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Fan

Selection

Fan

capacity rating

tables

are

based

on

standard air

at

70°F

and

sea

level elevation. For other

operating

conditions,

correct

the

Static

Pressure

(SP)

before

using

the

rating

tables. The Brake

Horsepower

(BHP)

is corrected

after

the

fan

selection

has been made.

Finally

determine

fan

class

by

comparing

the

fan

selection

RPM

to

the maximum

safe

speeds

listed

for

each class

in

the table

on

page

17.

EXAMPLE:

Select

a

Design

95

fan

to

handle

18,000

CFM

at

9”

SP.

Temperature

is

600°F

and the

installation site is

500

feet

above

sea

level.

1.

Refer

to

Table

I.

At

500

feet

and

600°F

the

correction

factor

is

2.04.

To

simplify

the

calculations,

use

2.00.

The corrected

SP

is

2.00

X

9”

SP

=

18”

SP for

70°F

and

sea

level.

2.

Using

the

fan

rating

tables,

one

fan

selection

for

18,000

CFM

at

18”

SP

is

a

Size

270.

The

fan

will

run

at

2667

RPM

and

require

63.6

BHP

at

70°F

and

sea

level.

(The

actual

RPM

and

BHP

were

calculated

by

interpolating

between the

17,212

and

18,1

68

CFM

values

given

in

the

rating

table).

3.

Correct

the

BHP.

Dividing

63.6

by

the correction

factor from

step

1

(2.00).

63.6

=

2.00

=

31.8

BHP

at

600°F

and

500

feet

elevation.

4.

To determine

fan

class the wheel

must

be

checked

for

maximum

RPM

using

the Fan Data

table

on

page

17

and the

Speed

Deration

factors

inTable

II

at

right.

a.

Divide

fan

operating

RPM

by

the

Speed

Deration

factor for

600°F found

in

Table

II.

Wheel

RPM

at

70°F

is

2667 .88

=

3031.

b.

For

a

belt

drive

fan

divide the

fan

operating

RPM

by

the

Shaft

Deration

factor for 600°F

found

in

Table

II.

Shaft

RPM

at

70°F

is

2667

=

0.96

=

2778.

c.

Check

the Fan Data table

on

page

17

for

maximum wheel

RPM

for

a

Size

270

fan.

The

required

wheel

RPM

of

3031

is

within

the limits

of

Class

IV.

d.

For

a

belt drive

fan,

check the

Fan Data

table

on

page

17

for

maximum

shaft

RPM

for

a

Size

270

Fan. The

required

shaft

RPM

of

2778

is

also

within

the

limits

of

Class

IV.

e.

Both the wheel and

shaft

are

within

the

Class

IV

RPM

limit.

The

required

fan

construction

is

Class

IV.

NOTE:

For Direct Drive

fans

the maximum

shaft

RPM

listed

are

at motor

synchronous

speeds

at

60

Hz

power.

Those

speeds

do

not

need

to

be checked since

they

are

already

sized

for

the

max

temp

of 800°F.

TABLE I

-

TEMPERATURE

AND

ALTITUDE

CORRECTION

ALTITUDE

(FT)

AND

BAROMETRIC

PRESSURE

(IN HG)

TEMP

(°F)

0

FT

29.92

500

FT

29.38

1000

FT

28.86

1500

FT

28.33

2000

FT

27.82

2500

FT

27.31

3000

FT

26.82

3500

FT

26.32

4000

FT

25.84

5000

FT

24.90

-15

0.79 0.81 0.82 0.84 0.85 0.87 0.88 0.90 0.96 1.00

0

0.87 0.88 0.90 0.92

0.93

0.95 0.97 0.99 1.00 1.04

70

1.00 1.02 1.04 1.06 1.08 1.10

1.12 1.14

1.16 1.20

100

1.06 1.08 1.10

1.12 1.14

1.16 1.18 1.20

1.22

1.27

150 1.15

1.17

1.19

1.22 1.24

1.26 1.28

1.31 1.33 1.38

200 1.25

1.27

1.29

1.32 1.34 1.36 1.39

1.42 1.44

1.50

250

1.34 1.36

1.39

1.41 1.44 1.47

1.49

1.52

1.55

1.61

300 1.43

1.46 1.49 1.51 1.54 1.57 1.60

1.63

1.66

1.72

350

1.53

1.56 1.58 1.61 1.64 1.67 1.70

1.74 1.77

1.84

400 1.62 1.65 1.68

1.71

1.75 1.78

1.81

1.84

1.88

1.95

500 1.81 1.84 1.88 1.91 1.95 1.98 2.02 2.06 2.10 2.18

600

2.00 2.04 2.07

2.11

2.15 2.19

2.23

2.27

2.32

2.40

650 2.09

2.13

2.17 2.21

2.25 2.29

2.34 2.38 2.43

2.52

700 2.19

2.23

2.27

2.31 2.35

2.40

2.44

2.49

2.53 2.63

800

2.38

2.42

2.48

2.51

2.56 2.60 2.65 2.70 2.75 2.86

TABLE II

-

SPEED

DERATION

TEMP

(°F)

WHEEL

ALL

CL.

SHAFT

ALL

CL.

-15

1.00

1.00

0

1.00

1.00

70

1.00

1.00

100

0.99

1.00

150

0.96

1.00

200

0.95

0.99

250

0.95

0.98

300

0.94

0.98

350

0.93

0.97

400

0.92

0.97

500

0.90

0.96

600

0.88

0.96

650

0.87

0.95

700

0.86

0.94

800

0.83

0.93

Percent

width

selections

are

also

available

for

the

Design

95.

Refer

to

Chicago

Blower’s

fan.net

selection

software for

exact

selections.

Refer

to

Chicago

Blower’s

fan.net

for

performance,

fan

curves

and sound data.

For

software

and

assistance,

visit

www.ChicagoBlower.com

7