Outdoor ceiling fans

[MrFixIt]

Hi

Hi Ian, no apologies necessary!! and thanks for your information.
I have included below a picture of how it was installed and I am guessing you ARE RIGHT!!. Guess you will be keeping your body bits
What do you think?

THIS is NOT going to work!

All you are achieving HERE is recirculating the ALREADY HOT air. You would be better off not having any fans than having such a high fan position.

You are in the "same boat" as all other people that have such pergolas installed. No one seems to realise how much hot air is trapped in such a pergola. PLUS you have the metal roofing continually radiating heat down on to YOU AND THE FANS.

Pergola "designers" (using the term LOOSELY ) DO NOT allow for air flow and consequenlty you have the resultant problem.

The problem will easily be resolved if you can "release" the trapped hot air.

I built my own timber pergola and lined it (above) with alsynite and then placed shade cloth over the alsynite then timber battens over that at 50mm spacing. This provides 50% shade over the 70% shade cloth which all covers the alsynite "weather proofing".

At the ridge I installed a long strip of waterproof shadecloth, ie there are no holes in this piece of shade cloth, it's like a piece of plastic sheeting with the shadecloth "molded" in it.

This strip covers the top edges of the alsynite to make it waterproof, HOWEVER the hot air can escape from under the ridge as it flows out past the alsynite. This is probably hard to understand or visualise, but it works exceptionally well for me. My pergola always stays cool underneath and is fully waterproof.

I could take some photos or draw the construction method for you if you need it, but as my pergola is timber it does not really apply in your situation.

If you can discretely mount a "whirlybird" somewhere, this will provide a much better solution to the air flow and will cost you nothing to run

HTH
.

[Ian Smith]

Oh, for Chrissake!!!
The freakin' fans are too close to the freakin ceiling !!!

They DO NOT circulate any air, hot or cold, because the turbulance caused by the blades being too close to the ceiling causes them to become inefficient.

You could put as much insulation as you like up there and let as much hot air out as will escape (although some seems to have become trapped in this thread!!) but those bloody fans will not work well until they are lowered away from the ceiling to the minimum manufacturers specification.

If the bloke who fitted the fans initially had done it correctly then MAYBE Madrat might be complaining about HOT air being pushed around but right now she doesn't even get that.

Ian

[patty]

Absolutley 100% correct Ian you dont have to be Einstein to work out why this fan is not pushing any air around from where you sit or stand, cause the freakin fan is 3 mtrs above you, the Spark should have suggested to put a rod drop on it it is just pure common sense from a Sparks point of view but obviously he didnt and he probably didnt want the hasssle of going to a wholesaler and geting one possibly cutting it down and drilling and fitting it which does add extra time to the job in my experience i have always had to order these in I would say he ran the gauntlet just installed it hoping the customer would be happy with the job collected his money and on his way to the next one!!

Madrat did you buy the fan or did the spark supply? as the lighting shop or wherever you bought it from should have asked you questions about the install and should have suggested a rod drop also!

[patty]

ps The more i look at that picture it would have to be more like at least 4 -5 mtrs to from ground level to the bottom of the fan when it should be roughly between 2.3 and 2.6 max for max effiency pending obviously on the location

[madrat]

Well to me it is plainly obvious that the ceiling fan needs a rod drop on it by the looks of the pitch on the roof i would guess it must be nearly 3 mtrs to the bottom of the fan and you wonder why your not getting any airflow?you did mention your freind has the same fan installed by the same spark but does her pergola have the same pitched roof and the fan sitting so high up if no,its a no brainer get a rod drop!

Thanks for your 'input' Patty, however ceiling fans are not my expertise and nor do I pretend to know something I don't. Hence the reason why I was looking for 'advice' not criticism.

I was stupid enough to think that the sparky might know what he was doing!

It is with thanks to Ian Smith for his CONSTRUCTIVE & POLITE advice/suggestions that co-incided with what my husband was thinking.

WE bought the fans AND we bought the DROP RODS to go with them.

The sparky was left to install everything!

When I eventually saw the fans installed, I questioned him on why the drop rods were not used. His response was that it would hang too low.

I may be an idiot, but I do know these buggers can be cut down and redrilled to suit!

It came down to sheer bloody laziness on the sparky's part!! and then assured me that it would make no difference.

The sparky did not need any tools whatsoever, as hubby as the latest of everything on the market. Everything was supplied for him!

My friend's pergola is at a much steeper pitch and a lot higher than ours, which allowed his drop rod to fit without any modification.

We are now facing the fact that we were taken for a ride by the
sparky.

Have no intentions of wasting any time getting him back. We will cut our losses with the sparky and will definitely be trying Ian's advice before anything else.

Ian is correct, there is no hot air. There's no air at all.

We will lower the buggers and see how we go.

[MrFixIt]

Hi

Oh, for Chrissake!!!
The freakin' fans are too close to the freakin ceiling !!!

Goodness me Ian, what's your problem?

I expected a better response than such a discourteous reply, especially from a senior member!

They DO NOT circulate any air, hot or cold, because the turbulance caused by the blades being too close to the ceiling causes them to become inefficient.

Of course they circulate air. You have admitted as much in your statement above. You cannot have (air) turbulence WITHOUT air movement.

You could put as much insulation as you like up there and let as much hot air out as will escape (although some seems to have become trapped in this thread!!)

Unwarranted sarcasm.

but those bloody fans will not work well until they are lowered away from the ceiling to the minimum manufacturers specification.

Of course. I did not disagree with your original comments. I merely added some confirmation by stating

THIS is NOT going to work!

If the bloke who fitted the fans initially had done it correctly then MAYBE Madrat might be complaining about HOT air being pushed around but right now she doesn't even get that.

Yes, I agree.

The problem is not so much that the air doesn't circulate. The problem is the efficacy of the fans, ie the PERCEPTION of the air movement.

As the fans are mounted too high up (the point with which I agree), the air perceived air flow is minimal or as it appears (according to the op) the air flow is none existent.

There are other factors that may need to be considered. For instance, if the pergola has very little surrounding wall, eg the house or another wall etc, the fan will be operating in an almost infinitely sized room.

For a fan to be PERCEIVED to be working, ie the air flow can be felt and of course therefore cool the recipient there needs to be an air flow.

As you will no doubt appreciate, the air flow or circulation in a room will be much better than that in an outdoor area.

The height and or position of the fan will have a bearing on the cooling effect, be it real or perceived. The air flow "problem" alluded to above will be exacerbated by the heat radiated from the steel roof of the pergola.

What will happen is that the trapped heat will remain trapped at the ridge of the pergola roof. The level (or thickness) of this heated air will vary depending on the overall heat of the day. If the trapped hot air cannot escape then it will ultimately flow out around the eaves of the pergola roof.

This means that there will be a point at which the cool air will meet the hot air. It is obvious that the fan needs to be well within this cool air for the fan to be in any way effective.

The point at which the fan needs to be mounted is very likely to be too low to be safe, so the fan needs to be mounted high enough to be safe at which point the fan is then likely to be drawing its air flow from within the warmer air.

The air being drawn from this warmer air is not too likely to get cooler as it will be (re)heated by the radiant heat from the steel of the pergola roof.

What ultimately happens is that due to the lack of "walls" that can contain the cooler air at lower levels, the cooler air never gets "circulated" to the higher level. The nett result is a layer of hot air that just gets hotter, heated by the radiance of the steel roof.

The cooler air at lower levels needs to be "circulated" into the roof area. This can only be done by some means of releasing the trapped air. (hence my suggestion of the whirlybird).

If this hot air can be released, then the efficiency and efficacy of the ceiling fan, both perceived and real, WILL improve.

BTW, changing the number of fan blades from five to three would probably improve the circulation.

see this...

Blade surface area to air-feed ratio. In general, more blade surface area means greater airflow. However, if there is too much blade surface area, there will not be adequate space between the blades for air to be drawn through. Fans which have an unusually large blade surface area, such as fans with decorative palm-leaf-style blades or many fans with six blades, do not have adequate space between the blades for an unrestricted amount of air to be drawn through. This results in reduced airflow. The effect of this ranges from negligible to dramatic, depending on the exact dimensions involved. Contrary to popular belief, more blades typically does not equal more airflow. Most four-bladed fans move more air than comparable five-bladed fans spinning at the same speed; this is indeed noticeable on five-bladed fans which have an option to install only four of the blades. Also due to this effect, the overwhelmingly vast majority of industrial fans have three blades.

from... http://en.wikipedia.org/wiki/Ceiling_fan

.

[patty]

Apologies Madrat dont take it Personal hey!

Some Lite reading enjoy!


Bases for comparison

There are several factors which determine a fan's efficacy and efficiency. Each of these factors can be used as a basis for comparison when deciding between different candidate fans to purchase.
A fan's efficacy (in other words, its ability to generate airflow) is measured by its CFM (Cubic Feet of air moved per Minute) rating. The following factors all have an effect on a fan's CFM rating:

• Length of the fan's blades. The longer a fan's blades are, the larger percentage of a room's air volume upon which the fan will have a relevant impact. This factor is of greater importance in large rooms. The majority of ceiling fans come in one of three sizes (sweep diameter): 36", 42", or 52".
• Total surface area of the fan's blades. The greater a blade's surface area, the more air it is able to move. However, there can be "too much" surface area (refer to Blade surface area to air-feed ratio below).
• Pitch of the fan's blades. The angle at which the fan's blades are tilted relative to the X-axis is referred to as the "blade pitch". The steeper (greater) the pitch, the greater the airflow. Since increased pitch also means increased drag, only fans with well-made motors can support steep pitches. Cheaply-made fans typically have a pitch between 9 and 13 degrees. A pitch of 15 degrees and upwards is considered very good, with numbers in the 20s being the highest.
• Speed of rotation. The speed at which a fan rotates, measured in RPM (Revolutions Per Minute), directly correlates to the amount of air moved. Faster rotation equals greater airflow.
• Blade surface area to air-feed ratio. In general, more blade surface area means greater airflow. However, if there is too much blade surface area, there will not be adequate space between the blades for air to be drawn through. Fans which have an unusually large blade surface area, such as fans with decorative palm-leaf-style blades or many fans with six blades, do not have adequate space between the blades for an unrestricted amount of air to be drawn through. This results in reduced airflow. The effect of this ranges from negligible to dramatic, depending on the exact dimensions involved. Contrary to popular belief, more blades typically does not equal more airflow. Most four-bladed fans move more air than comparable five-bladed fans spinning at the same speed; this is indeed noticeable on five-bladed fans which have an option to install only four of the blades. Also due to this effect, the overwhelmingly vast majority of industrial fans have three blades.
• Height of the fan relative to the ceiling. If a fan is too close to the ceiling, the airflow is restricted; that is, the fan will not be able to draw as much air through its blades as it has the potential to do. For this reason, "hugger"-style fans (those which mount directly to the ceiling without the use of a downrod) are all inherently disadvantaged. The distance that a fan should be mounted from the ceiling is directly correlated with its air-moving potential; no fan should be mounted with its blades closer than 24 inches to the ceiling, however that figure is often far greater with industrial fans. Unfortunately, this is often impossible in household situations due to the fact that a minimum ceiling height of nine feet would be required to meet safety codes ("blades must be mounted a minimum of seven feet from the floor", and 8 or more feet is typically desired).

In addition to all of the aforementioned factors, there are certain other factors which have an effect on a fan's perceived efficacy (how efficacious an observer experiences a fan as being):

Note that this fan's blades are tilted relative to the Z-axis; that is, they are tilted upwards.

• Height of the fan relative to the observer. The closer the fan is to the observer, the more air movement the observer will feel. A fan mounted close to the ceiling in a high-ceilinged room will have a lower perceived efficacy than if it were mounted closer to the ground.
• Tilt of the fan's blades relative to the Z-axis. A few fan manufacturers, notably FASCO, constructed their fans such that the blades had an "up-tilt"; that is, they were tilted relative to the Z-axis (see picture at right). While this increased the area of the room over which the fan had a direct effect, thereby increasing the efficacy perceived by persons standing at the edges of the room, it decreased the airflow concentrated immediately under the fan, thereby reducing the efficacy perceived by anyone standing/sitting directly underneath it.
• Humidity of the room. Since a fan creates its cooling effect by speeding the evaporation of moisture (both sweat and ambient humidity) on human skin, its perceived efficacy is directly correlated with the amount of humidity (moisture) in the room. In dry environments, such as desert climates, a fan has a lesser perceived efficacy than in humid environments; this is especially notable during cold weather, where a humid environment has a pronounced wind-chill effect which is lacking in dry environments.

[Ian Smith]

MrFixIt,
My comments are born out frustration with the number of threads in the forum, this one included, which get a life of their own because respondents fail to read the original post correctly, and then go on to make their own assumptions and/or push their own agenda.

I (and you, and Patty) don't really know how high the fans are. Patty suggested 3 or 4 or 5 metres but that's a guess by him/her based on the photo supplied by Madrat who, incidently, hasn't confirmed or denied any of those numbers. Who knows how the photo was taken. Madrat may have stood on a table or she may have lain flatout on the floor. You're guessing and making assumptions.

The one thing that is known is that the fans need to LOWERED from their mounting point until they meet manufacturers specs, simple as that. Then Madrat can decide if they are working well enough The fact that this thread is now headed for over 20 postings just amazes me.

Wikipedia is not infallible and there are other factors to consider. If the following statement, in and of itself was true - "Fans which have an unusually large blade surface area, such as fans with decorative palm-leaf-style blades or many fans with six blades, do not have adequate space between the blades for an unrestricted amount of air to be drawn through. This results in reduced airflow. The effect of this ranges from negligible to dramatic, depending on the exact dimensions involved. Contrary to popular belief, more blades typically does not equal more airflow" then you'd better race out and tell Boeing to fit four bladed fans to all their jet engines and take of those silly things with lots of little blades.

Oh, and one last thing - turbulence obviously is air moving but not in any useful way - just look what happens when a boat prop cavitates, which is essentially what those fan blades are doing, because they too close to the ceiling - not because they are in hot air

Ian

[patty]

The fact that this thread is now headed for over 20 postings just amazes me.
But the kids love it Ian!

[madrat]

My apologies to everyone that I posted this thread.

It was not meant to cause havoc, I was merely asking for advice and suggestions on something that I am not familiar with.

I'll make sure to be mindful of what I post next time.

Ian, thanks for your suggestions and understand your frustrations with repetitive questions in threads. With the work that I am in, I am used to repeating myself

We will be sure to modify the existing fan to drop it down.

I would love to let you all know how it goes, but after today's postings, I am a little scared..

We'll see...................

[Ian Smith]

Madrat,
There's a lot to be gained from this forum from a lot of people who know an awful lot (I'm not one of them) - so please don't be discouraged.
You just have to learn to sort the wheat from the chaff

I think the best thing to do when you do post is provide as much relevant information as possible (that's a little hard I know if you don't know much about what you seeking info on) but put yourself in the place of the reader if that helps.

If you get an off-topic response then pull them into line and correct any assumptions - don't do as some have done and throw a cat into the dog-pound, never to be seen again - Christo and the too high patio comes to mind

Regards

Ian

[madrat]

Thanks Ian.

Unfortunately, when I am trying to obtain advice etc on something I just don't know about, I am really unsure as to what information is relevant until I am asked about specifics.

So, I guess to many people in the know of the subject, I appear to be an idiot.

I certainly don't want to gas bag about stuff that is totally irrelevant, so I apologise for the lack of info on the outset of this thread.

Appreciate your encouragement and hope to get my nerve back to continue with this one.

Cheers

[MrFixIt]

Hi

MrFixIt,
My comments are born out frustration with the number of threads in the forum, this one included, which get a life of their own because respondents fail to read the original post correctly, and then go on to make their own assumptions and/or push their own agenda.

I made NO assumptions and have NO agenda to push. I described how I did my pergola and how it differs greatly from the design of STEEL pergolas. In so doing I also conveyed how much more (heat) efficient timber construction can be. This (timber etc) aspect has not been further embellished by anyone and I was not and do not expect this to happen.

I (and you, and Patty) don't really know how high the fans are. Patty suggested 3 or 4 or 5 metres but that's a guess by him/her based on the photo supplied by Madrat who, incidently, hasn't confirmed or denied any of those numbers. Who knows how the photo was taken. Madrat may have stood on a table or she may have lain flatout on the floor. You're guessing and making assumptions.

PRECISELY, and that is why I DID NOT make any assumptions on the height of the fan. I only know that, as I have already agreed with you, the ceiling fan IS to close to the pergola roof.

The one thing that is known is that the fans need to LOWERED from their mounting point until they meet manufacturers specs, simple as that.

Yes, I (still) agree with you.

Wikipedia is not infallible and there are other factors to consider. If the following statement, in and of itself was true - "Fans which have an unusually large blade surface area, such as fans with decorative palm-leaf-style blades or many fans with six blades, do not have adequate space between the blades for an unrestricted amount of air to be drawn through. This results in reduced airflow. The effect of this ranges from negligible to dramatic, depending on the exact dimensions involved. Contrary to popular belief, more blades typically does not equal more airflow" [COLOR=Black]then you'd better race out and tell Boeing to fit four bladed fans to all their jet engines and take of those silly things with lots of little blades.

Ok, ok, lets not get carried away here. There are many different fan designs and these two are at completely different ends of the "fan" spectrum.

Oh, and one last thing - turbulence obviously is air moving but not in any useful way - just look what happens when a boat prop cavitates, which is essentially what those fan blades are doing, because they too close to the ceiling - not because they are in hot air.

Lets not go there, (cavitation) that's a whole other situation. We'll just stick to the "turbulence" theory, ok.

.

[MrFixIt]

Hi madrat

Unfortunately, when I am trying to obtain advice etc on something I just don't know about, I am really unsure as to what information is relevant until I am asked about specifics.

That's ok. If you don't know then by all means ask. We have ALL had to learn what we now know, by asking those that went before us.

So, I guess to many people in the know of the subject, I appear to be an idiot.

I don't think that and I doubt if anyone else in this thread thinks that. We do realise that you don't know "why" hence you asked the original question.

I certainly don't want to gas bag about stuff that is totally irrelevant, so I apologise for the lack of info on the outset of this thread.

There is really nothing to apologise for. Many people before you and many more to follow will ask a question and in turn be asked for more info. This is normal and is nothing to be concerned about.

Appreciate your encouragement and hope to get my nerve back to continue with this one.

Please don't feel discouraged, retain those "steely" nerves and reply with the end result. I am sure that all participants in this thread would like to know the outcome.

There's a lot to be gained from this forum from a lot of people who know an awful lot (I'm not one of them)

Having been making and fixing things since I was 8 years old and I'm now 58, after 50 years, I 'd like to place myself in the group of people that do "know an awful lot" Don't forget though, madrat, that I too had to ask questions or learn by trial and error, that's life's experience.

I look forward to your "next installment".

.

[davo_scuba]

Have we decided yet how high the roof is ? i've been reading through the posts and there is still no mention of the height of the roof ???Always a bit tempting to cut down to give you a bit more clearance being quite tall the internal fans normally have a bit taken off, less efficient yes, but the extra height is needed.