Any accessory that is part of an installation causes a load loss that must be taken into account when calculating an installation.
To calculate the load loss in the accessories, or specific elements of an installation, we will use the coefficient method. Experimentally, it has been concluded that the overall loss caused by an accessory is proportional to the speed of the air passing through it. Therefore, it can be expressed as a function of the dynamic pressure of the duct multiplied by said factor. This consists of determining the loss by means of a proportionality factor.
In the following document you will discover how to do this calculation and what are the coefficients applicable to each accessory.
See how to calculate the load loss caused by an accessory in an installation