AMCA InMotion - September 2019 - 5

Let's consider potential problems related
compliant, it must be sized and selected
for an FEI rating of 1.00 or higher. This
is the threshold that code and standard bodies and regulators appear to
be converging on, although a rebate
program might require an FEI rating of

Static pressure

to compliance. In this case, for a fan to be

1.20 or higher.
Table 1 summarizes the performance
of airfoil and backward-inclined fans of

12

in. wg

3.0

kPa

Compliance Considerations

2.5

10

2.0

8
6

1.5
1.25

Fan curve
System curve

5.0

100%
%

1.0

4

0.5

2

0.0

0

FEI = 1.00

FEI = 0.80

0

3

6

9

12

15

0.0

1.5

3.0

4.5

6.0

7.5

18.0

different sizes that could be deployed to
serve a VAV system. At 40-percent flow,
the 18-in. (464-mm) fans meet the FEI

fan and 0.82 for the backward-inclined
fan.
Figure 2 shows the FEI-rating bubble

Airflow

3.0

fan is in compliance at 40-percent flow,
it is not at duty points associated with
70-percent flow and 100-percent flow, as
the FEI ratings are less than 1.00.
A fan may have an FEI rating above
1.00 at average flow and an FEI rating

Static pressure

curve for the 18-in. (464-mm) backwardinclined fan. Here, we see that while the

2.5

10

2.0

8

1.5

6

1.25

Fan curve
System curve

100%
%
70%

5.0

1.0

4

0.5

2

40%
0
FEI = 1.00
FEI = 1.10

below 1.00 when speeded up to full flow,
which would be unacceptable from a
regulatory perspective. Selecting a fan
to have an acceptable FEI rating at peak
flow will nearly always ensure the fan

0.0

0

FEI = 1.20

0

3

6

9

0.0

1.5

3.0

4.5

generally increases its FEI rating.
In the case of the 24-in. (622-mm) and

12

6.0

15

7.5

18.0

8.5

21
24
cfm x 1,000
10.5

Airflow

is in compliance when it serves a lesser
load, as slowing a fan's rotational speed

12.0
m3/s

12

in. wg

FEI rating drops to 0.89 for the airfoil

10.5

FIGURE 2. FEI bubble curve for 18-in. (464-mm) backward-inclined
fan showing compliance at low flow rates, but not at the peak
design condition.
kPa

threshold of 1.00, while at full flow, the

8.5

21
24
cfm x 1,000

12.0
m3/s

FIGURE 3. FEI bubble curve for 22-in. (565-mm) backwardinclined fan showing compliance at all three duty points of
interest.

27-in. (686-mm) fans, the FEI ratings for all of the duty

Figure 3 is the FEI bubble chart for the 22-in. (565-mm)

points of interest (40 percent, 70 percent, 100 percent) are

backward-inclined fan. At the 40-percent and 70-percent duty

greater than 1.00. Considerable energy could be saved by

points, the FEI rating is 1.21 and 1.12, respectively. At the

using these larger fans.

100-percent duty point, it is just within compliance at 1.04.

w w w. a m c a .o r g

20 19 A M CA i n m o t i o n

5


http://www.amca.org

AMCA InMotion - September 2019

Table of Contents for the Digital Edition of AMCA InMotion - September 2019

Contents
AMCA InMotion - September 2019 - BB1
AMCA InMotion - September 2019 - BB2
AMCA InMotion - September 2019 - Cover1
AMCA InMotion - September 2019 - Cover2
AMCA InMotion - September 2019 - Contents
AMCA InMotion - September 2019 - 2
AMCA InMotion - September 2019 - 3
AMCA InMotion - September 2019 - 4
AMCA InMotion - September 2019 - 5
AMCA InMotion - September 2019 - 6
AMCA InMotion - September 2019 - 7
AMCA InMotion - September 2019 - 8
AMCA InMotion - September 2019 - 9
AMCA InMotion - September 2019 - 10
AMCA InMotion - September 2019 - 11
AMCA InMotion - September 2019 - 12
AMCA InMotion - September 2019 - 13
AMCA InMotion - September 2019 - 14
AMCA InMotion - September 2019 - 15
AMCA InMotion - September 2019 - 16
AMCA InMotion - September 2019 - 17
AMCA InMotion - September 2019 - 18
AMCA InMotion - September 2019 - 19
AMCA InMotion - September 2019 - 20
AMCA InMotion - September 2019 - 21
AMCA InMotion - September 2019 - 22
AMCA InMotion - September 2019 - 23
AMCA InMotion - September 2019 - 24
AMCA InMotion - September 2019 - 25
AMCA InMotion - September 2019 - 26
AMCA InMotion - September 2019 - 27
AMCA InMotion - September 2019 - 28
AMCA InMotion - September 2019 - 29
AMCA InMotion - September 2019 - 30
AMCA InMotion - September 2019 - 31
AMCA InMotion - September 2019 - 32
AMCA InMotion - September 2019 - 33
AMCA InMotion - September 2019 - 34
AMCA InMotion - September 2019 - 35
AMCA InMotion - September 2019 - 36
AMCA InMotion - September 2019 - 37
AMCA InMotion - September 2019 - 38
AMCA InMotion - September 2019 - 39
AMCA InMotion - September 2019 - 40
AMCA InMotion - September 2019 - 41
AMCA InMotion - September 2019 - 42
AMCA InMotion - September 2019 - 43
AMCA InMotion - September 2019 - 44
AMCA InMotion - September 2019 - Cover3
AMCA InMotion - September 2019 - Cover4
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