Last Updated on October 9, 2022 by Barry Gray
I always remember those old 1950s and 60s movies, detective movies, with the stereotypical cynical detective sitting in his cramped overheated office and a lazy fan rotating overhead. The fan never makes a difference, and the characters always seemed to be covered in layers of sweat.
Ceiling fans have no built-in ability to change the temperature in a room, and the only time they are effective is when the moving air they produce comes into contact with human skin. If the ceiling fan is installed in a room with an air conditioner, the ceiling fan will spread the cool air.
Using a ceiling fan in an empty room is a waste of energy and money. Without an air conditioner running, the only impact ceiling fans have on the air temperature in a room is to increase it.
Ceiling Fans Do Not Cool A Room
In a room filled with hot air, the only effect a ceiling fan will have is to move the hot air, which will have no impact on the room’s temperature.
In fact, as counterintuitive as it seems, ceiling fans are a source of heat that the moving air will transfer to the immediate atmosphere in the room.
The fans motor can heat up to between 1300F and 1500F and is the primary source of heat; however, if the fan has a light bulb included in the device when this is turned on, it also generates significant heat. A 60-watt bulb will heat up to 2000F (900C) on the glass surface.
While air conditioners work by removing the heat from the air, fans do not impact the air temperature in a room.
If Fans Don’t Cool The Room, Why Install Them?
Even though fans don’t actively cool the air, they cause the air temperature to be more evenly distributed around the room. If any air pockets in the room have higher (or lower) temperatures, the fan will move these around and so even out the temperature differentials in the room.
If there is a nice warm spot at the window during winter, a fan will help spread the warmth to the rest of the room.
If the air being moved around touches your hot, sweaty skin, evaporation cooling will take place.
It works very much like the inside of a standard household refrigerator in that when the hot air touches your skin, it evaporates the sweat, which in turn removes the latent heat from your skin. An easy example of evaporative cooling is the effect moving air has when you run. As the air touches the skin, it rapidly cools down.
A secondary effect of the air touching the skin is called convection cooling. Once again, this effect only occurs when the moving air touches your skin. However, in this instance, your skin heat is transferred to the moving air.
Ceiling Fans Do Help Air Conditioning
Air conditioners work very differently from fans, whereas, unlike a fan, an air conditioner affects the temperature of a room.
The method of air-conditioners may differ from what most people assume.
Air-conditioners do not cool the air; instead, they extract the heat from the room’s air, transfer it outside, and release the extracted hot air into the atmosphere.
With the heat removed, the air molecules lose energy and heat. The now colder air is returned to the atmosphere in the room.
The method by which compressor-driven air conditioners remove the heat from the room is as follows.
The air conditioner has five essential components which cause the hot air to be removed from the room. The components are:
- Evaporator coil
- Condenser coil
- expansion valve
The air conditioner works by:
- The process starts at the evaporator coil.
- Cold refrigerator gas is pulled through the evaporator coil.
- Simultaneously the air conditioner draws hot air into the unit.
- Physics demands that heat always transfers from warmer to colder objects.
- As the air is hotter than the gas, the heat is transferred to the refrigerant gas through a process called convection.
- With the heat removed, the energy in the air molecules is also reduced, so the temperature lowers.
- The now cool air is pumped back into the room.
- The Air conditioner has to find a way to take the heat out of the now hot refrigerant gas.
- It does this by pumping the heated gas into a compressor and pushing it into the condenser coils.
- As the gas is compressed, its pressure and temperature are raised, making the condenser coils act as heat exchangers, which cause the refrigerant to dissipate its heat.
- As the refrigerant gas cools, it returns to a liquid state.
- The now liquid refrigerant is passed from the condenser coils to an expansion valve, changing the pressure from high to low.
- This change in pressure makes the refrigerant liquid expand and evaporate (causing it to change into a gaseous state).
- As the refrigerant expands, it draws the energy from its surroundings, and the refrigerant gas temperature drops further.
- The now cold gas is again sent into the evaporator coils, continuing the whole cycle.
The real benefit is a fan is when it is installed in a room that is cooled by an air conditioner.
As long as the ceiling fan is installed in a position close enough to the air conditioner, the fan will have the ability to spread the air around the room.
Where To Place The Ceiling Fan
Some folks use the ceiling fan and the air-conditioned as mutually exclusive devices.
It is not the optimum use of either appliance.
The most effective way is to make sure the fan is rotating in a direction that pushes the room’s air down and away from the ceiling.
The best way to check this is to stand beneath the moving fan blades, and if you feel a draft, the fan blades are moving in the right direction.
You should place the fan in a position where it blows air directly into the people in the room.
Turn the air conditioner on, and it will begin to move the air around the room, which evens out the air temperature.
The commonly held belief that ceiling fans function to reduce the air temperature in a room is a fallacy and is untrue. If there is no air conditioner operating, the only way a ceiling fan will be effective is if the moving air comes into contact with exposed human skin.
If an air conditioner is operating, then the ceiling fan has an added purpose in that it assists the fan inside the air conditioner to spread the cool air throughout the room.