This entry was posted on Sunday, September 21st, 2008 at 3:19 pm and is filed under Ceiling, Indoor Lighting, Lighting. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
A ceiling light is very practical, but even more so is one with a fan. There are several factors which determine a fan’s efficacy and efficiency. Each of these factors can be used as a basis for comparison when deciding between different candidate fans to purchase.
A fan’s efficacy (in other words, its ability to generate airflow) is measured by its CFM (Cubic Feet of air moved per Minute) rating. The following factors all have an effect on a fan’s CFM rating:
Length of the fan’s blades. The longer a fan’s blades are, the larger percentage of a room’s air volume upon which the fan will have a relevant impact. This factor is of greater importance in large rooms. The majority of ceiling fans come in one of three sizes (sweep diameter): 36″, 42″, or 52″.
Total surface area of the fan’s blades. The greater a blade’s surface area, the more air it is able to move. However, there can be “too much” surface area (refer to Blade surface area to air-feed ratio below).
Pitch of the fan’s blades. The angle at which the fan’s blades are tilted relative to the X-axis is referred to as the “blade pitch”. The steeper (greater) the pitch, the greater the airflow. Since increased pitch also means increased drag, only fans with well-made motors can support steep pitches. Cheaply-made fans typically have a pitch between 9 and 13 degrees. A pitch of 15 degrees and upwards is considered very good, with numbers in the 20s being the highest.
Speed of rotation. The speed at which a fan rotates, measured in RPM (Revolutions Per Minute), directly correlates to the amount of air moved. Faster rotation equals greater airflow.
Blade surface area to air-feed ratio. In general, more blade surface area means greater airflow. However, if there is too much blade surface area, there will not be adequate space between the blades for air to be drawn through. Fans which have an unusually large blade surface area, such as fans with decorative palm-leaf-style blades or many fans with six blades, do not have adequate space between the blades for an unrestricted amount of air to be drawn through. This results in reduced airflow. The effect of this ranges from negligible to dramatic, depending on the exact dimensions involved. Contrary to popular belief, more blades typically does not equal more airflow. Most four-bladed fans move more air than comparable five-bladed fans spinning at the same speed; this is indeed noticeable on five-bladed fans which have an option to install only four of the blades. Also due to this effect, the overwhelmingly vast majority of industrial fans have three blades.
Height of the fan relative to the ceiling. If a fan is too close to the ceiling, the airflow is restricted; that is, the fan will not be able to draw as much air through its blades as it has the potential to do. For this reason, “hugger”-style fans (those which mount directly to the ceiling without the use of a downrod) are all inherently disadvantaged. The distance that a fan should be mounted from the ceiling is directly correlated with its air-moving potential; no fan should be mounted with its blades closer than 24 inches to the ceiling, however that figure is often far greater with industrial fans. Unfortunately, this is often impossible in household situations due to the fact that a minimum ceiling height of nine feet would be required to meet safety codes (”blades must be mounted a minimum of seven feet from the floor”) and 8 or more feet is typically desired). Excerpt from wikipedia.
September 23rd, 2008 at 8:25 pm
Ceiling light | About Lighting Blog…
Redecorating your home is easy after you have seen this great site that I recommend. You will enjoy inside browsing and shopping for unique lighting fixtures that will light up your home and make it look best the way you want it….
September 23rd, 2008 at 8:26 pm
Ceiling light | About Lighting Blog…
Redecorating your home is easy after you have seen this great site that I recommend. You will enjoy inside browsing and shopping for unique lighting fixtures that will light up your home and make it look best the way you want it….
September 23rd, 2008 at 8:27 pm
Ceiling light | About Lighting Blog…
Redecorating your home is easy after you have seen this great site that I recommend. You will enjoy inside browsing and shopping for unique lighting fixtures that will light up your home and make it look best the way you want it….
September 23rd, 2008 at 8:27 pm
Ceiling light | About Lighting Blog…
Redecorating your home is easy after you have seen this great site that I recommend. You will enjoy inside browsing and shopping for unique lighting fixtures that will light up your home and make it look best the way you want it….