[GTO]

Just creating a new thread for a small bit of advice that a BHPian gave me, but boy has it made a difference .

Simple, small trick that is enormously effective = keep the ceiling fan on WITH the air-conditioner. It isn't necessary to keep the ceiling fan on full blast; even a low or medium speed setting will do. But it will significantly reduce the temperature of your room, lend a helping hand to your air-conditioner, keep your energy bills lower and lengthen the life of your air-conditioner (due to less work).

Bombay is currently experiencing one of the hottest Octobers in history. It is too darn hot and that, along with the humidity, makes it extremely draining on your body.

Still, I am sitting cool as a cucumber thanks to the AC, ceiling fan on medium speed and the blinds down. This morning, my 1.5-ton home-office AC was struggling to keep the room cool on 23°C @ blower level 2 / 3. Instead of lowering the temp to 21°C or 22°C and putting the AC on max blower, I put the ceiling fan on level 3. The AC? Currently on 26°C in a H-O-T afternoon, but I am sitting cool as a cucumber.


Pro Tip: Also put the fan on at night. It'll help maintain a constant temperature in the room while you sleep, and move evenly spread the AC coolness. I have a Hitachi AC that cost 50 grand in the office & a Mitsubishi AC that cost 60 grand in the bedroom, yet it's the 1200-rupee ceiling fan that is the "supercharger" of this story. We never, ever run ACs without the ceiling fan, whether we are working, sleeping or Netflix'ing.

This little trick might be obvious to half of you, although I was part of the other half until a BHPian pointed it out.

When properly installed, ceiling fans allow building occupants to turn up their thermostats by about four degrees warmer than the normal setting without sacrificing comfort. The closer a thermostat’s setting is to the outdoor temperature, the less frequently the air conditioner will run. In turn, this saves money by reducing energy consumption.

Source

[GhostGrid]

I've been using this approach for decades; however, I would want to add that if your air conditioning is operating below 22, you shouldn't use the fan since it might allow moisture to seep into the wall.

I don't have any scientific evidence to support that, though, but fewer houses that have used this approach have experienced it.

[Shreyans_Jain]

Have been doing so for years. It’s simple physics, really. Hot air rises and cold air sinks. Not using the fan means you’ll create a cold zone near the floor, while the rest of the room remains warmer. The circulation provided by the fan ensures proper mixing of the air, and provides a much improved and uniform cooling effect. This principle also increases the efficacy of devices humidifiers, room heaters and air purifiers.

Thumb rule: always keep the ceiling fan running at speeds 1 or 2. Fan + AC at 25 provides better cooling than just AC at 21.

[Capri89]

Yes. Doing so for many years.

Not only this. During night I preset the A/c for auto off after 1 hour. With fan on throughout night the room remains cool till 7 am. During day time auto off varies from 1 to 2 hours depending upon ambient temperature.

Saves electricity consumption significantly.

[roy_libran]

Fully agree. All through Delhi NCR summer on my top floor room/office the 1.5 ton inverter AC ran at 27/28 degree setting with fan on at medium speed. Very low electricity bill and fantastic comfort.

[PPS]

I've been using this approach for several months now. It had to do more with the fact that my 0.75 ton Voltas AC takes a lot of time to cool my smallish bedroom! So one fine day my wife insisted to put the fan on as well, so thats how its been since. I prefer the fan on speeds no more than 2 as it tends to make a bit of noise as well.

[Rodie09]

It's a little different for top floor in my experience. Initially the fan blows warmer air due to the warm roof from the day sunlight. So what I do in my bedroom is to run the ac full blast for 10-15 mins till the air inside is cooled down and then turn on the fan to help with circulation for the rest of the night.

[aviator1101]

Originally Posted by GTO

This little trick might be obvious to half of you, although I was part of the other half until a BHPian pointed it out.

Fortunately yes, accidentally though. One night, while we were staying at Faridkot in a house with tin sheet roof on first floor, where the summer heat is almost unbearable and ACs also fail to work at times, we accidentally switched on the ceiling fan and found that cooling by the AC suddenly became more effective in a very short time.

Thereafter, we realised that switching on the ceiling fan at 2 or maybe even 1, increases the cooling effect, ie AC at 25°C gives an actual feel of 22/23°C.

Maybe it's simple physics, but to a non technical layman like me, it's the result which matters, which in this case is comfort and savings. Win win situation for me.

[TorqMaster]

I have always done this way.

While it really does work to cool the room, please do note there is one negative impact. The ac filter of the indoor unit now gets filled with dust and dirt faster. You may need to clean it, say every 3 weeks if you were cleaning it every 2 months earlier. I say it’s an acceptable trade-off.
I found the slowest setting of the ceiling fan is the most comfortable for 26C AC setting .

[PaddleShifter]

Rajasthan heat/ Chandigarh sunmers:

Our AC usage has a fixed pattern everywhere. Run fan at “full speed” and augment it with an AC’s cooling while the AC is set at 27/28 degrees C.

The AC serves the purpose of throwing water (humidity) out of the room and make the air cooler so that fan can do the rest of the job by actively blowing cool air onto the people present in the room.

[Gansan]

I have been doing this for years. Set the Ac just a couple or three degrees below ambient room temperature, run the ceiling fan at a mild speed, and feel cool and comfortable through the night.

It is called the wind chill factor. For example 15 deg C outside temperature will feel comfortable in a normal T shirt during winter, if there is no wind. But let there be a breeze, and we will shiver in the same temperature. The same principle works for the Ac.

[kaps454]

Beg to differ, apartments in the gulf having central ACs never had ceiling fans, not because they could afford not to but because it was counter-productive

A fan keeps you cool, not by cooling the environment, but by increasing the evaporation of sweat (a natural process when the core temperature rises). It actually forces the warmer air from the ceiling towards the floor. An AC does cool down the air within the confined space of the room and increases this natural cool-warm gradient.

So you are actually making the AC work harder and increasing your bills and not actually cooling the area of the room you are in very much. What you are feeling is an expectation bias.

regards kaps454

[NomadSK]

Heat transfer happens through Radiation, Conduction and Convection.

Well, what you have explained with realistic example, is the phenomenon known as "forced convective cooling" (In simpler words, Convection). The heat is transferred from hot object (in this case our body) by the flow of the fluid (air) surrounding the object. Here fan creates the flow of the air. If fan won't be working it will be natural convective cooling. The reason is, as air blows across our bodies it takes away the heat we naturally emit/produce and blows it away from our bodies. That’s why generally when displaying a temperature there’s a term "Feels Like" or "Wind Chill factor" which in general is lower as compared to the actual ambient temperature.

As petrol heads, radiator fan is another example of forced convective cooling, also laptop small fans which helps in lowering the temperature by dissipating the heat.

[sandeepmohan]

Supercharging and whatever else is all well and good.

You need to ensure your room has a proper seal, your aircon is positioned and sized right for the room. If that condensed air is making its way out through gaps and continuous opening and closing of doors, it will result in cooling loss. This is regardless of what type of Air Conditioner you have, fixed or variable speed.

I am in partial agreement to post #12, however the one big difference is that Central Aircon units have a significantly higher throw of air or a higher CFM capability. No compact window or split unit can ever match that level of air flow.

[Rudra Sen]

We’ve been doing this for years.

Our upstairs living room (which is also with an open kitchen) is pretty large with a 25ft/26ft area. Terrace is also right above and in Dehradun summer is very hot and humid.

We coated the terrace surface with heatproof white paint just before the lockdown. The room has a 2.5-ton inverter AC and normally, we keep it running at 22 degrees with two fans (out of four) on at a slow speed.