# Replacement Condensor Fan blade pitch?



## daviesow (Jul 26, 2009)

I have a RHEEM system which is so old the model information is completely worn off. The Compressor Fan motor is seizing up and I am about to replace it. I've selected a suitable replacement motor (Grainger #4UY74) along with a new 3MFD 370V run capcitor. 

Now I need to find the correct fan blades as I am sure the old ones will not come off without damage. They seem to be 18in diameter but I am not sure about the pitch. Looking in the catalog I seem to have a choice of 19 degree or 29 degree pitch (for whatever reason 24 degree does not come in a CCW flavor). 29 degree pitch lists 1/6hp as the minimum necessary and the motor I'm putting in is 1/6 HP.

So the question is, should I select 29deg. for maximum airflow because my motor meets the minimum HP requirement or is that pushing it? should I play it safe with 19deg, less airflow but an easier job for the motor?

Thanks


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## AdRock (Dec 4, 2008)

Pick up a magnetic angle locator from Home Depot, $9. 
http://www.homedepot.com/webapp/wcs...3&productId=100161689&N=10000003+90040+503101

I just replaced my fan and motor. The unit had a 2 blade w/ 27 pitch and I bought a 4 blade with a 30 pitch. Made a huge difference in airflow through the unit. It's been 100F or a little over everyday for the pst month or so. I replaced the fan & motor 2 days ago and the outside unit feels *much* cooler than it did before in the same ambient outside temps.


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## SKIP4661 (Dec 3, 2008)

Could also take the motor to your local hvac co and have them pull it off for you.


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## daviesow (Jul 26, 2009)

AdRock said:


> Pick up a magnetic angle locator from Home Depot, $9.
> http://www.homedepot.com/webapp/wcs...3&productId=100161689&N=10000003+90040+503101
> 
> I just replaced my fan and motor. The unit had a 2 blade w/ 27 pitch and I bought a 4 blade with a 30 pitch. Made a huge difference in airflow through the unit. It's been 100F or a little over everyday for the pst month or so. I replaced the fan & motor 2 days ago and the outside unit feels *much* cooler than it did before in the same ambient outside temps.


To go from a 2-blade 27 pitch to 4 blade 30 pitch you must have upped the HP significantly. The problem for me is that the motor I'm replacing is only about 3 1/2 in. not counting the shaft and the blade is already mounted less than an inch away from the motor. In order to keep the new blade at the same depth (even with the metal fairing) I can't go much bigger. The most I could possibly squeeze in to the space is a 1/5 hp motor which buys me almost nothing as far as more/steeper pitched fan blades.


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## AdRock (Dec 4, 2008)

I see. 

I went from a 1/5 to 1/4 motor to accomodate for the new blade.


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## JohnH1 (Jan 9, 2009)

Not a good idea to increase air flow through the condenser. If it would make the unit run better the manufacturer would have done it. Try and get the correct fan and HP. Just changing the HP with the same fan can also affect performance.


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## biggles (Jan 1, 2008)

give the blade removal a shot ,soak it good from the top of the shaft down into the blade housing....take a channel locks and grab the motor shaft between the fan blade and the top of the motor housing.1/4 turns ccw/cw then keep working it remembering don't grab the blade just the blade housing with your full hand over it....should break loose to full turnns


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## hvaclover (Oct 2, 2008)

http://www.hvacsite.com/f7/blower-wheel-stuck-shaft-152/


check this link for removal of blade.


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## AdRock (Dec 4, 2008)

JohnH1 said:


> Not a good idea to increase air flow through the condenser. If it would make the unit run better the manufacturer would have done it. Try and get the correct fan and HP. Just changing the HP with the same fan can also affect performance.


Could you explain to me the performance difference possibility of the A/C with the different stuff I put in. I'm not trying to argue, just understand what you mean.

I've been an auto mechanic for years have never had a problem with a bigger fan & more airflow through a condensor.

My thinking in what I did was this. There are so many manufacturers out there that will put the bare minimum needed to have everything work properly in order to keep their price down, or to keep the price the same and get a better profit margin. I only went up slightly in HP which is still within the power output available. Also, there were no 2 or even 3 blade fans in stock that I could find. It was going to take a few days to get it here. The 2 blade that I had had a big chunk taken out of it. It was way out of balance and vibrating the whole unit like mad. I couldn't put that on the motor. So I got what I could get right then. 
I'm just a little lost on why a little extra cooling on the condenser would harm A/C performance.


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## hvaclover (Oct 2, 2008)

Because it plays hell with the the subcooling of the liquid refrig. You cool it down too much it will turn to flash gas at the metering device.


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## glambert25 (Jun 20, 2012)

how do i know what is the correct oem fan blade for my condenser motor


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## hvac instructor (Jun 8, 2012)

to get a stuck blade off i cut the shaft between the motor and blade.
motor is junk anyhow. then cleen the shaft with emory cloth and put on top of a vise jaws so when you hit the shaft it goes between the jaws while the blade sits on top. use a brass hammer or a punch that is smaller than the shaft. i file any rough spots on the shaft also. also use WD40 or other brands.


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## fixitman48 (May 11, 2015)

hvaclover said:


> Because it plays hell with the the subcooling of the liquid refrig. You cool it down too much it will turn to flash gas at the metering device.


Sorry, but it will actually do the opposite. More air flow will increase subcooling = cooler liquid refrigerant = less chance of flashing. 

Condenser fan uses a bit more energy, the compressor uses a bit less. Probably an efficiency improvement. To take best advantage of the more efficient condenser, you might have to adjust the refrigerant charge, since the subcooling and the superheat tend to change together if you do this with fixed orifice systems. To get it just right, you might also have to adjust metering. Everything is a balance in sorting these issues out. How much do you want to experiment? 

It might mess with performance in other ways - such as at low outdoor ambient temperature - especially if the system uses a cap-tube or other fixed metering device. That happens because the high-side pressure is lowered when there is more subcooling, leading also to a colder evaporator. With too much condenser air flow, a unit that would have frozen its evaporator coil at 50* outside might freeze it at 55* instead, because the evaporator's entering vapor temperature is lowered. If it goes below 30* - you can make ice. 

Best fix for that? Turn off your AC and open the windows.


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## beenthere (Oct 11, 2008)

5 1/2 year old thread.

Thread closed.


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