changing fan blades to get quieter condenser operation

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Old 07-13-13, 12:29 PM
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changing fan blades to get quieter condenser operation

Hi

i have a Ruud unit (Model UAMB-030JAZ, '01), and last August the fan motor went out on the condenser unit. I had a guy fix it, and he did using an AO SMith Model # F48T12A01. I think he used the same 2 blade fan, but when he put it all back together the fan blade itself was making more noise, as though perhaps he had bent it a bit.

Finally, the noise has driven me to distraction and I started looking into changing the motor and the fan blade, and then encountered not only suppliers who will not sell to me (in Houston), but an amazing paucity of information (or at least it hard for me to find), and there is a technical problem. I understand that i can get a somewhat more quiet motor (maybe 5 db, with a sleeve bearing), and that a 4 blade fan will be quieter b/c of lower pitch of the blades.

But as i read it became clear there is a technical problem: if the CFM not within some range (i cannot figure out which range) then things with the entire unit get wonky. So, it seems to me the solution is to find the CFM for the unit and replace it with a motor and 4-blade fan that produces the same throughput of air.

My question(s): is that an accurate way to think about it, and if so, how can i figure out which motor and fan-blade? any suggestions for making it quieter (apart from sound panels, and wraps of various kinds)? Can you straighten me out on the issue?!

thanks very much in advance!

john
 
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Old 07-13-13, 12:41 PM
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Welcome to the forums.

is that an accurate way to think about it ?
Yes it is but without having the expertise of an engineer it could be un-obtainable.

The manufacturers don't allow any modification to their units so they won't help you. You aren't going to find the CFM rating of the factory fan.

Without installing a new motor and fan blade set.... you won't know what CFM they'll deliver or if they will cool the unit properly. It would appear to be an expensive trial and error experiment.
 
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Old 07-15-13, 05:18 AM
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Thanks very much for your response.

I found this document: http://www.aepsurplus.com/upload/att...2_147_rev9.pdf

Am i correct to read it as saying the 030JA, which is the model i have, has CFM of 1960 (on page 6)? If that is the rating of the factory fan, then i just need to find the rating of the aftermarket fans, right? Any ideas about that?

thanks again
john
 
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Old 07-15-13, 05:30 PM
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the speed and blade pitch determines the cfm. It was designed to obtain that and should not be changed from OEM in anyway. If you do, you will adversely affect the cooling capacity of your unit.
 
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