Ceiling Fan Blades: 4 or 5?
If you’re in the market for a ceiling fan, you are probably wondering how ceiling fans with four blades compare to those with five. How many blades are most effective at moving the most air most efficiently?
Factors Determining Ceiling Fan Performance
The following factors determine the overall performance and effectiveness of ceiling fans:
- Motor quality, strength and speed
- Pitch of blades and blade irons (blade holders)
- The blades' design and condition
Motor Quality, Strength and Speed
A ceiling fan’s motor speed is measured in RPMs (revolutions per minute). A ceiling fan with greater power is better able to overcome the resistance resulting from fan blades pushing air. Therefore, a fan that is fast and powerful will move more air, revolve faster and provide greater performance than one that is slower and less powerful.
What is Pitch and How Does it Affect Performance?
Pitch is the angle or slant of the ceiling fan blades and the blade irons that connect them to the fan motor. Pitch is measured in degrees and represents the angle between the blade’s slant and true horizontal. A blade that is perfectly horizontal with respect to the floor will move very little air, so proper blade pitch is an important factor in determining the amount of air the fan will move with each revolution.
There is no universally ideal blade pitch, as it differs between various manufacturers and ceiling fan designs. To determine the ideal pitch for you fan, refer to the documentation provided with the fan or contact the manufacturer.
Blade Design and Condition
Various blade designs create different degrees of air resistance and the length, width and finish of the blade all affect the fan’s aerodynamic properties and level of friction as it moves air. Over time, worn blades and blade irons can warp, thus altering the pitch of the blade. This decreases fan effectiveness and may create wobbling and excessive noise.
Sometimes it’s possible to bend blade irons back into alignment, but applying anything more than gentle pressure will likely crack or break the irons. Therefore, you should not attempt to bend any blade irons that are significantly out of alignment. Switching the positions of blades may alleviate minor problems caused by warped blades, but replace those that are severely warped.
How Many Blades Move the Most Air?
When comparing ceiling fans with equally fast and powerful motors, blades in good condition and ideally pitched, a fifth blade will increase the drag on the motor, the price of the fan, and will sometimes generate additional noise. The additional drag decreases the RPM of the blades, reducing the CFM (Cubic Feet per Minute) of air moved. All factors being equal, a 4-bladed fan moves slightly more air than one with 5 blades. Because this difference is slight, select a well made fan with a powerful motor.
Next, consider the “extras” you want, such as lighting, remote control and dual direction capability. Once you’ve narrowed down your selections, choose the fan you find most aesthetically pleasing and that will best enhance the décor of the room in which it will reside.