Fan Laws & Unit Conversions
Fan Laws
Commonly Used Units
Volume varies directly as speed:
New CFM = Old CFM x New RPM/Old RPM
Horsepower varies as cube of speed:
New HP = Old HP x (New RPM/Old RPM)3
Pressure varies as square of speed:
New SP = Old SP x (New RPM/Old RPM)2
Pressure varies as square of volume:
New SP = Old SP x (New CFM/Old CFM)2
Horsepower varies as curb of volume
New HP = Old HP x (New CFM/Old CRM)3
Pressure
In WG (std English)
Pascals (std Metric)
Psi
In. Hg
mm WG
Atm
Volume Flow
In WG (std English)
Pascals (std Metric)
Psi
In. Hg
mm WG
Atm
Velocity
In WG (std English)
Pascals (std Metric)
Psi
In. Hg
mm WG
Atm