Air Duct Calculator

Ducts play an important role in your HVAC system to give it the desired level of comfort. If the ducts are not sized properly, chances are high that there will be blockage in the air-flow and the desired level of temperature control will not be achieved. Hence, proper air duct calculation needs to be done before you finally install an HVAC system. However, it needs to be kept in mind that proper air duct calculation can be done only by a professional because it is quite a technical thing and only professionals are aware of the process. So, it is recommended that you get in touch with a reputed HVAC professional for this particular task.

Before we proceed into calculating duct sizes, we need to mention that ducts are of different sizes and each of them has their own set of advantages as well as disadvantages. For example, there are round ducts, rectangular ducts, and oval ducts. Besides different duct shapes, the material used for ducting are also different in different cases. For instance, there are metallic ducts as well as non-metallic ducts.

Now let us have a look at the first step that is involved in air duct calculation. It is the whole house load calculation which is done each room basis. Once that is done, one has to apply a particular formula of Room CFM = (Room Load / Whole House Load) * Equipment CFM. You must keep in mind that it is important to carry out room by room load calculation to find out the CFM that is to be supplied to each room so that the temperature distribution is even throughout the house.

Once the above mentioned step is complete, one of the commonly applied methods for duct size calculation is to taken into account that is the constant friction loss method. It has been noted that ducts in small buildings are sized using the equal friction method or the modified equal friction method. The equal friction method involves maintaining the same pressure drop per unit of duct length throughout the system and the duct size is based on the flow rate through a particular section of the duct, and design value for the friction rate. Generally, duct sizes are calculated using slide rule or a ductilator.

Besides, the constant friction loss method other methods that may be used to calculate the duct sizing include the velocity reduction method and the static regain method.

In recent times there are many software as well which are used as duct calculator. The specialty of these calculators is that they are precise and chances of errors are minimized.



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