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Old 06-01-2009, 08:01 PM   #1
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how many cfm is mystery ac unit pushing


I'm trying to figure out the cfm rating for a central air unit fan. this unit was given to me and has no paperwork. There is no manufacturer printed but i have a model of B20-36 also a b/m number 8041-1-3a it is 6.3 amps and 1/3 hp. the output is about 14x 11 3/4 what i believe is called a centerfugal(sp?) fan, blades are about a foot tall. any info anyone can provide is greatly appreciated even guesses for manufacturer would be great.
Yes i know this is a strange question and not the right way to do things.

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Old 06-01-2009, 08:05 PM   #2
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how many cfm is mystery ac unit pushing


Quote:
Originally Posted by Scottydog0147 View Post
I'm trying to figure out the cfm rating for a central air unit fan.
it is . . .1/3 hp.
the output is about 14x 11 3/4
blades are about a foot tall.
CFM is related to power draw and duct size.
Look in paper or Web catalogs that do show CFM for units comparable to yours in size, fan config. and power draw. This will get you within a few percent of what your unit does; they all have to follow the same laws of physics. You want "the fan curve".


Last edited by Yoyizit; 06-01-2009 at 08:08 PM.
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Old 06-01-2009, 08:25 PM   #3
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how many cfm is mystery ac unit pushing


The amp draw you posted, is more amps then a 1/3HP motor draws weather its a 120volt, or 240volt motor.

In the 3/4HP range for a 120volt motor.
Close to 2 HP for a 240volt motor.
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Old 06-01-2009, 08:54 PM   #4
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how many cfm is mystery ac unit pushing


Sounds like it might be an exhaust hood fan, typically found in a restaurant.

Does it look like this?

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Old 06-01-2009, 09:13 PM   #5
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how many cfm is mystery ac unit pushing


Thank both of you for your speedy replies. plate says 115v, of course the numbers don't make sense (story of my life) but i assure you that is what the plate says. amp 6.3 min fuse 8a (i'm running 12ga to it anyway) any thoughts to who made it?
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Old 06-01-2009, 09:14 PM   #6
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Originally Posted by AndrewF View Post
Sounds like it might be an exhaust hood fan, typically found in a restaurant.

Does it look like this?

thanks i needed that laugh
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Old 06-01-2009, 09:15 PM   #7
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how many cfm is mystery ac unit pushing


Post a photo of that bad muvva'.
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Old 06-01-2009, 09:16 PM   #8
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how many cfm is mystery ac unit pushing


Heh, well when you said the blades were 1' tall, I remembered that these units have blades that are tall At least the one I had in my shop for awhile.

I will admit, I've never seen one used in a house thought.
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Old 06-01-2009, 09:43 PM   #9
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This link [table 430.248] shows current draw for a 1/3 hp motor but probably 95% of these motors draw less than this
http://books.google.com/books?id=DDs...um=4#PPA121,M1
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Old 06-01-2009, 10:06 PM   #10
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sorry i don't think i was quite clear on what i'm talking about, the correct term is air handler. the indoor unit, all i can find is complete air handlers with the fan and evap not just the fan in a box. sorry that centrifuge thing probably threw everyone off. american standard, trane, lennox, carrier none of them have anything specific on their site any direction i should go to find just a fan and it's specifications?
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Old 06-01-2009, 10:12 PM   #11
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how many cfm is mystery ac unit pushing


http://www.google.com/search?hl=en&s...&aq=f&oq=&aqi=

http://www.google.com/search?hl=en&s...&aq=f&oq=&aqi=

http://www.google.com/search?client=...UTF-8&oe=UTF-8

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