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Friday, April 23, 2010

Question: Does running a ceiling fan at lower speed decrease power usage?

This is not a biology question - more on to Physics - however of scientific interest

A question for which I have been getting conflicting answers on the web: would someone be able to provide a mathematical proof - in terms of calculations?

Most ceiling fans in India have a regulator (two types - a resistance based one and an electronic one) which controls the speed of the fan.  I have all across believed that running a fan at a lower speed takes up more energy as a good amount is wasted in the regulator (resistance-based) in the form of heat.  But some argue otherwise.

Does someone have a mathematical proof for this - either than it saves energy or it does not?  breaking the answer for Resistance based and electronic one too is fine...
TIA...


I did a small experiment a few days back - the power went out and the UPS kicked in.  I switched off all the lights and fans and then switched on 4 fans at low speed.  The 500W capacity UPS showed 50% load when the 4th fan was switched on.  Then I switched off 2 fans and the load dropped back to 25%.  I then gradually increased the speed of the fans. When both the fans were at their top speed, the load kicked back to 50% - which at an initial level goes on to prove that running a fan at lower speed is sure to take lower load and use lower power.  However, I have the small socket type (electronic) regulators at home.  I am not sure if the same holds true for resistance type regulator.  So if someone has started a research on this, please continue.

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