - Most widely used type

WALL & FLOOR MOUNTED UNIT

WALL & FLOOR

MOUNTED UNIT

WALL MOUNTED UNITS

CEILING MOUNTED – EXPOSED• Directly fixed to the ceiling - resembles floor mounted type

but in ceiling• Easy to fix - No false ceiling - Cord or cordless remote

unit for control• Turbo splits are large type units (5TR) to cover large

areasCEILING MOUNTED – HIDDEN• Hidden in a box like unit or false ceiling - Additional cost -

Interior looks bright and uniform - Cord or cordless remote unit for control

CEILING MOUNTED – CASSETTE• Mounted above false ceiling - Outlet grill flush with

surface of false ceiling - Cord or cordless remote unit for control

• Slim, occupies less space - placed directly above the required area

• Multiple units - for larger spaces• A small motorized pump to drain out condensate water

SPLIT UNITS

CEILING MOUNTED

UNITS

CEILING MOUNTED

The cold side, consisting of the expansion valve and the cold coil, is generally placed into a air handler. The air handler blows air through the coil and routes the air throughout the building using a series of ducts. The hot side, known as the condensing unit, lives outside the building.

A split-Ductable system air conditioner splits the hot side from the cold side of the system

REFRIGERATION CYCLE IN PACKAGE UNIT

FLOOR MOUNTED PACKAGE UNIT

DX SYSTEM

CENTRAL AC – CHILLED WATER SYSTEM AC PLANT ROOM WATER COOLED CONDENSER AHU ROOMS PLENUM / FC