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Fan Laws and Application |
Formulas For Fan Applications

How to Use the Fan Laws for Performance Changes
There are two reasons why a fan’s performance may need to be changed:
When these situations occur, it is important to understand how they can affect the fan’s performance.
The effect on the fan’s performance can be shown by using the Fan Laws, shown below

Subscript 1 = existing conditions
Subscript 2 = new conditions
SYSTEM CURVE EQUATION
The following formula is used to find other points on the system line when SP1 and CFM1 are known. Most, but not
all, systems follow this relationship.

IMPORTANT NOTE:
The new RPM should be checked to make sure it does not exceed the maximum allowable RPM for the fan that is installed.