Centrifugal Fan Class IV - Greenheck Fan Corporation - Building ...

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High Temperature Operating Limits 4 Temperature Material Arrangement Includes Options -20 to 200°F Steel, Alum., SS 1,4 & 8 None 201 to 500°F 501 to 750°F Steel, Stainless Steel Aluminum limited to 250°F Steel, Stainless Steel Motor Starting Torque 1 & 8 1 & 8 - Heat Slinger - High Temp. Paint - Heat Slinger - High Temp. grease - High Temp. Paint When selecting a motor for a centrifugal fan, the motor must be capable not only of driving the fan at operating speed, but also must be capable of accelerating the fan wheel, shaft and drive to the operating speed. The fan performance tables and curves in this catalog show the brake horsepower required to operate the fan once it is brought to speed. For applications requiring a large air volume at a low static pressure, the BHP required at the fan’s operating RPM may not be sufficient to initially start the fan. If the time required to bring the fan to speed is excessive, the motor winding insulation can be damaged due to excessive temperature rise and the life of the motor seriously affected. For a belt drive centrifugal fan the required motor starting torque capability can be expressed by the following formula: WR 2 M = WR 2 F x ( MRPM) FRPM 2 x (1.1) WR 2 M = The moment of inertia that the motor must be capable of turning at the motor shaft, LB-Ft. 2 WR 2 F = The moment of inertia of the fan wheel, LB-Ft. 2 FRPM = Fan RPM MRPM = Motor RPM For a direct drive fan, WR 2 M must exceed WR 2 F Effect of Air Density - High Suction at Fan Inlet Fan RPM Limitations The maximum allowable wheel RPM shown on the fan performance pages are for fans of standard steel operating at 70°F. Since the strength of the fan wheel, shaft and bearings decrease with an increase in temperature, maximum allowable speeds must be reduced by the correction factors shown below. RPM Correction Factors For High Temperatures Temperature Wheel Material (Degrees F) Aluminum Steel 316 SS 70 1.00 1.00 1.00 200 1.00 .97 .92 250 .95 .96 .89 300 .95 .87 400 .93 .83 500 .90 .80 600 .85 .77 700 .80 .75 800 .72 Moments of Inertia (Lb-Ft 2 ) Moments of inertia are shown for steel wheels with 100% wheel width. Aluminum wheels are approximately 40% of the value shown. STEEL BACKWARD INCLINED CENTRIFUGAL WHEELS Fan Size Class IV Single Width 18 17 20 24 22 40 24 66 27 94 30 143 33 210 36 377 40 581 44 869 49 1350 54 2025 60 3893 66 5511 73 7942 The density used for fan selection is that which is measured at the fan inlet. When the inlet total pressure exceeds 10" in suction, the density at the fan inlet should be corrected by the following values. These values should be multiplied to the fan static pressure and the result used for the proper fan selection. With suction pressures less than 10 in., this correction is typically ignored. Inlet P t Suction D.C.F. -10" 1.03 -14" 1.04 -18" 1.05 -22" 1.06 EXAMPLE 10 in. Ps x 1.03 = 10.3 in. Corrected Ps. Use 10.3 in. Ps to select fan in performance pages. GREENHECK ®
Effect of Air Density - Temperature and Elevation Ratings in the fan performance tables and curves of this catalog are based on standard air (clean, dry air with a density of .075 pounds per cubic foot, barometric pressure at sea level of 29.92 inches of mercury, temperature of 70°F.). Selecting a fan to operate at conditions other than standard air requires an adjustment to both static pressure and brake horsepower. A cubic foot of air has a constant volume regardless of temperature or elevation. However, air density changes with non-standard temperature or elevation. Therefore, when selecting a fan to operate at a non-standard air density using standard air density tables and curves, corrections must be made to parameters affected by air density. These parameters are static pressure and brake horsepower. For example, a size 30 BISW centrifugal fan is to deliver 17,750 CFM at 10.0 in. static pressure. Elevation is 3000 feet, temperature is 150°F. The 10.0 in. static pressure refers to the 0 50 0.87 0.96 0.90 1.00 0.94 1.04 0.97 1.08 1.01 1.11 1.05 1.15 1.08 1.20 1.13 1.24 1.17 1.30 1.22 1.34 1.26 1.40 1.31 1.45 1.37 1.51 1.43 1.57 1.48 1.63 1.54 1.70 static pressure at the operating air density, in this case at 3000 feet, 70 100 1.00 1.06 1.04 1.10 1.08 1.14 1.12 1.18 1.16 1.22 1.22 1.27 1.25 1.32 1.30 1.37 1.35 1.42 1.40 1.48 1.45 1.54 1.51 1.60 1.57 1.66 1.64 1.74 1.70 1.80 1.77 1.88 150°F. Intuitively, we 150 1.15 1.19 1.24 1.30 1.33 1.38 1.44 1.49 1.55 1.61 1.67 1.74 1.81 1.89 1.96 2.04 realize that at higher than standard 200 1.25 1.29 1.34 1.40 1.44 1.50 1.56 1.61 1.68 1.75 1.81 1.89 1.96 2.05 2.13 2.21 elevations and 250 1.34 1.39 1.44 1.50 1.55 1.61 1.67 1.74 1.80 1.88 1.95 2.02 2.10 2.20 2.28 2.37 temperatures, air density will be lower than standard. 300 350 1.43 1.53 1.49 1.58 1.54 1.64 1.60 1.71 1.66 1.77 1.72 1.84 1.79 1.91 1.86 1.98 1.93 2.06 2.01 2.14 2.08 2.22 2.16 2.31 2.25 2.40 2.35 2.51 2.43 2.60 2.53 2.71 Therefore, we must determine what static pressure at standard air 400 500 1.62 1.81 1.68 1.88 1.75 1.95 1.81 2.02 1.88 2.10 1.94 2.18 2.03 2.26 2.09 2.35 2.19 2.44 2.27 2.54 2.37 2.63 2.45 2.73 2.54 2.84 2.66 2.97 2.75 3.08 2.87 3.20 density will equate to 600 2.00 2.07 2.15 2.23 2.31 2.40 2.50 2.59 2.69 2.84 2.91 3.02 3.14 3.28 3.40 3.54 10.0 in. static pressure at our operating density. Since standard air 700 800 2.19 2.38 2.27 2.48 2.35 2.57 2.44 2.67 2.53 2.76 2.63 2.86 2.73 2.98 2.83 3.09 2.94 3.21 3.07 3.33 3.17 3.45 3.31 3.59 3.44 3.74 3.59 3.90 3.72 4.05 3.88 4.21 density is greater than operating air density in this case, we would expect the corrected 900 1000 2.56 2.76 2.66 2.87 2.76 2.989 2.87 3.09 2.97 3.20 3.07 3.31 3.20 3.45 3.33 3.59 3.46 3.73 3.58 3.86 3.71 4.00 3.87 4.17 4.02 4.33 4.20 4.53 4.35 4.69 4.53 4.89 static pressure to be greater than the operating static pressure. The accompanying table gives air density correction factors for non-standard temperatures and elevations. The example below shows the relationship of fan performance at sea level and at 3000 ft. elevation and 150°F. EXAMPLE Air Temp. °F The following example shows how to properly select the fan described above: 1. Since the air volume delivered by the fan is not affected by density, airflow remains 17,750 CFM. 2. Determine correction factor from chart for an elevation of 3000 feet and air temperature of 150°F. The correction factor is 1.30. 3. Multiply the specified operating static pressure by the correction factor to determine the standard air density equivalent static pressure (Corrected static pressure = 10.0 in. x 1.30 = 13.0 in. Ps). 4. Refer to the fan performance table for a 30 BISW. At 17,750 CFM and 13.0 in. Ps: Fan RPM = 2012, BHP = 49.8. 5. 2012 Fan RPM is required to produce the desired performance. 6. Since the horsepower selected refers to standard air density, this must be corrected to reflect actual BHP at the lighter operating air. Operating BHP = standard BHP ÷ 1.30, or 49.8 ÷ 1.30 = 38.3 BHP. If a fan is selected to operate at high temperatures, the motor must be of sufficient horsepower to handle the increased load at any lower operating temperature where the air is more dense. Assume the air entering the 30 BISW fan at start-up is 0°F. For 0°F and 3000 feet elevation the air density correction factor is 0.97. BHP at 0°F = 49.8 ÷ 0.97 = 51.3, therefore, a 75 HP motor is required. AIR DENSITY CORRECTION FACTORS Elevation (Feet Above Sea Level) 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 Ps 25 20 15 10 5 49.8 BHP 10.0 in. Ps Sea Level, 70 - Static Pressure Sea Level, 70 - BHP 3000 ft., 150 - Static Pressure 3000 ft., 150 - BHP 17,750 CFM 38.3 BHP 13.0 in. Ps 0 10 0 5 10 15 20 25 30 35 40 CFM x 1000 60 50 40 30 20 BHP GREENHECK ® 5
Page 1 and 2: CENTRIFUGAL FAN FAN CLASS IV CATALO
Page 3: Motor Selection Greenheck centrifug
Page 7 and 8: Sound Performance Data AMCA License
Page 9 and 10: Belt Drive Fan Selection Procedure
Page 11 and 12: 18 BISW Performance Data Wheel Diam
Page 27 and 28: 33 BISWD 36 BISWD Pressure Class Li
Page 33 and 34: Direct Drive Sound Data Sound Power
Page 35 and 36: Sizes 30-49 Arrangement 4 Size Size

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