ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 34

FEI is based on the fundamental characteristics of a
fan-fl ow rate, pressure, and effi ciency-and calculated
for every combination of fl ow rate and pressure. The
basis of FEI, then, is that the point of operation on a fan
curve, not the fan itself, is limited. This is important, as
the location of an operating point on a fan curve impacts
the power consumption of the fan. The result is that
fan-system designers choose fans operating in the most
effi cient region of their performance envelope (Figure 1).
The FEI Bubble
A fan is not a simple appliance that consumes a relatively
fi xed amount of energy when operated. Rather, it
is a pressure-dependent device that delivers a specifi c
fl ow rate and consumes a specifi c amount of power based
on actual system resistance. The fan curve represents a
continuum of fl ow rate and pressure for a given speed.
When speed is extended across the allowable range
of a fan, an allowable zone of compliant performance
points-commonly referred to as an " FEI bubble " -is
generated (Figure 2).
Exclusions
Like California Title 20, the proposed DOE regulation
excludes safety fans and high-temperature fans. The
regulations also are in agreement concerning the exemption
of fans and blowers embedded in the equipment
listed in Paragraph (a)(3) of Code of Federal Regulations
Title 10, Energy; Chapter II, Department of Energy;
Subchapter D, Energy Conservation; Part 431, Energy
Effi ciency Program for Certain Commercial and Industrial
Equipment; Subpart J, Fans and Blowers; Section
431.174, Test Procedure for Fans or Blowers (https://bit
Pressure
Compliant Range of Fan
2.0
.ly/10CFR_431174). Where the regulations signifi cantly
differ is on the matter of embedded fans as defi ned in
ANSI/AMCA Standard 214-21-that is, fans " part of a
manufactured assembly where the assembly includes
functions other than air movement. " This defi nition
describes most industrial-process equipment. California
Title 20 has evolved to exempt embedded fans and blowers
that are available only as part of manufactured assemblies.
The proposed DOE regulation does not allow for
this broader embedded-fan exemption.
Areas of Concern
Considering the diversity and demanding nature of
industrial applications-the venerable resource " Fan
Engineering: An Engineer's Handbook on Fans and Their
Applications " 1 devotes two chapters to commercial
applications but eight to industrial, many of which have
constraints for proper and safe operation and requirements
for durable design that take priority over energy
effi ciency-four aspects of the proposed DOE regulation
should be of particular concern to industrial-processequipment
manufacturers:
■
very high FEI levels
■ the inclusion of embedded fans
■
■
the inclusion of open radial-bladed impellers above 30
in. (76 cm) in diameter and greater than 3-in. (8 cm) wide
the 150-air-hp (110 kW) upper end of the power range
FEI levels. The proposed FEI levels are dramatically
higher than the 1.0 in California Title 20; Title 24
of California's Building Energy Effi ciency Standards
Low Efficiency Fan
Peak Efficiency
Maximum speed
in which FEI ≥ 1.0
at best efficiency
point
FEI 0.9
1.0
FEI 1.0
FEI
FEI 0.7
Airflow
FIGURE 1. FEI requirements will lead to better fan
selections.
34
2024 AMCA inmot ion
Airflow
FIGURE 2. FEI bubble of compliant operating points.
www.amca.org
FEI 0.8
Pressure
Fan Energy Index - FEI
Static Pressure
https://bit.ly/10CFR_431174 https://bit.ly/10CFR_431174 http://www.amca.org
ASHRAE Journal Supplement - AMCA InMotion - November 2024

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