ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 28

formula. By rearranging terms in that formula, we can
fi nd any fan's energy consumption at a particular speed.
We are going to take a quick detour into the mathematics
and equations required to get to that formula.
Readers interested in only the practical application may
choose to skip to the end of this section.
Note: Many of the following equations are from ANSI/
A 24-ft (7.3 m) gear-driven ceiling fan circulates air
inside the Commemorative Air Force Dixie Wing
hangar located on the grounds of Atlanta Regional
Airport's Falcon Field in Peachtree City, Ga.
occur is dependent on the motor/gearbox model as well as
installation and operating conditions. However rare they
may be, these failures simply do not occur with directdrive
motors because there is no gearbox at risk of failing.
Energy effi ciency. In 2021, the U.S. Department of
Energy (DOE) published a fi nal rule changing the regulatory
metric for LDCF from cubic feet per minute per watt
(cfm/W) to ceiling-fan energy index (CFEI). CFEI compares
the performance of a LDCF to that of a theoretical reference
fan. Manufacturers are required by the DOE to report
CFEI at 100-percent speed (CFEI100) and 40-percent speed
(CFEI40). The higher a fan's CFEI, the better the fan will
perform and the more energy-effi cient it is. Note that CFEI
ratings cannot be compared meaningfully across diameters.
A CFEI100 of 1.18 for a 24-ft fan is not necessarily
" worse " than a CFEI100 of 1.20 for a 20-ft fan. One must stay
within a single fan diameter to compare CFEI ratings. See
the AMCA white paper " Introducing Ceiling Fan Energy
Index (CFEI) and Changes to the U.S. Regulation for LargeDiameter
Ceiling Fans " (https://bit.ly/Introducing_CFEI)
for a more detailed explanation of CFEI.
Calculating Energy Consumption/Cost
Calculating CFEI involves comparing the electrical
input power of a fan as measured in a laboratory to the
electrical input power of a reference fan. The energy
consumption of the reference fan is calculated with a
28
2024 AMCA inmot ion
AMCA Standard 208-18, Calculation of the Fan Energy
Index (available to download free of charge at https://bit
.ly/AMCA_208-18). Calculations are performed in inchpound
(I-P) units (cubic feet per minute for airfl ow, feet
for fan diameter, and watts for energy).
We will start with Equation 5.2 for reference-fan
electrical input power (FEPref) from ANSI/AMCA Standard
208-18:
FEPref =
Hi,ref
ηtrans,ref × ηmtr,ref
where:
Hi,ref = fan shaft power, reference
ηtrans,ref = transmission effi ciency, reference
ηmtr,ref = motor effi ciency, reference
To get a value for reference-fan electrical input power,
we need to introduce additional terms and equations and
eventually rewrite the equation for reference-fan electrical
input power in terms of only fan airfl ow and fan
diameter. To do that, we use Equation 5.3 for referencefan
shaft power from ANSI/AMCA Standard 208-18:
(Qi + Q0)
Hi,ref =
(Pt + P0 + ρstd
ρ
6,343 × η0
where:
Qi = fan airfl ow at duty point i
Q0 = airfl ow constant
Pt = fan total pressure
P0 = pressure constant
ρ = fan air density
ρstd = standard air density
η0 = fan-effi ciency constant
To calculate CFEI, the FEI equations found in ANSI/
AMCA Standard 208-18 are used with the following
coeffi cients substituted:
■
Q0 = 26,500 cfm (12.507 m3/s)
■ P0 = 0.0027 in. wg (0.6719 Pa)
■ η0 = 42 percent
www.amca.org
)
Eq. 5.3
× 745.7
Eq. 5.2
https://bit.ly/AMCA_208-18 https://bit.ly/AMCA_208-18 https://bit.ly/Introducing_CFEI http://www.amca.org

ASHRAE Journal Supplement - AMCA InMotion - November 2024

Table of Contents for the Digital Edition of ASHRAE Journal Supplement - AMCA InMotion - November 2024

Contents
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - CT1
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - CT2
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - Cover1
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - Cover2
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - Contents
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 2
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 3
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 4
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 5
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 6
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 7
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 8
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 9
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 10
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 11
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 12
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 13
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 14
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 15
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 16
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 17
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 18
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 19
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 20
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 21
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 22
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 23
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 24
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 25
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 26
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 27
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 28
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 29
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 30
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 31
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 32
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 33
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 34
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 35
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - 36
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - Cover3
ASHRAE Journal Supplement - AMCA InMotion - November 2024 - Cover4
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