ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 25
System static-pressure loss,
in. w.g. (Pa)
7.0
(1,742)
6.0
(1,493)
(l/s)-is represented along the x-axis, while system pres-
5.0
(1,244)
(in. w.g., or in. H2O), Pascals (Pa),1 or millimeters of water
sure loss-typically expressed in inches of water gauge
4.0
(995)
gauge (mm H2O)-is represented along the left y-axis.
In the succeeding examples, the desired airflow and
3.0
(747)
system pressure loss are 12,000 cfm (5.66 m3/s) and 5.0
2.0
(498)
in. w.g. (1,244 Pa), respectively (Figure 1).
1.0
(249)
0.0
(0)
0
2,500 5,000
(0.00) (1.18) (2.36)
Fan Selection
7,500 10,000 12,500 15,000 17,500 20,000
(3.54) (4.72) (5.90) (7.08) (8.26) (9.44)
Whether via the Internet on their website or as a program
to be installed on a user's computer, many fan manufac-
Flow, cfm (m 3/s)
turers offer software capable of quickly identifying a
FIGURE 1. Duty point of 12,000 cfm (5.66 m3 /s) at
5.0-in.-w.g. (1,244 Pa) system pressure loss.
number of possible fan solutions for a given duty point.
Typically, possible fan selections are displayed in a table
alone and would not be lacking company today. While,
showing model type, size, flow, pressure, speed, required
at fi rst glance, a fan curve can appear complicated, it is
power, efficiency, outlet velocity, and other relevant data.
fairly easy to interpret once one gains an understanding
Table 1 shows output from one program for our duty
of the conventions and terminology used. Reading a
point of 12,000 cfm (5.66 m3/s) at 5.0-in.-w.g. (1,244 Pa)
fan curve (correctly) is a skill worth
Type
select and specify fans to understand
GI
Cent. 200AF 20.00 12,000
5.0
6.7
1.7
3,414
21.6
43%
GI
Cent. 240AF 24.50 12,000
5.0
5.7
0.8
2,110
14.1
67%
GI
Cent. 270AF 27.50 12,000
5.0
5.5
0.5
1,621
12.1
78%
GI
Cent. 300AF 30.00 12,000
5.0
5.3
0.3
1,366
11.7
81%
GI
Cent. 330AF 33.00 12,000
5.0
5.2
0.2
1,204
12.0
79%
GI
Cent. 360AF 36.50 12,000
5.0
5.2
0.2
1,067
12.6
75%
GI
Cent. 400AF 40.25 12,000
5.0
5.1
0.1
961
13.6
69%
Flow,
m3/s
Ps ,
Pa
Pt,
Pa
P v,
Pa
S. Eff.,
RPM Power,
kW
%
the performance characteristics and
capabilities of different equipment so
they may determine the fan that best
suits the requirements of an application. For them, this article will help
to straighten out fan curves.
While there is no standard method
for graphically representing fan-performance data, this article will cover what
Size
Dia.
Flow,
Ps ,
Pt,
P v,
Power, S. Eff.,
cfm in. w.g. in. w.g. in. w.g. RPM
bhp
%
possessing, as it allows those who
one is most likely to see.
Type
Size
Dia.
Airflow and Pressure Loss
GI
Cent. 200AF 20.00
5.66
1,238
1,657
419.5
3,414
16.1
43%
In the design of a ventilation system, the
GI
Cent. 240AF 24.50
5.66
1,243
1,431
187.4
2,110
10.5
67%
GI
Cent. 270AF 27.50
5.66
1,244
1,371
127.0
1,621
9.0
78%
GI
Cent. 300AF 30.00
5.66
1,244
1,330
86.2
1,366
8.7
81%
As stated earlier, on a fan-curve
GI
330AF 33.00
Cent.
5.66
1,244
1,303
58.7
1,204
9.0
79%
graph, airflow-typically expressed
GI
Cent. 360AF 36.50
5.66
1,244
1,283
39.2
1,067
9.4
75%
GI
Cent. 400AF 40.25
5.66
1,244
1,271
26.5
961
10.2
69%
desired airflow rate and system pressure loss (static pressure or total pressure) often are referred to as the duty
point. A fan curve depicts duty point.
in cubic feet per minute (cfm), cubic
meters per second (m3/s),1 cubic meters
per hour (m3/h), or liters per second
w w w. a m c a .o r g
TABLE 1. Typical fan-selection table.
2020 A M CA i n m o t i o n
25
http://www.amca.org
ASHRAE Journal Supplement - AMCA InMotion - October 2020
Table of Contents for the Digital Edition of ASHRAE Journal Supplement - AMCA InMotion - October 2020
Contents
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - BB1
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - BB2
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - Cover1
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - Cover2
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - Contents
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 2
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 3
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 4
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 5
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 6
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 7
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 8
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 9
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 10
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 11
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 12
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 13
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 14
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 15
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 16
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 17
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 18
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 19
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 20
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 21
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 22
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 23
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 24
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 25
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 26
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 27
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 28
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 29
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 30
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 31
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 32
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 33
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 34
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 35
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 36
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 37
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 38
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 39
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 40
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 41
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 42
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 43
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - 44
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - Cover3
ASHRAE Journal Supplement - AMCA InMotion - October 2020 - Cover4
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