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(Developed by Rajeev Kakkar)
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ONLINE HEAT LOAD| Keep the following information handy: (All dimensions are in feet or square feet, as this is the common units for load estimation. (If you have the dimensions in meters, please convert to feet by multiplying meters by 3.28.) |
| The Length, Breadth and Height of your room or office. |
| The false ceiling height, if you have a false ceiling. |
| The Length of each wall which is exposed to the sun, and its orientation. (You may need a compass for this, or determine the orientation by the position of the sun!) |
| The square feet area (length x height) of partitions (examples are, walls which are not exposed to the sun, and are not adjacent to air-conditioned areas, such as toilet walls, staircases, passages and kitchens). |
| The size of each window (length, height) in each exposed wall, and the number of windows. |
| Note the area of the roof in square feet if it is exposed to the sun, or if the floor above is non-airconditioned. (If the roof is exposed to the sun, it is assumed that the under deck of the roof shall be insulated). |
| Note the area of the floor in square feet, if the floor below is non-airconditioned. |
| The number of persons occupying the space most of the time. |
| The lighting load in watts per sqft. (Total number of tubelights x 40 watts / square feet floor area, or use 1.5 watts per square foot as an average figure.) |
| The number of PCs (Personal Computers) / terminals, if any. |
| The capacity of the UPS in KVA, if you have a UPS. |
The Result gives you;
Both the tons requirement and the air quantiy requirement are equally important in selecting the airconditioner.The selected airconditioner must be able to meet both the tons requirement and the air quantity requirement. Usually, air-conditioners are designed for 400 cfm per 1 ton of air-conditioning.
In the Example Heat Load, the calculated tons is equal to 4.7
tons, and the calculated cfm is equal to 3,328 cfm.
A 5.0 ton ductable split will give (5 tons x 400 cfm=2,000
cfm) 2,000 cfm of air. This air quantity is less than the
requirement of 3,328 cfm. So, add 2 nos. 1.5 ton room airconditioners.
Alternatively, a 7.5 ton ductable split air-conditioner giving (7.5 tons x 400 cfm=3,000 cfm) 3,000 cfm may be used.
You may need to estimate the airconditioning requirements at an
early stage of refurbishing or constructing your home or office
for purposes of:
Estimating your electrical requirements.
Deciding location of airconditioning equipment depending on capacity
and make.
Deciding where wall openings need to be made.
Estimating the budget cost.
While not a professional load calculator, it serves the purposes
mentioned above. It has been simplified, to provide a very good
estimate, not precise results. (Probably not required in any case,
for most estimations). The more accurate the input data, the better
the results.
Example Heat Load.
An office in Mumbai, is of size 20 ft x 40 ft, with a ceiling height of 12 ft.A false ceiling is proposed at 10 ft height.
One 40 ft long wall faces SouthWest, and one 20 ft long wall faces SouthEast.
(Both are exposed to sun. Walls which are not, are considered partitions).
The other two walls are partitions with non-airconditioned offices next to them.
(20ft x 12ft)+(40ft x 12ft )=720 sqft) (Toilet, staircase and passage walls are also partitions).
There are 2 windows on the SouthWest wall, each of size 4 ft x 6 ft.
The roof is exposed to the sun or floor above is non air-conditioned. (20ft x 40ft = 800 sqft)
The floor below is non- airconditioned. (20ft x 40ft = 800 sqft).
Lighting load is taken as 1.5 watts per sqft.
There are 12 persons to be seated in the office.
There are 12 PCs / terminals, one for each person.
There is 1 server.
There is a 5 KVA UPS for emergency.
All the above values have been plugged into the example heat load for your convenience.
Just click the solve button at the lower end of the Example Heat Load page, and read the results.
The percentage distribution of the load is also calculated, to enable you to determine
where energy could best be saved. Click here for the Example Heat Load
After trying the example Heat Load, and gathering the details
for the calculation you wish to make, come back to this page and
click here for the Heat Load.
Your comments are welcome!
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