Designing Ceiling fans.

[RMERMP]

Good day!

Please help me design ceiling fan for a 800 sq.ft classroom. Im confuse of what fpm to be use for this room since ASHRAE permits less than 50fpm for comfortable air velocity in a room. and this is the first time i will be design ceiling fan. thanks

 

[BrianPetersen]

Why not just go to Home Depot and buy one?

 

[BUGGAR]

I suggest it would depend on the age of the occupants using the classroom. If they are under ten years of age, you will want to keep the fans well above their heads. If they are fourteen to eighteen years of age, you will want to place the fans low enough to just catch them upside their heads.

Seriously, fans have adjustable speeds and are reversible so you don't blow directly on occupants.

 

[dbill74]

The velocity at the fan itself can be more than 50 FPM since it will slow and the flow diffuse as it gets further from the fan. But ASHRAE is correct, 50 FPM at occupant level is about the maximum you want to see at that point. For one, you won't get complaints of drafts, second is at 50 FPM you aren't going to be blowing papers off desks and such.

Generally speaking, you can feel 75-100 FPM on your skin and you are going to start blowing papers around.

Get with a ceiling fan manufacturer, they can help you select an appropriate fan for your application. If the ceiling is sufficiently high and you want to use a single fan, Big Ass Fans specializes in this type of fan.

I also recommend googling "ceiling fan air flow patterns". Study the pictures and read through the white pages it brings up.

 

[RMERMP]

Thanks guys. Great help. i used 10 fpm to compute my cfm requirement, since they required 4 orbital ceiling fan per classroom i used the formula CFM/AREA = FPM. it resulted to 2000cfm per 1 ceiling fan. can this ceiling fan achieve a comfortable throw for the occupants?

 

[racookpe1978]

Have you gone to the hardware store and read the (dozens of) fan box labels?

They HAVE cfm and room sizes listed! (Hint: Big room, public room = ONLY remote fan controllers or wall-side controller/veriable speed switches, NOT hanging chain pulls!)

 

[dbill74]

What fan is "this fan"?

It sounds like you have and know your requirements for the fans. Now you need to do some leg work, talk with some sales reps, and search manufacturer's engineering data in catalogues and online to find a fan that meets your requirements.

PS) That is your job.

 

[chicopee]

You may not be aware that, for example, Dayton, a manufacturer of ceiling fans publishes graphs of fan performances . These graphs will show air velocities vs. distances from the fan centers. Normally these graphs are not provided unless specific requests are made to the suppliers. In my case, my graphs are for 60" ceiling fans industrial fans much too big for your classroom application.