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Folks,
I've searched this fourm's FAQ's for this question and have not seen it covered. You'll might have, I just can't find it.
I have a 2.5 ton 13-seer rheem that's a year old with a 2-bladed condenser fan. It's not real loud but the 2-blades seem to chop the air like a Huey cobra gun ship. Woop, Woop, Woop, etc. The units I've seen with 3-blades seem to have a smoother air draw. Is it possible to convert from 2 to 3 blades, keeping the same pitch and overall surface area the same. I would assume that that would keep the CFM flow the same. Any merit to this idea or am I just talking "Crazy Talk"?
Thanks,
Joe.
Professional Member*
More blades will make for smoother airflow, and better performance against higher static pressures, so would give better airflow as the condenser coil gets dirty.
Typically Rheem/Ruud 2 blade fans only sound very choppy when the condenser coil is dirty. It is how I know one needs to be cleaned, before I even look at it.
Professional Member*
Like Mark said, clean the condenser then decide if you need to change the blade.
I am the "Wally". All others are meer imitations of the original.
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Last edited by beenthere; 08-21-2012 at 05:32 PM. Reason: Non Pro * Member
Professional Member*
You stick a 3 wing on the Rheem factory motor, and I can guarantee you the motor will overheat and shut down, been there done that. It either shuts down because of the weight or the changing of the factory design, don't know but it will shut down with the 1/5 hp motor. Most of the time what your hearing can be eliminated by lowering or raising the blade just a little, this noise is also caused by a dirty coil.
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Is that a 13AJN30 by any chance? If so I can tell you why that POS is noisy!
God Speed, Jim. We'll miss you - 2-26-23
WhoIsThat?, this is the Ask Our Pro's forum, and restricted to only Pro members that have been vetted by the AOPC are allowed post advise, questions or commentary in a thread created by someone else.
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Professional Member*
Adding one more wing to the blade without increasing the horsepower of the motor will overload the motor every time. One more wing flying around is one more surface to move air (and its coinciding drag), so it requires more power to maintain the same RPM.Originally Posted by Mr Bill
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Professional Member*
i concure
it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair
Professional Member*
Yes, you can. BUT the new blade Must have less pitch. And the tech must be good to choose the right blade.
Remember, the manufacture don't go "Ini mini miny mo" and got the blade.
Professional Member*
My 10seer rheem does have that faint helicopter sound.
Does anyone know why rheem is partial to two prop?
Look into a cobra blade from LAU. I think they make two props.
Professional Member*
They say they are quieter because of the 2 blades, but I've heard some pretty loud ones.
Their outdoor fan motors seem to hold up well IMO- compared to other brands.
Professional Member*
+1, it's possible to find a blade that will have the same load at the same motor RPM as your and at the same diameter... but it will take a good tech with a good reference manual and knowledge. Getting the same diameter is important. The location and clearance in refrence to the fan shroud is critical on any fan, centrifugal or axial.
Global Moderator
Still waiting to hear what the unit is?
New Guest
Thanks folks,
Yes the unit's a 13AJN30A01 Value series. I wanted to keep it simple.
So..... Basically if it's not broken don't mess with it.
I do preventative maintenance on the unit, which includes cleaning the condenser and removing debris at end of the cooling season. A fin comb to straighten fins if needed.
Then cover the top with a piece of plywood on stand-offs so the box can breathe.
On a second note: When a systems not running (static), is all the refrigerant in the vapor/gas state? And only becomes liquid after compression and cooling in the condenser pipes? Or does some of the refrigerant stay liquid when the units off?
Again I thank you all for your replies.
Joe.
Professional Member*
The helicopter noise is due to
The manufacturing design of the unit. I'll let baldy elaborate( don't want to steal his thunder)
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Last edited by jpsmith1cm; 08-22-2012 at 09:08 PM. Reason: non AOP member
Global Moderator
Go for it KGod. Glad to see someone besides me knows what the problem is with those units, the 2.5 ton is worse. But you won't stop the chopper sound, sorry
Professional Member*
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Professional Member*
Looking from the top down you will see that air enters the sides, is drawn through the coil and out the top. You will also notice that 1 side has no coil and is blanked off. Another side has 1/2 a coil. Air is drawn through 230 degrees of the coil And 150 degrees of the coil has no airflow. As The blade hits the dead spot it chops the air and you will have noise.
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