Ceiling Fan Performance Guide
We've put together our comprehensive ceiling fan performance guide to help identify the right ceiling fan for your climate, space and preference.
How Fans Cool
Ceiling fans are an excellent low-energy appliance to help keep you cool and comfortable on hot and humid days.
Ceiling fans cool you down by generating a breeze which creates a wind chill effect. This wind chill effect is increased with the increase in wind speed created from the fan, or its “velocity”. The velocity of wind the fan creates is not the same as the amount or volume of air moved. Manufactures of ceiling fans often quote the volume of air a fan produces as a metric, Cubic meters per hour or CM/H.
However while this metric does give you an idea of the fans performance, it does not tell you the full story. For instance, if you are unsure of whether or not you need a 132cm diameter fan or a 152cm diameter fan and you looked to the CM/H of each fan to determine which one would be best for cooling you, you would not be evaluating them correctly. If you make this direct comparison, then it is likely that the 152cm diameter fan will have a higher CM/H number as it displaces more air over a larger area but may likely not create as much wind speed or velocity than the 132cm fan to create the wind chill effect we associate with cooling fans.
Nowdays there are many large fans on the market that show very impressive airflow figures, and while they do move that amount of air, it may be that it does it over a larger area at less velocity. This is why in some cases, depending on the desired outcome, it can be better to have 2 well located fans than 1 large fan for optimal comfort and cooling effect.
ThreeSixty fans have devised a great feature on all of their fans that demonstrates both Volume and Velocity by star rating, this is the FPI – Fan Performance Indicator, so you can be sure you’re getting the right fan for you.
Ceiling & Fan Height
Consider how high your ceiling is and how low your ceiling fan should be positioned for optimal performance.
One often overlooked variable in the performance of a ceiling fan is its distance both from where the air needs to be delivered but also the distance of the fan from the ceiling. While it makes sense that you want the breeze velocity from the fan close to where it is needed to create optimal wind chill and breeze, this air needs to come from somewhere.
Ceiling fans draw in air from above and force it down to create the breeze we feel. If there is a restriction of the available air above the blades for the fan to draw upon, this can create a vacuum effect and begin to draw the same air that is being displaced down, back up to the top of the fan. This results in a “cavitation” effect and impedes the performance of the fan. In most cases the ceiling fan provided to you in a box is not set to its optimum drop away from the ceiling, it is generally provided to you to be 30cm from the ceiling as this is the minimum height requirement on a standard 2.4m ceiling in Australia.
If you have the luxury in your space to be able to drop the fan down from the ceiling via a down rod it is advisable to do so to get the most out of your fans performance. For starters this gets the maximum velocity of the air forced closer to where it is needed, however it is equally important for the fan to have as much unobstructed access to air from above to force it down efficiently.
Ceiling fans also provide indirect cooling through air circulation
A factor to consider with your fans performance is its ability to circulate the air. A fans effectiveness is not only its ability to cool whatever is beneath it, but you will get benefits from the fan circulating air throughout the room. As mentioned in the previous section, if you are able to drop your fan down from the ceiling, you fan will have more air to draw upon to force down.
In an average sized room with an average size fan, the continued forcing of the air down towards the floor will see the air dissipate outwards to the room walls and up until the air has circulated back to the fan, creating a circular flow within the room. This circular flow provides you with the best application of your ceiling fan for full effect. Factors that can affect your fans ability to work to its optimum are if the fan cannot draw enough air from above, if the fan is too close to a wall and the flow is interrupted or if the fan is obstructed by an air conditioning duct and provides uneven amounts of air.
When using fans in a patio or an outdoor situation the circulation of air is affected by the fact that there are no walls present to feed the air back to the fan. So for outdoor applications of ceiling fans the velocity and the CM/H of the fan is most important as the air provided will be forced down and simply be lost in the outdoor environment. Fortunately, when fans are used outdoors it is generally not in a sound sensitive environment so a high velocity, high RPM fan will provide adequate cooling and breeze in these situations.
How to choose a ceiling fan that will provide the best cooling for you
There are many factors that determine the performance of a ceiling fan. With our ever changing tastes in décor and materials available to make them with, ceiling fans are now available in seemingly endless shapes and sizes. Because of these improvements over the years there have been innovations that have influence on the performance of ceiling fans and the sales people that introduce these innovations will point to them as being the most important factor for fan performance, but for the most part, the fundamental factors that influence fan performance remain the same.
The major influencers on a fans performance are the size of the motor, size of blade and shape of the blades, the material the blades are made of, the RPM of the blades of the fan and the pitch of the fan blades. It is the combination of all of these factors working together that will give your fan the best performance results, however, what works the best functionally may not work the best in terms of style and application for the space.
We want our fans to work but also look great, this may be a tricky trade off. For instance, you have a lovely poolside cabana and want a cool breeze provided from a tropical style fan. The fan that would look just terrific in the space has real palm blades and is perfect. Unfortunately, combining the real palm blades with a high degree pitch and powerful motor will only result in damaging the blades and ruining the look and performance of the fan.
A ceiling fans blade pitch is often advised as the most important factor for the fans CM/H performance. A ceiling fans blade pitch is the angle of which the blade sit in order to force the air downwards. While this is no doubt important, pointing to this to be the best indicator is too simplistic. Consider a fan with a small motor and average length blades. If the manufacturer of this fan has put a 25 degree pitch on the blade, which could be considered high, the small motor will have a difficult time getting the blades to push through the resistance of the air it is being tasked to push down, it will be slow ineffective and probably overload the motor.
On the other hand the manufacturer may overcorrect this and put a 5 degree pitch on the blade, in which case the blades will be able to spin around at a great pace as they are actually not at an angle to force any air down, so it may look like it is doing a great job but in fact doing very little for air delivery. The blade pitch argument has been further watered down now with more curved and moulded blades having various pitch angles along the length of the blade.
Another long standing argument on fan performance is how many blades is best 3,4 or 5? The answer, it depends? Just saying 3 blades is better than 4 blades is not going to be correct. We have known single blade fans that work better than some 3,4 and 5 blade fans. Again, it comes back to the fundamentals mentioned earlier.
So how do I consider these fundamentals when choosing a fan? It all comes down to the specification the manufacturer has put into the fan and its design intent. The matching of these variables needs to be decided at design phase for the fan. The ceiling fan should be made with a motor that is adequate to match the size of the blades that are intended to go on it, at a degree pitch that will give the best downward force of air at an RPM that will achieve this result.
You can trust that ThreeSixty has considered these variables with our products. The input you can have in selecting the correct fan and performance for you is to evaluate your needs and check it against what the fan can provide you. What is the right size? Is the CM/H advertised for by the fan adequate for its size? Where is it going to be placed? Is it the right material for the application?
As a rule of thumb for purchasing a fan with performance in mind, knowing now what goes into making a fan perform its best, our advice is to choose the largest fan with the best CM/H and wind velocity, made form a material that is suitable, that will look the best in your selected décor.
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