Hvac Load Calculation PDF
Hvac Load Calculation PDF
Hvac Load Calculation PDF
Split AC
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
more commonly a window sill.
The split air conditioner comprises of two parts: the outdoor unit and the indoor unit. The outdoor
unit, fitted outside the room, houses 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.
The central air conditioning plants or the systems are used when large buildings, hotels, theaters,
airports, shopping malls etc are to be air conditioned completely. The window and split air
conditioners are used for single rooms or small office spaces. If the whole building is to be cooled it is
not economically viable to put window or split air conditioner in each and every room. Further, these
small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc.
Central air conditioning 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 making this a better option. A 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.
THERMAL COMFORT
1999 ASHRAE Applications Handbook (SI)
General Design Criteria
General Category Specific Category Inside Design Conditions Air Movement Circulation,
Winter Summer air changes per hour
Dining Cafeterias and 21 to 23°C 26°C e 0.25 m/s at 1.8 m 12 to 15
and Luncheonettes 20 to 30% rh 50% rh above floor
Entertainment
Centers Restaurants 21 to 23°C 23 to 26°C 0.13 to 0.15 m/s 8 to 12
20 to 30% rh 55 to 60% rh
Climate
For the classification purpose these can be categorized as follows
Orientation
•Latitude
Internal Loads
Lighting
Occupants
Equipment
Humidification and
dehumidification
External loads
Fenestration
Infiltration
Building envelope
Ventilation Loads
The air flow rates for ventilation
purposes
HVAC LOAD CALCULATION METHODS
Rule-of-thumb sizing
One ton of cooling equipment for every 400 square feet of conditioned space. In a concession to recent
improvements in insulation levels and window specifications, some HVAC contractors have adjusted their
rule of thumb, and now size air conditions at one ton per 600 square feet.
One ton of cooling per 1,000 square feet. According to Blasnik, “Sizing an air conditioner using tons per
square foot actually works pretty well, as long as you choose the right rule of thumb.”
ADVANTAGES DISVANTAGES
NOTES
1. Rule of thumb to size an air conditioner is no substitute for performing a room-by-room cooling load calculation.
2. Room-by-room calculations are necessary for many reasons: to properly size ductwork, for example, and to
address unusual architectural features like rooms with large west-facing windows.
HVAC LOAD CALCULATION METHODS
Software Programs
The physics involved in the transfer of heat and energy between buildings, occupants, and the environment is quite complex.
The most current and best math models of this problem require significant input data and thousands of calculations in an
iterative process.
ASHRAE has TETD (Total Equivalent Temperature Difference), CLTD (Cooling Load Temperature Difference), TFM
(Transfer Function Method), HB (Heat Balance) and RTS (Radiant Time Series).
INITIAL HVAC LOAD CALCULATION
URBAN DESIGN PROBLEM MAHINDRA SEZ
DESIGN BRIEF
Software
7500 12000 10500 30000 3900000
development block
Food Court 2000 3200 2800 8000 360000
Education &
0 0 3000 3000 300000
Research Block
Employee Care
150 0 150 300 162000
Centre
Support Staff 100 160 140 400
Parking- Cars 1575 2520 2205 6300 (no.)
Parking- Two
675 1080 945 2700 (no.)
Wheelers
Software
development block 3900000
÷ 30000
= 130 sq.ft./person x 7500 = 975000
Education &
Research Block 300000
÷ 3000 = 100 sq.ft./person x 0 = 0
Employee Care
Centre 162000 ÷ 300
= 540 sq.ft./person
x 150 = 81000
Applying rule of thumb : one ton of cooling per 1,000 square feet
Total HVAC cooling Load = 584.46 ton= 85 kwhr ( 1 ton=3.5kw )
was one ton of cooling equipment for every 400 square
feet of conditioned space. In a concession to recent
improvements in insulation levels and window
specifications, some HVAC contractors have adjusted their
rule of thumb, and now size air conditions at one ton per
600 square feet.