Ceiling Fan Speed Of Rotation Spinifex Fans

Ceiling Fan Speed Of Rotation Spinifex Fans

How Fast Should A Ceiling Fan Rotate

The speed at which a ceiling fan rotates is a key performance characteristic.  Ideally a fan will offer a good range of speeds of rotation, from slow to gently circulate the air in a room to fast to offer an effective cooling breeze. About 90 revolutions per minute (rpm) to 200rpm is the norm for conventional 130cm diameter ceiling fans in Australia.  While this range of speeds meets most people’s needs, there are a number of good and bad reasons why your fan may operate outside these parameters.

Super slow ceiling fan rotation

Occasionally we are asked for a ceiling fan that rotates very slowly.  Usually this question comes from people who have previously owned an older fan that barely moved the air.  There are two key reasons why a new fan seems so fast to these people.

High speed start: It used to be the case that with some fans you had to start them on high to get them going then you could back off the speed to something more reasonable.  Motor technology has improved and now good ceiling fans use motors with more ‘poles’ and better quality ‘windings’ making starting easier.  With this has come a trend to allow fans to be started from all speeds, limiting how slow the lowest speed can be and still reliably start the fan turning.

Deteriorating controls:   Over time the controls of some fans deteriorate resulting in increased capacitance and a slowing of the motor speed.  Like a frog in hot water, this happens slowly over time and you don’t notice it until someone installs a new fan and it seems awfully fast.

‘Efficient’ ceiling fans and speed of rotation

Slow moving fans use less electricity but they also move less air reducing their cooling benefit.  Some manufacturers have used this as a trick to promote their fans as being more energy efficient.  To judge a ceiling fan’s efficiency look at the volume of air it moves on high per watt of electricity consumed.

Ceiling fan noise

When the tip of a ceiling fan blade rotates quickly it creates noise.  The faster it goes the great the noise.  This is a good reason to use a couple of slower moving fans to cool a larger space than relying on a single fast moving fan.

Using ‘Winter Mode’ to lessen draft

A good solution to a fan that is moving too much air is to use its ‘winter mode’.  This reverses the direction of rotation, which substantially reduce the feeling of draft from the fan.  This is a good tactic for fans in bedrooms where you want very gentle air movement while sleeping.

Ceiling Fan Speed Of Rotation Spinifex Fans

Ceiling fans slowing down over time

As mentioned above, failure of the control capacitors in a ceiling fan can result in it progressively slowing down over time.  It is a fairly uncommon problem and usually results in the fan being replaced.  If you are particularly fond of your ceiling fan you will most likely have to replace one or both of: i) the primary capacity in the fan itself, and ii) the speed control capacitors typically mounted behind the wall speed control.  This work would have to be done by a licensed electrician and would likely void any remaining warranty on the fan.

Impact of voltage variation on ceiling fan speed

A change in local voltage will impact the speed of rotation of your ceiling fan.  A higher voltage will increase the speed and a lower voltage will decrease it.  This often accounts for changes in speed of rotation of approximately +/- 20 revolutions per minute.  For all the tech savvy folks out there, the relationship between speed and voltage is more complicated than simple linear proportionality.

Variable speed steady state controllers

Always check with the installation manual of your ceiling fan before using a steady state speed controller.  Chances are they will be explicitly identified as being incompatible with quality ceiling fans because they produce electrical resonance in the fan resulting in an annoying humming noise.  If it were this simple to have fully variable speed control all manufacturers would do it.

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