How many blades are the most efficient for ceiling fans?

The number of blades has little effect on fan efficiency. All the number of blades really affects is the cost: more blades = higher cost.

What matters most is the pitch of the blades. Blade pitch usually ranges from 8-15 degrees... the higher the degree, the more air the fan will circulate at slow speeds.

See http://www.homedepot.com/HDUS/EN_US/energy/en_learn_ceilingfans.html , http://www.hometips.com/cs-protected/guides/ceilingfans/ceilingfan_blades.html , http://www.phillyburbs.com/pb-dyn/news/288-05242006-661097.html

4

Six blades are more efficient that 5, 4 or 3-blade models due to the short space between them. When circulating, you won't feel that "missing link of air" effect between passing blades 3 and 4-blade fans suffer resulting is less airflow.

Motor size, blade pitch AND blade size plays a huge role in efficiency. Don't assume the larger the motor, the better will it perform.

Common things to look for on what I call perfect fans are: 5 blades @ 15-degrees pitch no bigger than 52" with a 188 X 25mm that's a excellent fan.

Another similar case will be a 52" 6-blades with 14-degrees pitch and the same motor size or larger. remember, the extra blade/blade arm weight 2-lbs. that's why these have 1-degree less than a 5-blader of the same size.

A larger than 52" up to 55" with 4-blades can also use efficiently a 188 X 25mm with a 16-degree pitch.

Here's two examples of what are NOT good fans; a 60" (or larger) 5-blades with 13 (or less) degrees pitch and a 188 X 25mm motor or less. A 60"(or larger) fan with a 212 X 25mm and a 18 or higher pitch. they will move, but will not circulate a good amount of air.


These are NOT efficient at all, they both have larger blades with inapropriate motors size and/or pitch.
These combinations are always resulting in less airflow forcing the motors to perform extra hard which eventually will burn out them.

i think around 6 to 8 around that number