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.
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