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Does a ceiling fan cool a room?

08/09/2007 8:13 PM

If all the doors and windows are shut and there is no HVAC and you run a ceiling fan will the room temperature rise or fall? Is it wise to run a fan if no one is home?

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#1

Re: Does a ceiling fan cool a room?

08/09/2007 9:19 PM

a fun cannt reduce temperature at any time and anywhere only but rise it. if you feel cool, becaaue it flow air to carry heat from body. if the wether si hot, you need it to feel comfortable. in spite of rising temperature.

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#3
In reply to #1

Re: Does a ceiling fan cool a room?

08/10/2007 2:24 AM

The ceiling fan does not cool room. But it can make air of a room can be more clear if you used a ventilation ceiling or wall fan. Beacause it flow hot air in room to outside.

In this condition it can be turned on when there is not somebody in room, and after that you feel more comfortable when come back the room.

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#5
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Re: Does a ceiling fan cool a room?

08/10/2007 7:36 AM

Beacause it flow hot air in room to outside..

This would only work if you use an air "extractor" a fan only produces a vertical flow of air

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#2

Re: Does a ceiling fan cool a room?

08/09/2007 9:25 PM

The motion of air a fan produces dos not introduce any change in temperature... its just moving air!

Now, if (let's say) the floor or a wall facing certain direction is cooler than the rest of the structure, moving air will simply establish a temp balance within this room.

What air in motion does on living beings is to move the hot air layers (generated by metabolic processes) that surround this being.

Putting these layers into motion facilitates heat exchange and perspiration.

Perspiration is what produces the cooling effect.

On the other hand, there is also an issue related to air humidity and effectiveness of fans... but I'll let someone else to explain this

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#37
In reply to #2

Re: Does a ceiling fan cool a room?

08/11/2007 9:41 PM

Perspiration with subsequent evaporation of the sweat with result in cooling of the surface of the perspirer, but only until the moisture content of the air reaches saturation (100% relative humidity at the air temperature). After that no further evaporation will occur and no cooling effect will occur; that is one of the primary purposes of air conditioning is removal of moisture from the air. Remember, for every pound of moisture removed from the air, about 1000 BTU is removed.

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#4

Re: Does a ceiling fan cool a room?

08/10/2007 6:34 AM

I understand that air movement promotes cooling, both convective and through the latent heat of evaporation (of sweat). But why move the hot air (hot air rises) back down to where you are? Thinking about it, I'm not even sure which way they're designed to run! Never fitted one.

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#6
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Re: Does a ceiling fan cool a room?

08/10/2007 7:56 AM

Hi Wrenched,

ceiling mount fans have a control that allows you to choose which way you want it to run, and at what speed.

I have hot / cold AC at home, and a ceiling mount fan in my living room. I bought it cause it looks nice, but also for making AC more efficient in winter and summer (by making it run at slow speed in one or the other direction).

But why move the hot air (hot air rises)...

No idea how much hotter the air is close to the ceiling, but once the fan is running air temperature will get even.

On the other hand, it is proved that the air put into motion by a fan make you feel much more comfortable, just for improving evaporation of sweat.

Ideal speed of air when working is below 0,55 m/s, cause at higher speed papers on your desk start flying away!

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#47
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Re: Does a ceiling fan cool a room?

08/13/2007 6:18 AM

Cheers doc! Wonderful, this internet, conversing with people in such exotic locations!Good for the imagination, I have a wonderful mental picture of your desk now!

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#48
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Re: Does a ceiling fan cool a room?

08/13/2007 8:04 AM

...conversing with people in such exotic locations!

Hi Wrenched,

This is one of the great things of the internet!

I always wondered how it is to live in an exotic country like UK !

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#49
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Re: Does a ceiling fan cool a room?

08/13/2007 8:25 AM

I doubt that this stuff is as good as the real deal, but it's in the back of my mind for when I'm considering a meal out in London next time. All I need to do is re-check some back-waters of CR4 and I can ask for something really tasty, with expert recommendation ! Yep, I'll just tap 'beef' into CR4 search and get a whole bunch of info. Shortly after that chat on 'who has the best beef' I opened a Sunday paper to find some writer raving about the amazingly good Argentine beef to be found in London. Don't recall the name of the venue, but it looked . Yesereee, CR4 has all the answers. If I get round to it I'll send you a review. My next appointment is with a bit of Scottish beef, but I'll be sure to scoff lots of both before comparing. It may take many sampling trips.

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#51
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Re: Does a ceiling fan cool a room?

08/13/2007 11:48 AM

I doubt that this stuff is as good as the real deal

It is probably as good as the Irish pub in Buenos Aires!!!!!

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#53
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Re: Does a ceiling fan cool a room?

08/13/2007 3:24 PM

Surely not ? Our Irish chums seem to get everywhere - very handy when you want a fun time. Much as I like a good pint, it's the general atmosphere that makes for a good night out.

I'm still looking for the bar on CR4, there's got to be one somewhere - everything else is in place !

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#50
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Re: Does a ceiling fan cool a room?

08/13/2007 10:52 AM

Doc, its great living here in the UK the real ale is superb....

the food is mainly Chinese, Indian and Fried Chicken with a few burgers thrown in...

Plus there is always something to talk about.... just ask an Englishman anythink about the weather and you will be enjoying a chat for hours!!!

John

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#7

Re: Does a ceiling fan cool a room?

08/10/2007 9:01 AM

In answer to the question if you have a sealed room with no energy transfer in or out of it, yet you are supplying power into it to drive a fan then the room will heat up.

The only purpose of a fan, as others have said, is to help cool the skin by evaporating the moisture from it...

John.

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#20
In reply to #7

Re: Does a ceiling fan cool a room?

08/11/2007 9:36 AM

That's not the only purpose of a fan. Check out this link if you wanna see a fan involved in something really funny.

http://www.unoriginal.co.uk/footage1_3.html

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#21
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Re: Does a ceiling fan cool a room?

08/11/2007 9:39 AM

Oooowwwwwwwww don't let Del see that!!!

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#22
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Re: Does a ceiling fan cool a room?

08/11/2007 9:45 AM

My greatest apologies to Del if this happens to be a member of his family but it did make me chuckle.

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#8

Re: Does a ceiling fan cool a room?

08/10/2007 10:15 AM

Thanks to all. Since we all agree the inefficiency of the fan only raises the room temperature in a closed room. However, it does cool a sweaty person. So..why run fans all day in an un-occupied facility?

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#9
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Re: Does a ceiling fan cool a room?

08/10/2007 10:31 AM

Hmmmm semi-retired, could it be something to do with the fact that flies like the still air in a room, and will congrgate in the centre?

Now with a circulating air pattern maybe the flies don't like it and go elsewhere?????

Just a random thought!!! - John.

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#26
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Re: Does a ceiling fan cool a room?

08/11/2007 10:45 AM

"Since we all agree the inefficiency of the fan only raises the room temperature"

Neither the inefficiency nor efficiency of the fan have anything to do with the fact that the motor is contributing all of its energy into raising the temperature of the air in the room!!

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#44
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Re: Does a ceiling fan cool a room?

08/12/2007 4:13 PM

So..why run fans all day in an un-occupied facility?

No reason at all ! It's a waste of money! Probably just too lazy to switch 'em off.

(Don't s'pose they take a lot of power)

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#10

Re: Does a ceiling fan cool a room?

08/10/2007 11:48 PM

The ceiling fan should push the warm air down in the summer to create an evaporative cooling breeze on the skin.

In winter the fan should pull the air up in the center of the room and circulated to and down the wall to pick up warm air from registers or radiators to move to center of room and up all over again.

You can save the energy consumed by turning it off, along with lights and other appliances when going out.

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#28
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Re: Does a ceiling fan cool a room?

08/11/2007 12:33 PM

Hi SS,

You said "The ceiling fan should push the warm air down in the summer to create an evaporative cooling breeze on the skin".

Looks to me like the fan should still pull the air up from the floor since the cooler air tends to congregate at the lowest level. The evaporative cooling should still take place but perhaps a little more efficiently than hot ceiling air being blown down on the occupant.

I think a horizontal oscillating floor fan would cool the occupant(s) a little better than a ceiling fan.

-John

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#29
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Re: Does a ceiling fan cool a room?

08/11/2007 12:53 PM

"Looks to me like the fan should still pull the air up from the floor since the cooler air tends to congregate at the lowest level. The evaporative cooling should still take place but perhaps a little more efficiently than hot ceiling air being blown down on the occupant."

John: It seems to be counter intuitive. If you do not have a ceiling fan then you can't test the premises. But when all else fails -- "Read the Instruction Book"

e.g. Ceiling Fan Rotation SS

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#33
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Re: Does a ceiling fan cool a room?

08/11/2007 2:03 PM

I stand humbled. I cannot argue with Bob Vila.

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#39
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Re: Does a ceiling fan cool a room?

08/12/2007 4:15 AM

LOL

I think I'd almost pay to hear Bob explain things like Helicopters and Left-handed screwdrivers.

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#43
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Re: Does a ceiling fan cool a room?

08/12/2007 5:54 AM

If the room is closed, it hardly matters which way you do it and moving one away causes the other to take its place.

If a door or window is open, that might not be the case though.....

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#11

Re: Does a ceiling fan cool a room?

08/10/2007 11:54 PM

Another way to look at it is wind chill. Moving air across your body will seem cooler than it actually is I guess because more body heat is given up to passing air in a fixed amount of time than if the air is motionless. This is regardless of whether it is perspiration or convection.

If you are not at home there is no point in running the fan unless you want to cool the furniture which might in fact absorb some small amount of radiated heat from the room to some extent although I would make no claims as to its efficiency since running the fan generates heat. Since your body temperature is 98.6 more or less, the most efficient use of the fan would be only when you are at home.

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#12

Re: Does a ceiling fan cool a room?

08/11/2007 12:46 AM

It generally HEATS a room:

By pushing Hotter air- normally remaining at ceiling/roof level(because hot air is lighter than cooler air)

Temp. will RISE.

<Is it wise> NO!!

-Opposite of WISE is:??

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#13

Re: Does a ceiling fan cool a room?

08/11/2007 2:26 AM

Is it wise to run a fan if no one is home?

Only if you want to waste electricity and increase fire-risk.

Walk through most cities at night and you'll see plenty of fully lit offices etc. The claim I've usually heard is that they are left on for Cleaning Staff (!). I think that Cleaners can work a switch as good as anybody else. Maybe fans and lights should be switched via motion sensor or something at night. It's not unlike the issue of leaving home gadgets on standby when not in use.

Disclaimer : If the fan is solar powered you can run it at night without worry.

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#14

Re: Does a ceiling fan cool a room?

08/11/2007 2:35 AM

I got the answer immediately to this question when I was confronted with the same question at Saudi Arabia when I was a young engineer of 23.The answer is simple and must be known by all mechanical engineers who studied heat transfer.

1)The fan does not cool the weather,however,it heats up slowly because of the heat dissipating from the friction in the engine,propellers and bearings of it.

2)If the room weather is less than 36 degree C,the circulating air will increase the heat transfer from your body to the room because of mainly forced convection(when the fan is working)-which is at least 10 times more than the heat transfer during natural convection(when the fan is stopped).Thus increasing the heat transfer from your body to surrounding highly and cooling your body rapidly depending on the temp of the room.The cooler the room,the higher cooling rate of your body.

3)However,if the room temp is above 36deg C,the heat transfer will be just the opposite- to your body from the room at highly increased rate because of forced convection again.In this case there is no cooling effect-worse is the heating effect is highly increased which may lead to some kind of breakdown in the person again depending on the tenp difference between the room and yr body.

The other effets are minor.

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#15
In reply to #14

Re: Does a ceiling fan cool a room?

08/11/2007 3:13 AM

Dear All,

It seems the hot air is attracting a lot of the team . Here's one simple answer you may ponder about. Whatever you may say , I am sure it works and consumes little energy that is not renewable.

I suggest that whoever is worried about the doors and windows which may be closed the best way to avoid the increase of the ambient temperature is as follows:

1.Drill a hole in the top of one of the walls,

2Through it place a suitable lenght of good manila or other rope,

3.At the end of the rope and to the under side of the ceiling install a simple "panka" made of suitable material,

4.Recruit a young and energetic person (male or female)it is suggested, here that you might have a team for day and night duties,

5.Sit one of the above on a stool, outside the room, and have him pull on the cord at rate of about once every two minutes. If the material of the "panka " has been well calculated it will move the required amount of air (hot or cold).

Labor

NB For "purists " I note here that I have seen these with electric motor which mechanises the simple but very effective system (the electric motor is generally outside the room)

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#17
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Re: Does a ceiling fan cool a room?

08/11/2007 6:38 AM

Your comments fit into my personal observations, that I was too timid to mention, thanks.

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#19
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Re: Does a ceiling fan cool a room?

08/11/2007 8:21 AM

Aww, c'mon Andy. Don't be shy...I'm gonna hide out down here 'till it dawns on me.. Don't say the 'timid' word or Del might hear and scent mouse.

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#23
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Re: Does a ceiling fan cool a room?

08/11/2007 10:00 AM

...why are you always right?????

Exit stage right before Del arrives......

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#40
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Re: Does a ceiling fan cool a room?

08/12/2007 4:37 AM

LOL

"Cheque please...."

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#16

Re: Does a ceiling fan cool a room?

08/11/2007 5:43 AM

The average temperature will be raised slightly by the fan.

You are expending energy into the movement of the air plus there's the waste heat from the motor.

It's not wise to run anything you don't have to if no one is home.

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#18

Re: Does a ceiling fan cool a room?

08/11/2007 7:17 AM

At first, at least, it depends on where the thermometer is. Or, you can save the power and just move the thermometer...to change temp of the room.

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#24

Re: Does a ceiling fan cool a room?

08/11/2007 10:01 AM

Does a ceiling fan cool a room? = NO

A ceiling fan does not cool a room - it can cool a person but only if they are sitting in the air flow (wind across person = wind chill)

Is it wise to run a fan if no one is home? = NO

It heats a room slightly by remixing hot air that has risen to the ceiling (stratification) and also adds a small amount of heat from the motor.

=======================================================

NOTE: An exhaust fan is a different question with completely different variables.

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#25
In reply to #24

Re: Does a ceiling fan cool a room?

08/11/2007 10:26 AM

If you sit very still in a room with no air movement, as you sweat and your sweat evaporates, you will accumulate a cloud of 100% saturated air in your vicinity--air that can contain no more moisture. The sweat will no longer evaporate and you will feel uncomfortable as the sweat drips off of your body. If you slowly move the cloud away from your body (or your body away from the cloud) you will momentarily feel a little better, a little cooler, because the local air will allow a bit of sweat to evaporate from your body. Then it becomes saturated and you feel uncomfortable again. A fan moves the air around so that the air close to your skin does not become 100% saturated with water vapor until ALL of the air in the room is. But the fan has an additional effect--it adds ENERGY to the air. The more energy in the air, the more moisture it can contain. Hot air can hold tons of moisture. Cold air cannot hold much at all. You could actually make the room more comfortable by heating it up a little--the air would no longer be saturated and your sweat would evaporate and you'd feel cooler. Adding energy to the air can also take the form of moving it around. Air in motion can hold more moisture than air that is still. When you air condition a space on a Navy ship, the steam heating coil in the vent is always downwind from the chiller water coil so that when the air is chilled, it can then be warmed up a little. This reduces the relative humidity so that the body's natural cooling mechanisms will work better. Simply chilling the air will not improve its ability to absorb evaporated sweat. It will leave the chiller coil at 100% relative humidity. If you don't warm it a little, the air coming out of the vent will feel clammy and in spite of the fact that it might be cool, people will find themselves sweating through their uniforms because their sweat can't evaporate. So turn off the fan when you leave the room. The fan is running only for your comfort and if you're not in the room, it is serving no purpose. I have an electrostatic precipitator in my bedroom that removes dust from the air. I don't know if it's necessary, but I like to run a fan to make sure all of the air is circulating near the precipitator for cleaning. The precipitator has a fan of its own, but it is not very powerful and I'm skeptical that it can circulate all of the air in a room.

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#30
In reply to #25

Re: Does a ceiling fan cool a room?

08/11/2007 12:58 PM

I knew someone would get to the evaporation break point. I think rbixby has worked outside in hot humid weather.

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#31
In reply to #30

Re: Does a ceiling fan cool a room?

08/11/2007 1:17 PM

Well............inside in a hot humid environment. Shoulda finished the post.

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#32
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Re: Does a ceiling fan cool a room?

08/11/2007 1:19 PM

Hi Pepper: It happens in every thread. Once the original question has been answered, there are always those [rbixby ?] who have to have their say whether it is to the point or not.

Have a nice week end. SS

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#34
In reply to #32

Re: Does a ceiling fan cool a room?

08/11/2007 2:17 PM

It's a complex question and the answer goes beyond the parameters of the original statement. I didn't mean to be impertinent, but I was steeped in this kind of thing in the military and no one had brought all the corners of the conceptual hanky together to form an all-encompassing ditty bag.

I'm a newcomer here and I haven't learned all the unstated rules about how far to go in answering a question. Would it have been preferrable to say, simply, "No."?

Plus, I've discovered that some of the ideas and concepts I've been spoon fed over the years don't stand up to inquiry and it's educational to me to be challenged and to be told when I'm flat-out wrong about something. If you're careful and restrained in how you respond to a question, your inaccurate or half-understood intellectual foundations can stand for a long time before some unexpected situation crushes them. You have to re-inspect your underpinnings constantly or your rush hour commute might end up at the bottom of the Mississippi.

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#36
In reply to #34

Re: Does a ceiling fan cool a room?

08/11/2007 3:52 PM

Hear hear rbixby, we should all keep an open mind and not think we know it all etc...

All too common these days when someone questions anothers view is for the response to be argumentative, but your response shows you are willing to listen to others views and question your own, which in my book means a damn sight more respect to you....

John.

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#38
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Re: Does a ceiling fan cool a room?

08/12/2007 2:45 AM

Well stated, no problems for me.

There are a lot of CR4 people who take umbrage if you tell hem that their Baby is ugly.... they tend to react in a most juvenile manner at that point....

I am not picking anyone out, as you usually don't need to, they stand up all on their own to be counted.........wait up!!

Have a great day and stay as you are...

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#41
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Re: Does a ceiling fan cool a room?

08/12/2007 4:42 AM

Hear,hear ! I just gave rixby a vote, and can see that either your good self or Electroman has not done so yet. At present he has 2 'plus' votes. Voting twice doesn't work (I already tried it ).

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#42
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Re: Does a ceiling fan cool a room?

08/12/2007 5:50 AM

Good point, thanks for that. I will also vote.

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#54
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Re: Does a ceiling fan cool a room?

08/13/2007 9:59 PM

It heats a room slightly by remixing hot air that has risen to the ceiling (stratification) and also adds a small amount of heat from the motor.

... and adds heat through increased molecular motion as well. You may remember the physics experiment in which you shake a vial of bb's.

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#55
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Re: Does a ceiling fan cool a room?

08/14/2007 2:23 AM

I know it's not your quote Ken, but why do we always say 'hot air rises' and not 'cold air falls'. I'm sure that poor old gravity would feel marginalized by the former expression.

Whilst I'm being completely inane, a 'vial of bb's' sound like the collective noun for younglings when dribbling from each end. euchh.

Soreee !It's early morning here, and the caffeine levels are not high enough yet.

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#56
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Re: Does a ceiling fan cool a room?

08/14/2007 4:54 AM

I think that he was implying "Ball Bearings"......correct me if I am wrong please.

When shaken hard for 10 minutes or so, they become quite dramatically warm to the touch....

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#57
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Re: Does a ceiling fan cool a room?

08/14/2007 9:26 AM

LOL. When I googled "bb" just now I got this. I am now even more sure that it has something to do with nausea !

Gawd, the things ya see when you ain't got yer BB gun.

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#58
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Re: Does a ceiling fan cool a room?

08/14/2007 9:32 AM

AAAARRRRRGGGGHHHHHH! The Spanish are crazy for this type of junk! Makes me want to walk the Gobie!

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#59
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Re: Does a ceiling fan cool a room?

08/14/2007 9:47 AM

Yes, I understand the pain. I think I'd sooner eat the Gobi than watch that kind of thing.

I only just noticed, but when in the 'collapsed' state, only about 10 % of your "Brain" appears by your Avatar Mr Truman ! How many others have had this happen to them, and what parts have been lopped off !. You are fortunate to function on 10 % - I fear that some others might struggle even with 90 % working. Being completely mad, and short of nomenclature, I am free from such worries.

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#60
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Re: Does a ceiling fan cool a room?

08/14/2007 9:53 AM

LL

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#61
In reply to #55

Re: Does a ceiling fan cool a room?

08/14/2007 1:47 PM

I know it's not your quote Ken, but why do we always say 'hot air rises' and not 'cold air falls'.

The saying is from politics, where rising to the top of the power structure requires nothing but hot air.

Whilst I'm being completely inane, a 'vial of bb's' sound like the collective noun for younglings when dribbling from each end. euchh.

What a vile vial.

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#27

Re: Does a ceiling fan cool a room?

08/11/2007 12:20 PM

The room temperature will rise slightly. The fan is useful only if a person is in the room; it will generally make them feel more comfortable.

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#35

Re: Does a ceiling fan cool a room?

08/11/2007 2:21 PM

It kind a makes you wonder how far a tread can go after watching how far a question about a ceiling fan has gone ....................... love it

........ ...........................

... .............. . ........................

What is "Void-Ware" ............ and why is it prohibited.................... ¬

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#45

Re: Does a ceiling fan cool a room?

08/12/2007 10:00 PM

No. A fan cools you down by blowing air against you to evaporate away your sweat. Likewise, a cooler fan for a microprocessor works by blowing air at a lower temperature towards the processor so that the air can carry away the heat.

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#46

Re: Does a ceiling fan cool a room?

08/13/2007 2:22 AM

If you hang your washing to dry in the room with the fan going, you could have a cooler room when you return; provided the humidity is low it may be a good idea. I often use my ceiling fan to dry my clothes; but the primary objective is not to keep the room cool and so I leave the windows open.

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#52

Re: Does a ceiling fan cool a room?

08/13/2007 12:25 PM

The ambient temp in a sealed room would rise due to the heat produced by the motor.

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#62

Re: Does a ceiling fan cool a room?

08/15/2007 9:04 AM

All explanations below are rigth to the point of relevance and totally correct. Putting all together the celling fan will make your A/C to work better by keeping the air flow and humidity in a constant basis. At the end of the day, running the fans while cooling or heating will help the unit pump to run smoothly, that's the main reason to have celing fans in houses. The roof and floor temperature difference will accumulate condensation in the inside rooms, if no extra help for A/C unit the energy consumed will go up to 8% - 10% (make your money calculations considering that is better to replace a celing fan that a A/C unit).

The use of a celing fan when the fire place is lit, will also help. Not to mention that my wife uses those blessed fans after she burned supper.

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