Direct-Fired Formulas

Heating Requirements

Input BTU/Hr =   (Blower SCFM * Temp Rise * Density Factor) / .92

Temp Rise =   (Input BTU/Hr * .92) Blower SCFM * Density Factor

Density Factor =   1.08 +  (70-Blower Temp) * .024 10

Output BTU/Hr

Output BTU/Hr =   Input BTU/Hr * .92

Profile Velocity

Profile Velocity =   945 * sqrt(Profile Pressure / 0.075)

Burner Areas

6 Inch Straight = .32 sq ft. 12 Inch Straight = .65 sq ft. T Section = .77 sq ft. Ell Section = .65 sq ft.