Fan Fundamentals
Introduction to FAN SELECTION
This is a guide to the most basic fan sections, all of which enable you to select the right fan for the job. It will answer the following questions (and more):
•What is a SONE?
•How are model numbers and performance tables used to select a fan?
•How are direct drive and belt driven fans different?
•What types of motors are used with these fans?
The goal is to understand and use the Greenheck literature as an important tool in filling a customer’s fan order.
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cfm | Cubic Feet Per Minute. A measure of airflow. | |
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Ps | Static Pressure. Resistance to airflow measured in inches of water gauge. | |
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sone | A measure of loudness. One sone can be approximated as the loudness of a quiet refrigerator at a distance of 5 feet. Sones | |
follow a linear scale, that is, 10 sones are twice as loud as 5 sones. | ||
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Bhp | Brake Horsepower. A measure of power consumption. Used to determine the proper motor horsepower and wiring. | |
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hp | Horsepower. Used to indicate a fan’s motor size. | |
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rpm | Revolutions Per Minute. Measure of fan speed. | |
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TS | Tip Speed. The speed of the tip of a fan wheel or prop measured in feet per minute. | |
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AMCA | Air Movement & Control Association. A nationally recognized association which establishes standards for fan testing and | |
performance ratings. AMCA also license air volume and sound certified ratings. | ||
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Model Designation
For Greenheck belt drive models, the model designation tells the model type, size and the motor hp.
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Model is GB |
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| hp is 1/6 |
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Nominal Wheel Dia. 9 in. | |||||
For direct drive units, the model designation tells the model type, the size and the motor/fan rpm.
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Model is G |
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| rpm is 1140 |
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Nominal Wheel Dia. 12 in. | |||||
BELT DRIVE | DIRECT DRIVE | ||
Suffix | Motor hp | Suffix | Fan rpm |
6 | 1/6 | A | 1725 |
4 | 1/4 | B | 1140 |
3 | 1/3 | C | 860 |
5 | 1/2 | D | 1550 |
7 | 3/4 | G | 1300 |
10 | 1 | E | 1050 |
15 | 11/2 | F | 880 |
20 | 2 | P | 1625 |
30 | 3 |
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505
7571/2
This table lists model designation suffixes for motor horsepower and fan rpm.
Motor Information (Belt Drive Only)
When specifying a belt drive fan, the model designation does not completely describe the unit. Additional information about the motor is necessary. These items are listed below:
Motor EnclosureThis will be either “Open” (open, drip proof), “TE” (totally enclosed) or “EXP”
DIRECt Drive
Selection of direct drive fans (those with the motor shaft connected to the fan wheel or propeller) is nearly the same as belt drive selection. However, there are two differences worth noting. Where belt drive fan speed can be altered by adjusting the motor pulley, direct drive fans (since they have no pulleys) must use a different method.
1To adjust a direct drive fan’s speed (also motor speed) or to provide a means of meeting an exact performance requirement, a speed control can be furnished. Speed controls vary the voltage supplied to the fan and slow
it down; a principle similar to the way dimmer light switches work.
2Models CUE and CW, sizes
Motors are available in either
Voltage and phase. Voltage can be 115, 208, 230 or 460. Phase is either
Suffix Letter | Motor Speed | Wiring Connections |
D | 1550 rpm | White to L1 Black to L2 |
G | 1300 rpm | White to L1 Blue to L2 |
E | 1050 rpm | White to L1 Red to L2 |
The three speeds are 1550 rpm (D), 1300 rpm (G) and 1050 rpm (E). Changing a motor lead is all that is necessary to change speeds. When selecting a model with a 3 speed motor, it is recommended that the G speed be chosen whenever possible. This is the middle speed, which gives the greatest flexibility in air volume because airflow can be increased or decreased simply by changing a motor lead.
F A N F U N D A M E N T A L S | 129 |
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