Recently my office manager said this, after I requested a desk fan:
…using a fan causes a draught, which then leads the air conditioning to believe it’s cooler than it is and it then blows out even more hot air
I responded saying this is incorrect as fans simply move air, they don't make it cooler. It feels cool to us, but would make no difference to the air temperature measured by the air con.
I thought this would be an interesting question to post here, and would of course give me back-up. (For those interested, I got fed up waiting for a fan so I just bought my own.)
So my question is, is there any reason why the use of desktop fans in my office would make the air conditioning think it was getting cooler?
Best Answer
A fan moves air around. It makes people feel cooler, by causing evaporation of skin moisture (sweat). A fan's motor also gets hotter.
Air moving over a thermostat would have no affect (thermostats don't sweat), but the increase in temperature of the fan's motor, would increase the air temperature slightly, causing the air conditioning to work harder.
If the fan was directed in such a way, that it was moving air from a place with a different temperature, that may also have an affect. For example, a fan directed such that it was aiding warm air move from outside to inside, would increase the inside air temperature, and make the air conditioning work harder.
If you blow a fan over a bucket of water, then it would aid evaporation. Since evaporation is accompanied by cooling, it may help the air temperature cool, which would help the air conditioning work less.