Air Conditioning Load calculation

Air Conditioning

Its all about comfort….

Air Conditioning

• Air conditioning is the removal of heat from indoor air for thermal comfort.

• In another sense, the term can refer to any form of cooling, heating, ventilation, or disinfection that modifies the condition of air.

Air Conditioner

• An air conditioner (often referred to as AC) is a home appliance, system,or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle. In construction, a complete system of heating, ventilation and air conditioning is referred to as "HVAC".

Types of Air Conditioners

• Window AC System• Split AC System• Packaged AC System• Central AC System

Window AC System

• Window air conditioner is the most commonly used air conditioner for single rooms.

• In this air conditioner all the components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a single box.

• This unit is fitted in a slot made in the wall of the room, or often a window sill.

Split AC System

• The Split air conditioner comprises of two parts:1) Outdoor unit 2) Indoor unit • The outdoor unit, fitted outside the room, has

components like the compressor, condenser and expansion valve.

• The indoor unit comprises the evaporator or cooling coil and the cooling fan.

• For this unit you don’t have to make any slot in the wall of the room. Further, the present day split units have aesthetic looks and add to the beauty of the room. The split air conditioner can be used to cool one or two rooms.

Package AC System

• An HVAC designer will suggest this type of air conditioner if you want to cool more than two rooms or a larger space at your home or office.

• All the components, namely the compressor, condenser (which can be air cooled or water cooled), expansion valve and evaporator are housed in a single box. The cooled air is thrown by the high capacity blower, and it flows through the ducts laid through various rooms.

Central AC System

• The central air conditioning system is used for cooling big buildings, houses, offices, entire hotels, gyms, movie theaters, factories etc.

• If the whole building is to be air conditioned, HVAC engineers find that putting individual units in each of the rooms is very expensive initially as well in the long run.

• The central air conditioning system is comprised of a huge compressor that has the capacity to produce hundreds of tons of air conditioning.

• Cooling big halls, malls, huge spaces, galleries etc is usually only feasible with central conditioning units.

ACBuilding

ExhaustFan

Return Air

Fresh Air

ExhaustAir

Cooling Load Calculation

• A building or room gains heat from many sources. • Inside occupants, computers, copiers, machinery, and lighting

all produce heat. • Warm air from outside enters through open doors and

windows, or as ‘leakage’ though the structure. • However the biggest source of heat is solar radiation from the

sun, beating down on the roof and walls, and pouring through the windows, heating internal surfaces.

• The sum of all these heat sources is know as the heat gain (or heat load) of the building, and is expressed either in BTU (British Thermal Units) or kW (Kilowatts).


• For an air conditioner to cool a room or building its output must be greater than the heat gain. It is important before purchasing an air conditioner that a cooling load calculation is performed to ensure it is big enough for the intended application.

The heat gain of a room or building depends on:

1) The size of the area being cooled.

2) Size and position of windows, and whether they have shading.

3) Number of occupants.

4) Generated by equipment and machinery.

5) Generated by lighting .

By calculating the heat gain from each individual item and adding them together, an accurate cooling load figure can be determined.



Step One

Calculate the area in square feet of the space to be cooled, and multiply by 31.25

Area BTU = length (ft.) x width (ft.) x 31.25

Cooling Load CalculationStep Two

Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4.

North window BTU = Area of North facing windows (m. sq.) x 164

If no shading, North window BTU = North window BTU x 1.4

South window BTU = Area of South facing windows (m. sq.) x 868

If no shading, South window BTU = South window BTU x 1.4 Add the results together.

Total window BTU = North window + South window


Step ThreeCalculate the heat generated by occupants, allow 600 BTU per person.

Occupant BTU = number of people x 600

Step Four

Calculate the heat generated by each item of machinery - copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4

Equipment BTU = total equipment watts x 3.4


Step Five

Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25

Lighting BTU = total lighting watts x 4.25

Step SixAdd the above together to find the total heat load.

Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU


Step SevenFinally, find the total heat load in Tons of Air conditioning according to the following relationship.

1 Ton = 12,000 BTU

Total heat load in Tons = Total heat load BTU12,000

AC Selection• If your load doesn’t come out to be a fix quantity• Then you shall select the AC with higher capacity than calculated

load. e.g.• If your load comes out to be 1.8 Tons which is more than 1.5 Tons,

so you shall buy 2 Tons AC to fulfill your requirements.• When you bought your AC, so sit down relax & Just Chill in month of

June-July-August in Peshawar….

• Coz it’s all about comfort….

Documents

Air Conditioning Load calculation