Greenheck Fan 129 User Manual

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.

TERMS

cfm Cubic Feet Per Minute. A measure of airflow.

Ps Static Pressure. Resistance to airflow measured in inches of water gauge.

sone

Bhp Brake Horsepower. A measure of power consumption. Used to determine the proper motor horsepower and wiring.

hp Horsepower. Used to indicate a fan’s motor size.

rpm Revolutions Per Minute. Measure of fan speed.

TS Tip Speed. The speed of the tip of a fan wheel or prop measured in feet per minute.

AMCA

MODEL DESIGNATION

For Greenheck belt drive models, the model designation
tells the model type, size and the motor hp.

EXAMPLE: GB-090-6

Model is GB hp is 1/6
Nominal Wheel Dia. 9 in.

For direct drive units, the model designation tells
the model type, the size and the motor/fan rpm.

EXAMPLE: G-121-B

Model is G rpm is 1140
Nominal Wheel Dia. 12 in.

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 ENCLOSURE

This will be either “Open” (open, drip proof), “TE” (totally
enclosed) or “EXP” (explosion-resistant). Open is the
most common and will be supplied unless otherwise
specified.

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.

1

Models CUE and CW, sizes 060-095 and Model SQ,

2

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.

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.

BELT DRIVE DIRECT DRIVE

Suffix Motor hp Suffix Fan rpm

6
4 ¼ B 1140
3
5 ½ D 1550

7 ¾ G 1300
10 1 E 1050
15 1½ F 880
20 2 P 1625
30 3
50 5
75 7½

1

/

6

1

/

3

A 1725

C 860

This table
lists model
designation
suffixes for motor
horsepower and
fan rpm.

SPEEDS

Motors are available in either single-speed or two speed.
Single-speed motors are 1725 rpm. Two speed motors
will be 1725/1140 rpm. Single-speed will be supplied
unless otherwise specified.

ELECTRICAL CHARACTERISTICS

Voltage and phase. Voltage can be 115, 208, 230 or 460.
Phase is either single-or 3 phase. A 115 volt, single­phase motor is shown as 115/1. Typically, motors of
1/2 hp and less are single-phase. Motors of 3/4 hp and
greater are 3 phase.

TYPICAL MOTOR TAG - Electrical Instructions

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

To 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.

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.

sizes 60-95, are provided with 115 volt, 60 cycle motors.

FAN FUNDAMENTAlS

129

Introduction to FAN SELECTION

MOTOR HORSEPOWER

The motor horsepower for direct drive fans is
always sized by Greenheck and does not require
further consideration. For belt drive models,
the catalog identifies which horsepower is
recommended. However, there are times when it
is wise to bump the horsepower one size. For
example, the hp recommended for the GB-180
at 810 rpm (2375 cfm @ .5” Ps) is 1/3 hp.

Although a 1/3 hp motor is recommended, it is
not necessarily a good motor selection for this
application. Our static pressure of 0.5 in. was only
an estimate. It may actually turn out to be .625 in.

BELT DRIVE

One advantage of choosing a belt drive over a direct
drive is that it is capable of adjusting the fan rpm,
which enables the fan to move more air if necessary.

If this is the case, we will need a 1/2 hp motor
because our fan will have to run at almost
810 rpm (refer to performance box - 2052 cfm at

0.625 in. Ps). Therefore, choosing a 1/2 hp motor
in this case is exercising good judgement.

The complete model designation for this
application is GB-180-5.

NOTE: The GB-180-5 has an rpm range of 700-940.
This means that if the static pressure is less than
estimated, say 0.25 in. Ps, the fan can be slowed down
to accommodate this condition.

Motor pulleys are adjusted by loosening the set
screw and turning the top half of the pulley (see
illustrations at right). This causes the pulley diameter
to change, which results in changing the fan rpm.

APPLICATIONS

Ventilating a building simply replaces stale or foul
air with clean, fresh air. Although the ventilation
process is required for many different applications,
the airflow fundamentals never change:

UNDESIRED AIR OUT, FRESH AIR IN

The key variables that do change depending on
applications are the fan model and the air volume
flow rate (cfm). Other considerations include the
resistance to airflow (static pressure or Ps) and
sound produced by the fan (Sones).

Occasionally, a customer will require a fan to perform
a particular function, yet does not know which model
to use or even what cfm is necessary. In this case,
some fan specification work must be done.

Fan specification is usually not a precise science
and can be done confidently when the fan
application is understood.

Based on the application, four parameters need to
be determined. They are:

Fan Model

Cubic Feet per Minute (cfm)

Static Pressure (Ps)

Loudness limit (sones)

Belt

Opening the pulley decreases fan rpm.
Closing the pulley increases fan rpm.

The information that follows will help walk you
through this type of problem and enable you to
select the right fan for the job.

FAN MODEL

Fans all perform the basic function of moving air
from one space to another. But the great diversity of
fan applications creates the need for manufacturers
to develop many different models. Each model has
benefits for certain applications, providing the most
economical means of performing the air movement
function. The trick for most users is sorting through
all of the models available to find one that is
suitable for their needs.

PROPELLER vs. CENTRIFUGAL WHEEL

Propeller fans provide an economical method to
move large air volumes (5,000+ cfm) at low static
pressures (0.50 in. or less). Motors are typically
mounted in the airstream which limits applications to
relatively clean air at maximum temperatures of 110°F.

Centrifugal fans are more efficient at higher static
pressures and are quieter than propeller fans.
Many centrifugal fan models are designed with
motors mounted out of the airstream to ventilate
contaminated and high temperature air.

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FAN FUNDAMENTAlS