ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 14

Because of the relationship between power and
airfl ow defi ned in the fan laws, cfm/W can be gamed
more easily than can CFEI. Figure 2 shows airfl ow vs.
power for fi ve different 24-ft- (7.3 m) diameter fans.
For a given airfl ow, the lower a curve on the chart, the
more effi cient (less power) the fan. Despite differences
in true operating effi ciency at any common duty point,
each of the fi ve fans has a rating of 234 cfm/W (0.110
[m3/s]/W). In contrast, CFEI ratings at high speed are
dramatically different. The most effi cient fan (lowest
power for a given airfl ow) is Fan 1, which has a CFEI
Parameter
Effective date Jan. 19, 2017
Referenced test
standard
Rating
calculation
standard
10 CFR Part 430, Appendix U
cfm/W
May 27, 2021
10 CFR Part 430, Appendix U (corrected*)
10 CFR Part 430, Subpart B, Appendix U
Test speeds
Standby power
Mathematical
function
Compliance
shortcuts
20 percent, 40 percent, 60 percent,
80 percent, 100 percent weighted by
operating hours at speed
Included in calculation based on 12 hr of
standby per day
Linear
Easy. Slowing an ineffi cient fan can make the
fan compliant.
ANSI/AMCA Standard 208, Calculation of the Fan
Energy Index, with the following modifi cations:
(1) use of an airfl ow constant (Q0) of 26,500 cfm,
(2) use of a pressure constant (P0) of 0.0027 in. w.g.,
and (3) use of a fan-effi ciency constant (η0) of
42 percent
100 percent and 40 percent, or the speed closest to,
but not less than, 40 percent
Not included in calculation
Polynomial
Diffi cult. CFEI ratings are more uniform across airfl ow
ranges.
Allows evolution to greater utility (higher airfl ow for a
given fan diameter) at conservative power.
Benefi ts
Familiar
Only two test speeds needed for regulation.
LDCF requirements can be tightened without the
baseline changing.
High-airfl ow (for a given diameter) fans have
diffi culty complying, which impedes their
evolution.
Penalties
Conversely, low-airfl ow fans can be paired
with ineffi cient motors, drives, etc. and still
easily comply, which enables low-effi ciency
models to remain in the market.
Does not adequately address " outlier " very
low-fl ow products, resulting in exceedingly
high ratings.
Makes rebates and green codes diffi cult.
*An erratum to ANSI/AMCA Standard 230-15 was published on May 6, 2021.
14
TABLE 1. Comparison of cfm/W and CFEI.
2021 AMCA inmot ion
Coeffi cients for LDCF were developed to supplement
ANSI/AMCA Standard 208, which was not designed
to handle LDCF.
Coeffi cients were developed using high-volume,
low-speed fans. LDCF class includes " outlier "
very low-fl ow (for a given diameter) products that
subsequently entered the market.
Not well-known; market awareness and education
needed.
rating of 1.72. The least effi cient fan (highest power
for a given airfl ow) is Fan 5, which has a CFEI rating of
0.63. While both Fan 1 and Fan 5 would comply with
the cfm/W minimum-effi ciency requirement, Fan 1
would signifi cantly exceed the DOE minimum-effi ciency
requirement of 1.00 at high speed, while Fan 5 would
be non-compliant, as its CFEI is less than 1.00. Table
2 summarizes the CFEI and cfm/W ratings for each of
the fans in Figure 2. As illustrated by this example,
CFEI provides a better representation of how effi ciently
a LDCF performs.
CFEI
www.amca.org
http://www.amca.org

ASHRAE Journal Supplement - AMCA InMotion - November 2021

Table of Contents for the Digital Edition of ASHRAE Journal Supplement - AMCA InMotion - November 2021

Contents
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - BB1
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - BB2
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - Cover1
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - Cover2
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - Contents
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 2
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 3
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 4
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 5
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 6
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 7
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 8
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 9
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 10
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 11
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 12
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 13
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 14
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 15
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 16
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 17
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 18
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 19
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 20
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 21
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 22
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 23
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 24
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 25
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 26
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 27
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 28
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 29
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 30
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 31
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 32
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 33
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 34
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 35
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 36
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 37
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 38
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 39
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 40
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 41
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 42
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 43
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - 44
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - Cover3
ASHRAE Journal Supplement - AMCA InMotion - November 2021 - Cover4
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