Proper way to balance condenser fan?


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Old 07-13-09, 08:46 AM
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Proper way to balance condenser fan?

Hi all,
Love this forum!

My old fan motor blew and I bought a proper replacement with proper capacitor from an online HVAC store. The old GE motor was 1/8 HP with 1075 RPMs, this new one is the same RPMs but it is 1/3 HP. The house cools off fine and nothing seems out of place. Been fine for a full day now.

Installed the motor just fine, everything runs great but there is some wobble now. Not a lot but too much for the long term.

How do I balance the fan properly?

The motor is new (my old one was 1986) and basically the same but the old one had maybe a 3 inch shaft. This new one has maybe an 8 inch shaft.

I took a ruler an mounted the fan about 1 1/2 inches away from the motor...same distance as the old setup. The shaft is fine and there is no wobble or looseness.

I measured the height of the bottom of the blades and the tops of the blades. One blade was off by 1/4 inch on the top part...now it is the same as the others.

I don't know what else to do besides drop the fan to maybe within 1/2 inch of the motor to get it closer???

There are some clip-on weights attached to 2 of the old fan blades for balance..I left them as is...should I remove them?

Should I get a new fan? This old one seems to be just fine and in excellent shape.

Any ideas, tips or techniques would be appreciated. lol
 
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Old 07-13-09, 03:14 PM
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You don't balance a fan blade.Go get another one.You start messing with it you'll probly make it worse or do damage to yourself or the unit.It is balanced at the factory using those clips. You tweaked the blade when you took it off. It happens.I usually replace blade and motor at same time.
 
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Old 07-13-09, 05:33 PM
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OK. Did not know it was necessary. Any recommendation for reasonable prices?
 
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Old 07-13-09, 07:41 PM
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Old motor 1/8, new motor 1/3, that could be trouble soon.
 
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Old 07-14-09, 02:38 AM
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Originally Posted by theapprentice View Post
Old motor 1/8, new motor 1/3, that could be trouble soon.
Yes, it could. Although it seems to defy logic, an underloaded motor can overheat.

Fasco - FHP Replacement Motors - Fasco Facts - Time Saving Motor Replacement Tips
 
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Old 07-14-09, 03:54 AM
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is the outside units fan or the air handlers fan.
 
  #7  
Old 07-14-09, 06:23 AM
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Well, I ordered from a pro HVAC store and gave them the exact make/model etc of the old motor and asked for proper replacement. The person I spoke with was a senior HVAC person. I went with what they recommended. They did not up sell me because the other motor choices were more expensive and price never came up, I just wanted the right product.

@ flirty -

I am speaking of the outside unit
 
  #8  
Old 07-19-11, 07:34 PM
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I did it

I just changed my condensor motor and re-used the fan. It wobbled like crazy. From here on out I am just telling you what I did. I bought six of those super strong magnets that are the size of a nickel (only used 3). I turned off the disconnect and removed an access panel on the side of the unit. Then, turned on the disconnect and slowly moved a sharpy towards the moving fan thinking the heavy side will hit first in hopes of simply putting magnets on the edge of the 2 opposing blades to offset the imbalance. The sharpy idea worked. But, apparently 1075 RPM's creates too much angular momentum for those impossible to get apart magnets. I had to take the top of the unit off again to get them all back. I ended up putting them on the inside (less momentum) about 2 inches from the spline of the motor. After a few tries and a bit of logic, I had to put them on the blade that was being hit with the sharpy, I'm guessing there is some sort of angular momentum lag, or maybe harmonics is involved after a certain RPM as to which blade swings out further. Ended up putting 2 on the heavy blade then repeat process, and 1 on the heavy blade after that. You can now set a beer on that thing and it won't even move. Sharpy is destroyed and a couple welts on my chest from 90 mph magnets.
 
 

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