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Maximum Ceiling Fan RPMs

Published by: Greg Tillotson
Webmaster for Hansen Wholesale
2/21/2011

Ever wonder why ceiling fans only go so fast? Ever think that if manufacturers just made ceiling fans spin faster, they would move more air? Well, maybe you don't think of these kinds of things, but as the webmaster for the Largest Ceiling Fan Website online, I can't help but have such thoughts.

The fact is: There are UL standards that place limitations on ceiling fan manufacturers that prevent them making fans that spin too fast. These limitations for safety purposes and are meant to minimize the risk of injury should a person raise their hands (or any other object) into the path of the ceiling fan blades while the fan is in operation. Imagine if some ceiling fan blades moved as fast as an airplane propeller and had blades like a machete! Well, UL standards prevent manufacturers from making such products...but they also present challenges to engineers who attempt design ceiling fans for maximum airflow and efficiency.

Maximum RPMS Allowed for Ceiling Fans

The first basic limitation is that no residential ceiling fans are allowed to be installed such that the blades are less than 7 feet from the floor. The second basic limitation has to do with the RPMs at which a fan can spin relative to the thickness of the blades. The concept is that thinner blades can cause more damage of laceration, so they are not allowed to spin as fast as those with thicker blades.

The RPMs allowed for any residential ceiling fan that can be installed on a ceiling less than 10 feet high are restricted by UL based on the blade span and thickness of the blades (see chart below). Any blade less than 3/16" thick cannot exceed the RPMs for 1/8" thick blades. Any blades 3/16" thick or greater cannot exceed the RPMs for 3/16" thick blades. In no case can the fan blades be less than 1/8" thick. No ceiling fan is allowed to be installed with the blades closer than 7 feet from the floor. These limitations are in place to minimize the risk of injury should a person raise their hands (or any other object) into the path of the fan blades while the fan is in operation.

How do RPMs affect airflow?

The amount of air that a ceiling fan produces is certainly affected by how fast is spins. Yet RPMs alone do not produce airflow. The aerodynamics of the blades is every bit as important as the RPMs. If a fan has blades that are straight and flat, it doesn't matter how fast it spins, it's not going to generate much airflow. Take the same blades and give them a 15 degree pitch and the fan will move air, but the RPMs will be slower since the angled blades are now having to perform some work, which puts drag on the motor. You can equate this to the difficulty of rowing a boat when you place the oars flat in the water compared to turning them at an angle. Flat is easy to row, but will not get you anywhere. Angling the blades just a few degrees makes it more difficult to row the boat, but you actually start moving. So imagine the difference in airflow between 2 fans that operate at the same RPM yet one has flat blades and the other has angled blades. The fan with angled blades must have a more powerful motor in order to maintain the same RPM as the fan with flat blades. So judging the airflow performance of a fan strictly by comparing RPMs is of little value. What you really need to know is how much airflow the fan will produce when operating at a particular RPM.

Maximum RPMS Reference Chart

The data below is based on ceiling fans that have a reverse function. Non-reversing ceiling fans are allowed to have slightly higher RPMs. UL actually states the limitations based on the maximum allowed speed of the tip of the fan blade at 3200 feet/minute for 3/16" thick blades and 2400 feet/minute for 1/8" thick blades. We have provided the following data by creating a formula that does this calculation based on the overall bladespan of any particular ceiling fan ranging from 24" to 84".

Based on UL 507 Standards (link to PDF removed by request of UL - 5/30/2013)

Ceiling Fan Maximum RPM Calculator
Blade Span Calculate Max RPM (1/8" Thick Blades) Max RPM (3/16" Thick Blades)
0
0
(Instructions/Details)
Ceiling Fan Maximum RPM Table
Blade Maximum RPM
Span3/16" Thick1/8" Thick
24 509 382
25 489 367
26 470 353
27 453 340
28 437 327
29 421 316
30 407 306
31 394 296
32 382 286
33 370 278
34 360 270
35 349 262
36 340 255
37 330 248
38 322 241
39 313 235
40 306 229
41 298 224
42 291 218
43 284 213
44 278 208
45 272 204
46 266 199
47 260 195
48 255 191
49 249 187
50 244 183
51 240 180
52 235 176
53 231 173
54 226 170
55 222 167
56 218 164
57 214 161
58 211 158
59 207 155
60 204 153
61 200 150
62 197 148
63 194 146
64 191 143
65 188 141
66 185 139
67 182 137
68 180 135
69 177 133
70 175 131
71 172 129
72 170 127
73 167 126
74 165 124
75 163 122
76 161 121
77 159 119
78 157 118
79 155 116
80 153 115
81 151 113
82 149 112
83 147 110
84 146 109

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