CEILING FAN TEST PROCEDURE DEVELOPMENT TESTING 

FINAL REPORT, PART 1:

ENERGY CONSERVATION PROGRAM FOR CONSUMER 

PRODUCTS: 

Ceiling Fans

October 2014 

U.S. Department of Energy

Assistant Secretary

Office of Energy Efficiency and Renewable Energy

Building Technologies Program 

Appliances and Commercial Equipment Standards 

Washington, DC 20585
This Document was prepared for the Department of Energy

by staff members of

Lawrence Berkeley National Laboratory 

2 
CEILING FAN TEST PROCEDURE DEVELOPMENT TESTING 

FINAL REPORT, PART 1

TABLE OF CONTENTS

1. INTRODUCTION ...............................................................................................................5

1.1. Current Test Procedure ...........................................................................................5

1.2. Products Tested ........................................................................................................7

2. USE OF TEST CYLINDER ................................................................................................8

3. USE OF FALSE CEILING ................................................................................................10

4. ACCURACY OF VELOCITY SENSORS ........................................................................13

5. INTERACTIVE EFFECTS OF MULTIPLE FAN HEADS .............................................15

6. AIRFLOW FROM TILTED FAN HEAD .........................................................................17

7. VERTICAL DISTANCE FROM BLADE TO SENSORS ...............................................19

3 
LIST OF TABLES

Table 1: Products used in ceiling fan test report. .............................................................................7

Table 2: Air velocity variance without a test cylinder as percentage of the variance with a 

test cylinder ..............................................................................................................9

Table 3: Airflow and power measurements for different test configurations of a multihead fan system. .....................................................................................................16

Table 4: Testing results for an adjustable tilt fan head. .................................................................18

Table 5: Testing results for both vertical distance measurements. ................................................20

LIST OF FIGURES 

Figure 1: Side view of testing room in current test procedure. ........................................................6

Figure 2: Top-down view of testing room and placement of sensor axes in current test 

procedure..................................................................................................................6

Figure 3: Airflow without test cylinder as percentage of airflow with test cylinder for 

Fans 1, 2, and 3. .......................................................................................................8

Figure 4: Airflow at all speeds for Fans 4 through 8 with a false ceiling, expressed as a 

percentage of each fan’s airflow without a false ceiling. .......................................11

Figure 5: Airflow for standard and hugger mount of Fan 9 with false ceiling, expressed as 

a proportion of the airflow for standard mount without a false ceiling. ................11

Figure 6: Airflow with a false ceiling as a function of the difference between false ceiling 

size and fan diameter for all speeds of hugger Fans 4 through 8. Airflow is 

expressed as a percentage of each fan’s airflow without a false ceiling. ...............12

Figure 7: Distribution of standard error of air velocity measured at two labs. The dotted 

red line indicates the mean of each distribution.....................................................13

Figure 8: Measured standard deviation of Fan 1 air velocity measurements from Lab 2, 

compared to the standard deviation expected if all of the variation in 

measurements resulted from the accuracy of the sensors alone. ...........................14

Figure 9: Airflow velocity profiles on high speed for multi-head fan system with both 

heads turned on simultaneously, and the sum of testing each fan head 

individually. ...........................................................................................................15

Figure 10: Airflow velocity profile along 4 sensor axes, for an adjustable tilt fan head. 

Tests were conducted with fan head point straight down, and tilted 15° 

away from straight down in the direction of axis C. ..............................................17

Figure 11: Vertical distance test for Fan 2. ....................................................................................19

Figure 12: Vertical distance test for Fan 11. ..................................................................................20

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CEILING FAN TEST PROCEDURE DEVELOPMENT TESTING 

FINAL REPORT, PART 1

1. INTRODUCTION

The U.S. Department of Energy (DOE) conducted a series of tests to assess the impact of 

proposed revisions and additions to the current DOE test procedure for ceiling fans on airflow 

and power consumption measurements. DOE collected and analyzed data on airflow and power 

consumption for the following topics: 

• Impact of using a test cylinder for all ceiling fans

• Impact of using a false ceiling for standard and hugger mount ceiling fans 

• Accuracy requirements of air velocity sensors 

• The interactive effect of multiple fan heads and the impact of estimating airflow and 

power using measurements of individual fan heads 

• The effects of measuring airflow from a tilted fan head

• Impact of measuring the vertical distance from the middle of the blade tip blades to 

sensors or the bottom of the blade tip to sensors 

1.1. CURRENT TEST PROCEDURE

In the current DOE test procedure (10 C.F.R. 430, Subpart B, Appendix U), the ceiling fan is 

mounted above a test cylinder, as illustrated in Figure 1, that has a diameter that is 8 inches wider 

than the ceiling fan blade span. At the bottom of the cylinder, airflow velocity sensors are placed 

from the center of the cylinder directed radially outward at 4-inch intervals to measure the radial 

airflow pattern (see Figure 2). Measurements of airflow velocity in units of feet per minute are 

taken by sensors along each axis and averaged. The total airflow in units of cubic feet per minute 

(CFM) is calculated as the average air velocity multiplied by the area (in cubic feet) covered by 

the airflow sensors. The recommended dimensions for the testing chamber are 20 ft. x 20 ft. with 

an 11 ft. high ceiling. This test procedure is based on the ENERGY STAR Version 1.1 test 

procedure for ceiling fans. The current test procedure does not specify a methodology for 

measuring airflow for hugger mount ceiling fans, tilted fan heads that cannot be pointed directly 

down, or multi-head fan systems. It also does not specify a procedure for measuring standby or 

off mode energy consumption. 

5 
Figure 1: Side view of testing room in current test procedure.

Figure 2: Top-down view of testing room and placement of sensor axes in current test 

procedure. 

6 
1.2. PRODUCTS TESTED

Table 1 shows the list of the 11 products along with relevant attributes used in this analysis. 

Table 1: Products used in ceiling fan test report.

Fan 

ID

Blade Span 

(inches)

Number of 

Speeds

Standard 

Mount 

Hugger 

Mount 

Multi-Head 

Fan

Notes

1 44 3 X

2 52 3 X

3 56 3 X

4 44 6 X

5 44 3 X

6 44 4 X

7 52 3 X

8 52 6 X

9 52 3 X X Multi-mount fan

10 24 3 X Two 24" fan heads

11 52 3 X Curved fan blades

7 
2. USE OF TEST CYLINDER

To determine the effect of the test cylinder, DOE tested Fans 1, 2, and 3 both with and without 

test cylinders. DOE compared the airflow without the test cylinder to airflow with the test 

cylinder. Figure 3 shows the airflow without a test cylinder, expressed as a percentage of the 

airflow with a test cylinder, for all speeds of the three fans. Airflow without a cylinder ranged 

from 3% lower to 11% higher than the airflow with a cylinder. On average, the airflow without 

the cylinder was 5% higher than airflow with the cylinder. 

Figure 3: Airflow without test cylinder as percentage of airflow with test cylinder for Fans 1, 2, and 3.

DOE also investigated the variability of the air velocity measurements used to calculate airflow.

In the test procedure, 100 air velocity measurements are taken, once per second, at each sensor 

position and axis. These measurements are then averaged to get a mean air velocity at that 

position and axis. DOE used the variance of the 100 air velocity measurements at each sensor 

position and axis as a measure of the variability of the air velocity measurements. Table 2 shows 

the mean variance of the air velocity measurements for each fan without a test cylinder, 

expressed as a percentage of the variance with a test cylinder. On average, variance without a 

cylinder was 20% lower than variance with a cylinder.

8 
Table 2: Air velocity variance without a test cylinder as percentage of the variance with a test cylinder

Fan Mean air velocity variance without a test cylinder as a 

percentage of the variance with a test cylinder

Fan 1 66.5%

Fan 2 87.2%

Fan 3 85.9%

9 
3. USE OF FALSE CEILING

DOE tested hugger (aka low profile) ceiling fans and standard mount fans to investigate the use 

of a false ceiling. In the current test procedure, as shown in Figure 1, there are over 40 inches of 

clearance between the ceiling of the testing room and the fan blades. A false ceiling is a board or 

other flat surface, suspended from the ceiling of the testing room, to which test fans are mounted. 

Once mounted to a false ceiling, the clearance between the fan blades and the false ceiling is the 

same clearance that the blades would have after installation in a home, typically 15 inches or 

less. 

To determine the effect of a false ceiling on hugger fan airflow, DOE tested Fans 4 through 8 

with and without a false ceiling. (Fan 9 was not tested in the hugger configuration without a false 

ceiling.) Two different false ceiling sizes, 60 and 68 inches square, were used in the tests. These 

false ceilings are between 8-24 inches larger than the ceiling fans tested, depending on the size of 

the fans. Figure 4 shows airflow for all speeds of each fan with a false ceiling, expressed as a 

percentage of airflow without a false ceiling. On average, airflow with a false ceiling was 37% 

lower than the airflow without a false ceiling. 

 

10 
Figure 4: Airflow at all speeds for Fans 4 through 8 with a false ceiling, expressed as a percentage of each 

fan’s airflow without a false ceiling. 

To determine the effect of a false ceiling on the airflow of multi-mount fans that can be mounted 

in standard and hugger configuration, DOE tested the multi-mount Fan 9 in three configurations: 

1) standard mount without a false ceiling 

2) standard mount with a false ceiling 

3) hugger mount with a false ceiling. 

Figure 5 shows airflow at all 3 speeds for the two configurations with a false ceiling, expressed 

as a percentage of airflow for standard mount without a false ceiling. On average, and compared 

to the standard mount without a false ceiling, the airflow in the standard mount configuration 

was 30% lower with a false ceiling, and airflow in the hugger mount configuration was 46% 

lower with a false ceiling. DOE assumed that the airflow of the hugger mount without a false 

ceiling would be nearly identical to the airflow of the standard mount without a false ceiling, 

because the current test procedure requires that the fan blades are in the same position relative to 

the testing room ceiling and test cylinder for both mounting options. 

Figure 5: Airflow for standard and hugger mount of Fan 9 with false ceiling, expressed as a proportion of the

airflow for standard mount without a false ceiling. 

11 
To determine the effect of the size of the false ceiling on hugger fan airflow, DOE used two sizes 

of false ceiling in its tests—60 inches square and 68 inches square. Figure 6 shows the 

relationship between airflow and the difference in size between the fan and false ceiling for Fans 

4 through 8, using the same results shown in Figure 4. Note that tests at all available speeds are 

shown for all fans. There is no clear relationship between airflow and the difference in size 

between the fan and false ceiling in this sample. In addition, DOE tested Fan 5 with both ceiling

sizes, and the mean airflow differed by 3% between the two false ceilings. These results can be 

seen in Figure 4. 

Figure 6: Airflow with a false ceiling as a function of the difference between false ceiling size and fan diameter

for all speeds of hugger Fans 4 through 8. Airflow is expressed as a percentage of each fan’s airflow without a 

false ceiling. 

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4. ACCURACY OF VELOCITY SENSORS

To determine whether sensor accuracy affects ceiling fan airflow measurements, DOE used data 

from Fan 1. DOE first compared the standard error of air velocity measurements from tests of 

Fan 1 at two test labs. Lab 1 used sensors with accuracy equal to the maximum of 5% of the 

reading or 1% of the full range of the sensor. Lab 2 used sensors with accuracy equal to the 

maximum of 2% of the reading or 0.5% of the selected range of the sensor. Figure 7 shows that 

the distribution of standard errors from Lab 1 had a similar range to the distribution from Lab 2, 

and the mean standard errors differed by approximately 5 feet per minute. 

Figure 7: Distribution of standard error of air velocity measured at two labs. The dotted red line indicates the 

mean of each distribution.

13 
DOE also investigated the variability of the individual air velocity measurements from Lab 2’s 

test of Fan 1. DOE used the assumption that the reported accuracy of the sensors provided an 

estimate of a 95% confidence interval for the individual sensor readings. Based on this 

assumption, DOE calculated the standard deviation of sensor readings that would be expected if 

all of the variation in measurements resulted from the accuracy of the sensors alone. Figure 8

shows the ratio of the actual measured standard deviation to the standard deviation expected 

from the sensor accuracy alone. The ratio ranges from 3 to 34, with a mean of 15. 

Figure 8: Measured standard deviation of Fan 1 air velocity measurements from Lab 2, compared to the 

standard deviation expected if all of the variation in measurements resulted from the accuracy of the sensors 

alone. 

14 
5. INTERACTIVE EFFECTS OF MULTIPLE FAN HEADS 

DOE conducted tests to measure the interactive effects of a multi-head fan system. Fan 10 is a 

multi-head fan with two 24” fan heads connected by a rod with a center housing that allows for 

each fan head to be turned on/off individually. 

Fan 10 was first tested with the midpoint of the fan system centered at the origin of the four 

sensor axes. The fan heads were oriented along the A-C sensor axis with the fan heads operating 

simultaneously. In the next test, the fan system was held in the same position and measurements 

were taken for each individual head. In instances where only one fan head was being operated, 

the other fan head was turned off using a switch located on the center housing. 

Figure 9 compares the airflow velocity profile on high speed for both heads turned on 

simultaneously to the sum of testing each fan head individually. The top panel displays the 

velocity profile along the A-C axis and the bottom panel along the B-D axis. The tests with 

individual fan heads produce more airflow along the outermost sensors on the A-C axis. With 

both fan heads operating simultaneously, air is drawn into the center of system, which is also 

apparent along the B-D axis. 

Figure 9: Airflow velocity profiles on high speed for multi-head fan system with both heads turned 

on simultaneously, and the sum of testing each fan head individually.

15 
Table 3 shows the airflow and power measurements for the different test configurations. 

Compared to the airflow when both fan heads are operating simultaneously, the sum of airflow 

measurements from the individual fan head tests is 9% higher on low, 7% higher on medium, 

and 20% higher on high. These results suggest that interactive effects of multiple fan heads act to 

reduce the total measured airflow.

Measurements of power consumption found that tests involving only one operating fan head 

produced power values that were approximately 75% of the power consumption of both fan 

heads operating. As shown in Table 3, summing the power consumption of individual fan heads 

significantly overestimates the power consumption of the fan system with both fan heads 

operational by 50% on low, 42% on medium, and 26% on high speed. 

Table 3: Airflow and power measurements for different test configurations of a multi-head fan system.

Test 

Configuration 

Low Medium High

CFM Power 

(W)

CFM Power 

(W)

CFM Power 

(W)

Fan Head 1 only 1120.28 14.9 1587.05 25.8 2827.01 49.2

Fan Head 2 only 1004.71 14.9 1650.85 26.0 2682.79 46.4

Fan Head 1 + 

Fan Head 2 2124.99 29.8 3237.90 51.8 5509.80 95.5 

Both Heads 

Simultaneously 1957.01 19.9 3012.85 36.3 4607.54 75.7 

Percent 

Difference* +9% +50% +7% +42% +20% +26%

* Sum of individual fan head measurements compared to both fan heads operating simultaneously.

16 
6. AIRFLOW FROM TILTED FAN HEAD

DOE conducted tests on a tilt-adjustable fan head to measure the impact on airflow when the fan 

is directed at an angle other than straight down in the direction of the sensors. For these tests an 

individual fan head from Fan 10 was mounted directly above the center of the sensor axes (i.e., 

above sensor 1). In the first test, airflow was measured with the fan head pointed directly down 

towards the plane of the sensors. Next, the fan head was tilted 15° away from straight down in 

the direction of axis C. 

Figure 10 shows the airflow velocity profile for both test configurations. The top panel shows the 

velocity profile along the A-C axis and the bottom panel shows the velocity profile along the BD axis. The overall shapes of the velocity profiles along the A-C axis are similar with the 

exception that the profile for the tilted fan head is shifted approximately 2 sensor positions along 

the C axis. Along the B-D axis, the sensors measure less airflow from the titled configuration 

compared to the straight down configuration. This is not unexpected since the peak of the airflow 

for the tilted configuration is offset along the C axis.

Figure 10: Airflow velocity profile along 4 sensor axes, for an adjustable tilt fan head. Tests were 

conducted with fan head point straight down, and tilted 15° away from straight down in the direction 

of axis C.

17 
Table 4 shows the total measured CFM averaged over the four sensor axes and summed over 

sensor positions. Measurements for the tilted configuration are systematically lower compared to 

the straight down configuration. In comparison to the straight down configuration, measurements 

for CFM in the titled configuration are 9% lower on low speed, 17% lower on medium speed, 

and 6% lower on high speed. 

Table 4: Testing results for an adjustable tilt fan head.

Configuration CFM Low CFM Med CFM High

Straight Down 1149.50 1891.02 3093.20

Tilted 15° 1041.36 1560.61 2904.22

Percent 

Difference*

-9% -17% -6%

* Tilted configuration compared to straight down.

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7. VERTICAL DISTANCE FROM BLADE TO SENSORS

Fan 2 and 11 were tested to assess the impact of measuring airflow using a vertical distance 

measured from the sensors to the bottom of the blade tip compared to a vertical distance 

measured from the sensors to the middle of the blade tip. Measurements were recorded on low, 

medium, and high speeds for both vertical distance configurations. 

Figure 11 and Figure 12 illustrate the air velocity as a function of sensor position for Fan 2 and 

Fan 11, respectively. The values for airflow velocity are averaged over the four sensor axes. 

Results for high speed are in blue, medium speed in green, and low speed in red. Solid lines 

represent tests where the vertical distance is measured from the sensors to the middle of the 

blade. Dashed lines represent tests where distance is measured from the sensor to the bottom of 

the blade.

Table 5 provides the testing results for the two vertical distance configurations. Shown are the 

measured CFM results on low, medium, and high speed for the two fans averaged over all sensor 

axes and summed over sensor position. Measurements on high and low speeds are consistent to 

within 3% (with respect to the test where distance is measured to the middle of the blade), while 

low speed is within 6%. 

Figure 11: Vertical distance test for Fan 2. 

19 
Figure 12: Vertical distance test for Fan 11. 

Table 5: Testing results for both vertical distance measurements.

Fan ID Vertical Distance 

Measured from

CFM Low CFM Medium CFM High

2 Middle of Blade 1882.21 3199.15 4407.43

Bottom of Blade 1768.73 3105.79 4313.46

11 Middle of Blade 1255.53 2078.14 3339.00

Bottom of Blade 1260.80 2023.25 3321.05

20