S2 uses a backwardly inclined centrifugal blower wheel. The unit is arrangement 10 and is belt driven by a 3450 RPM TEFC motor. S3 through S5 uses an airfoil blade design for most efficient and quiet operation. The unit is arrangement 10 and is belt driven with an 1800 RPM TEFC motor. Factory dynamically balanced and checked against the acceptable levels on the Rathbone Chart.
Standard coating is an industrial baked enamel.