What determines how fast ceiling fan spins?


  #1  
Old 07-28-21, 06:33 PM
B
Member
Thread Starter
Join Date: Jul 2005
Location: Pennsylvania
Posts: 584
Received 5 Upvotes on 4 Posts
What determines how fast ceiling fan spins?

So over the years I've installed a total of 5 different ceiling fans throught our home. What I don't understand is how some of them spin really fast and blow alot of air. While others don't. Is it wattage, amps, CFM rating? Or just something I did wrong. I have all of them installed on speed switches with 3 different power levels. Just something that's perplexed me for over 10 years now.
 
  #2  
Old 07-28-21, 06:45 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,775
Received 4,122 Upvotes on 3,702 Posts
It's all in the design. Blade size and pitch. Motor hp and speed.

One would think that the larger blades would create more air and normally they wood except if they're too close to the ceiling where they work opposite. The fan needs the ability to draw air over the blades to discharge down. I've seen the best air movement from smaller fans.

I have a 52" Hunter five blade custom ceiling hugger in my bedroom.
You wouldn't believe the noise it makes when the blades starve for air.
Overall..... I'd consider the air movement poor.
 
  #3  
Old 07-28-21, 07:05 PM
H
Member
Join Date: Nov 2012
Location: USA
Posts: 2,321
Received 297 Upvotes on 255 Posts
We're in an old farmhouse with window A/C, so 3 bedroom ceiling fans, den, kitchen and sunroom.

Agreed on motor HP, how many blades, how close to the ceiling.

I'd ALSO add that the pitch can make a big difference as well- both for balance, and air movement.
So, what I've done a few times is put an additional twist on the blades so they "bite" more air, which slows down the rotation a bit.
However, I've also had some which worked MUCH better taking 'shallower" bites of the air, and tossing it down at higher velocity.
 
  #4  
Old 07-29-21, 04:35 AM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 10,970
Received 729 Upvotes on 644 Posts
With reference to what PJ posted. For awhile they stopped making ceiling hugger fans just because of that problem. But people were not buying the fans because their rooms could not handle the drop tube. So the lesser of the two evils is poorer performance but the ability to have a fan in typical 7 to 8 foot bedroom ceiling.
 
  #5  
Old 07-29-21, 08:22 AM
B
Member
Thread Starter
Join Date: Jul 2005
Location: Pennsylvania
Posts: 584
Received 5 Upvotes on 4 Posts
interesting stuff. didnt think about the closeness to the ceiling. Not all of mine are just not spinning very fast. the one in my sons room really cooks. whereas the others, different brands and models, spin not as fast.
 
  #6  
Old 07-29-21, 09:47 AM
H
Member
Join Date: Nov 2012
Location: USA
Posts: 2,321
Received 297 Upvotes on 255 Posts
If you have several fans, (especially by the same manufacturer), you sometimes get lucky and can swap the blades between fans- the ceiling-hugger style seems to work better with longer blades, while the drop-fans can work with shorter blades.
 
  #7  
Old 07-29-21, 01:00 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,775
Received 4,122 Upvotes on 3,702 Posts
The manufacturers put out recommendation charts but we all know bigger is better.
When I replace mine I'll use a much smaller diameter fan.
 
  #8  
Old 07-29-21, 01:52 PM
Norm201's Avatar
Member
Join Date: Sep 2013
Location: United States
Posts: 10,970
Received 729 Upvotes on 644 Posts
But the smaller size fans also make more noise, especially at the high speed.
I have a 52" in our bedroom. Wife does not like the fan, but I do. At low speed it drives just enough air that I can feel it but she is willing to put up with it. Also very quiet at the low speed.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: