ASHRAE Journal Supplement - AMCA InMotion - September 2019 - 6

Fan total pressure

FEI Training Available
Fan curve

FEI is the subject of two online courses available through
AMCA and Productive Energy Solutions:
■

Surge region

Introduction to Fan Energy Index (FEI) for StandAlone Fans. With special sections for code officials
and energy professionals who design and implement
energy-efficiency programs for electric utilities, this
course describes the concepts behind FEI, advantages of FEI compared with FEG, how to use FEI to
estimate lifetime fan energy savings, and methods
for applying FEI in building codes and efficiency

Airﬂow

programs.
FIGURE 4. Typical fan curve showing surge
region.

■

Calculating Fan Energy Index (FEI) for StandAlone Fans. Designed for anyone seeking detailed
knowledge of the inner workings of FEI, this training

Structural Limitations and Surge

explores the engineering methods used to deter-

A fan needs to be operated within a range of speeds

mine FEI ratings. It is based on ANSI/AMCA Stan-

per the manufacturer's rating. If a fan is operated at a

dard 208-18.

speed too high, it will be vulnerable to its structural
limitations.

The courses are self-guided and immersive, full of
interactive elements. As learners progress through the

First, we will consider problems related to structural

courses, they are given opportunities to accumulate

integrity. Let's say a fan is selected properly for peak ﬂow

points by answering questions and solving problems.

rate. If the manufacturer rated the fan for that duty point,

Introduction to Fan Energy Index (FEI) for Stand-

the impeller should have sufﬁcient structural strength to

Alone Fans is worth 1.5 professional-development

withstand the associated rotational speed and centrifugal

hours (PDH). Calculating Fan Energy Index (FEI) for

forces.

Stand-Alone Fans is worth 3.5 PDH. The cost is $79

In their quest to maximize FEI ratings, system designers
may be tempted to oversize fans, which can lead to surge.

for the former, $199 for the latter, and $249 for both.
To enroll, go to http://bit.ly/FEI_Training.

Operation in the surge region can result in violent pulsations that can damage a fan or cause injury to personnel.
Responsible, experienced HVAC-system designers know
to ensure a sufﬁcient safety margin in a fan's available
peak pressure (sometimes called pressure reserve)-that is,
ensure the duty point falls sufﬁciently to the right of peak
fan pressure so that the fan does not operate in the surge
region (Figure 4). Typically, for both fans and centrifugal
chillers, maximum efﬁciency is achieved with the largest
impeller not in surge, while the "best" selection may be
one size smaller to prevent problems if the system has
higher-than-predicted pressure drop.

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

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

http://www.bit.ly/FEI_Training http://www.amca.org

ASHRAE Journal Supplement - AMCA InMotion - September 2019

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